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The most important direction of the climate agenda is the creation of efficient hydrogen production technologies. The most important direction is the production of hydrogen from biomass. The aim of this work is to investigate how particle parameters (diameter and density) affect the maximum particle volume concentration at which a stable flow regime is achieved in steam gasification that produces hydrogen-rich syngas. Computational fluid dynamics (CFD) methods were used to analyze the flow around two sequentially arranged bodies. A comparative assessment was conducted to determine the conditions under which hydrodynamic instability may occur in low-concentration gas-dispersed flows. Variations in the physical properties of particles, typical of those found in industrial biomass and fossil fuel energy installations, were considered in this assessment. The numerical model for laminar flow around individual particles was validated using the experimental data of Rowe and Henwood for dimensionless intersphere distance of 5, 11, 17, and 23. It was demonstrated that the velocity profile upstream of the first sphere influences the ratio of forces acting on each sphere. The critical dimensionless center-to-center distance (x / d) cr was calculated, at which the ratio of the force acting on the second particle (F 2) to that on the first particle (F 1) equals 0.95 (indicating the onset of convergence), under steady uniform gas flow conditions in an elemental streamtube of an ideal entrained-flow reactor for particles of spherical and plate-like shapes. Within the Reynolds number range 2.0·10−1 ... 3.2·103, the influence of particle density, size, and shape on the corresponding critical volume concentration φ cr and (x / d) cr was determined. Additionally, for spheres, the force ratio F 2 / F 1 = 0.90 was considered, which allowed to establish the transition zone between entrained-flow systems and circulating fluidized bed (CFB) boilers. Simulations of gas flow around two plates with three different orientations relative to the incoming flow were conducted. The results demonstrate that the mutual orientation of plate-like particles in the flow affects their hydrodynamic interaction. Specifically, compared to the scenario of flow around two spheres of equivalent diameter, the risk of convergence increases when the particles are oriented with their largest face perpendicular to the incoming flow, and decreases when they are oriented with their smallest face perpendicular to the incoming flow. The effectiveness of the proposed method was verified by analyzing a range of systems, including power boilers, industrial gasifiers, and large-scale test installations. (provided to the authors on 27.12.2024 for printing in IJHE from the archive of Fermaltech Montenegro Limited, made by A.L. Gusev using Designer. On the DALL E 3 platform.). [Display omitted] [ABSTRACT FROM AUTHOR]

The translational effects of gas streams, which form after the triple-shock configurations at Mach reflection of blast waves with normal main shock (so-called stationary Mach configurations), were analyzed. Unlike in the case of an elevated explosions of fuel as rocket starts in initially stagnant air, which is considered here as a private case, it was supposed that this shock-wave structure moves in a preceding flow with arbitrary velocity (and corresponding flow Mach number). Analyzing relations of the dynamic pressures across the slipstream, which emanates from the triple point of the Mach reflection, it was shown that the flows after the triple-shock configuration usually differ much in their translational action on surrounding objects. It was found and discussed that some configurations drag the objects initially situated above and below the triple-point trajectory in opposite directions. Moreover, the "trigger" structure was found that remains previous flow drag action on the object above the triple-point trajectory, but switches it to exactly opposite one, if the object is situated below the triple point. • Triple-shock configurations appear at the internal blast inside of a spaceship. • They divide gas stream into two regions with very different velocity pressures. • Blast safety of an object aboard depends on its position above or below triple point. • Triple configurations are found with extreme drag force above or below the slipstream. • Some of them drag objects above and below the slipstream in opposite directions. [ABSTRACT FROM AUTHOR]

One of the important tasks of space flight safety is the ability of a wing to maintain stability in an oncoming turbulent flow. In this case, the spacecraft must move the greatest distance. The paper studies the motion of a thin plate near a boundary in an oncoming flow of rarefied gas. At low Reynolds numbers, the effect of the boundary on the plate is studied, and the possibility of self-propulsion is shown. • The drag force of the plate increases sharply as the distance to the boundary decreases. • The lifting force and moment change from the center of the plate to the boundary decreases. • The point of application of the resultant force shifts to the rear edge of the plate. • Self-motion is possible for plates that have a common rib. [ABSTRACT FROM AUTHOR]

The radiation coming from the Sun heats the Earth's atmosphere and generates atmospheric tides. In this paper, we model atmospheric tides in the presence of background wind and dissipation processes and investigate their effects. The equations for tidal oscillations of wind and temperature in the atmosphere encompass factors such as background wind, temperature profile, and background composition including ozone, carbon dioxide, hydro-magnetic interactions, Newtonian cooling, eddy, and molecular diffusion. These components interact to define the behavior of tidal phenomena comprehensively. Thermal forcing processes include the insolation absorption of H 2 O in the troposphere, O 3 in the stratosphere, and a contribution from O 2 absorption in the thermosphere. The method of solution for the equations is outlined for the solar diurnal tides during the March equinox by considering all these dissipation processes and the background wind. The obtained results are in good agreement with the Global Scale Wave Model (GSWM-00). It is found that the background wind plays significant role in affecting the horizontal wind oscillations below 100 km. At higher altitudes (100–200 km), the background wind, ion drag force, divergence of momentum, and heat fluxes due to molecular and eddy diffusion have a considerable role in affecting the zonal and meridional winds. [ABSTRACT FROM AUTHOR]

A major challenging proffered study rely on the inquisitive optimization of entropy together with thermal as well as mass transportation towards the chemically reactive 3-D Prandtl liquid under consideration of applied magnetic field, variable thermal conductivity and also diffusivity, hall current together with ion slip features, viscous dissipation and heat generation. Moreover, in present research study, model such as Cattaneo Christov heat flux was implemented in order to explore the thermal relaxation characteristics. By employing correspondence transformations, the system of modeled equations modified into non-linear ODEs system. The Optimal Homotopy Analysis methodology (OHAM) was adopted to solve the proffered problem. The influential arising constraints demeanor within both velocities (horizontal as well as vertical), temperature and concentration profiles were discussed and also shown graphically. Moreover, outcomes of diverse parameters were also examined and presented graphically within the entropy formation rate and also Bejan number. The effects of implanted factors across the drag force, the rate of thermal as well as mass transportation are accessible in current study via tables and validate the obtained results. Both velocity profiles (horizontal as well as vertical) decreased for increment in Hartman number whilst opposite demeanor seen for other considered constraints. Temperature profile drops for Prandtl number and elastic constraints whereas enhanced for other influential considered parameters whilst concentration profile augmented with Prandtl number. Present problem novelty relies on the modeling of comprehensive system of equations which modified into nonlinear ODEs. In order to obtain the solution numerically, technique such as Optimal Homotopy was opted. [ABSTRACT FROM AUTHOR]

Satellites in very low Earth orbits can leverage the aerodynamics forces for control purposes. Three-axis attitude control can be achieved by adjusting the orientation of aerodynamic surfaces, benefiting from both drag and lift forces. However, complete control over the orbital motion of a satellite is unattainable using aerodynamic forces alone, as positive thrust cannot be generated. Nonetheless, this limitation does not apply when focusing on the control of a satellite formation. By properly modulating the orientation of panels, positive and negative relative forces can be generated. This paper shows that even in a formation of simple microsatellites, it is possible to achieve formation and attitude simultaneous control by using no other actuators than the aerodynamics surfaces. • Very Low Earth orbits are appealing but the large atmospheric density can be a problem. • The atmospheric forces can be used for control purposes. • Formation control and attitude control can be individually realized by using aerodynamic forces. • A GNC architecture is implemented to realized both goals with the same aerodynamic actuators. • Performance in keeping or acquiring a desired state (attitude and relative position) is promising. [ABSTRACT FROM AUTHOR]

Transport of particles in flows is often modeled in a combined Eulerian–Lagrangian framework. The flow is evaluated on an Eulerian grid, while particles are modeled as Lagrangian points whose positions and velocities are evolved in time, resulting in particle trajectories embedded in the time-dependent flow field. The method essentially resolves the flow field in complex geometries in detail but uses a closure model for the particle dynamics aimed at including the essential particle–fluid interactions at the cost of detailed small-scale physics. Rarefaction effects are usually included through the phenomenological Cunningham correction on the drag force experienced by the particles. In this Lagrangian point-particle approach, any explicit reference to the finite size and the shape of the particles, and their local orientation in the flow field, is typically ignored. In this work we aim to address this gap by deriving, from fully-resolved Direct Simulation Monte Carlo (DSMC) studies, heuristic or closure models for the drag force acting on prolate and oblate spheroidal particles with different aspect ratios, and a fixed orientation, in uniform ambient rarefied flows covering the transition regime between the continuum and free-molecular limits. These closure models predict the drag in the transition regime for all considered parameter settings (validated with DSMC data). The continuum limit is enforced a priori and we retrieve the free-molecular limit with reasonable accuracy (based on comparisons with literature data). We also include in the models the capability to predict effects related to basic gas-surface interactions via the tangential momentum accommodation coefficient. We furthermore assess the validity of the proposed closure model for particle dynamics in proximity to solid walls. This investigation extends our previous work, which focused on small aspect ratio spheroids with exclusively diffusive gas-surface interactions [see Livi et al. (2022)]. The derived models are obtained for isothermal, subsonic flows relevant for particle contamination control in semiconductor manufacturing. • DSMC-enhanced drag force closures for particle tracking under rarefied gas conditions. • The drag force on finite-size spheroids in the transition regime of rarefied flows. • Towards algorithms for particle contamination control in semiconductor manufacturing. • Covering the device-to-nanoparticle scale separation in high-tech equipment. [ABSTRACT FROM AUTHOR]

Recently, researchers are facing great challenges to form the homogeneous solutions of various liquids at biomedical and industrial levels. Such homogeneous solutions can be controlled through stratification phenomenon directly which is ignored by the researchers in the existing literature specifically quadratic stratification and melting heat mechanism which is valid only for higher temperature processes. Thus, to form the homogeneous and stable liquid solutions for various industrial processes, we investigate the melting heat phenomenon in quadratic stratified Jeffery Nano fluid flow deformed due to linearly stretching sheet along with stagnation point. Inclined constant magnetic field is implemented on the fluid through an arbitrary angel. Characteristics of heat and transportations are disclosed through viscous dissipation, Brownian motion and thermphoresis. Temperature and concentration of the surrounding fluids are assumed higher than the stretching surface. The resultant governing equations are reduced to ordinary differential equations through proper transformations. Convergent analytical series solutions are computed via homotopic approach. Impact of various emerging parameters on temperature, velocity and concentration fields are illustrated and discussed comprehensively. Sherwood and Nusselt numbers and drag force are scrutinized mathematically, physically and graphically. It is analyzed from the study that (i) dominant melting reduces the temperature field (ii) higher thermal and solutal stratification decay the temperature and concentration fields respectively (iii) higher thermophoresis enhances the temperature field. Further, it is concluded that stable and homogeneous solutions may be made by increasing melting and reducing stratification phenomena. This study will help us to provide actual amount of heat for heating processes in industries and biomedicine which is the basic requirement for excellent quality of products. [ABSTRACT FROM AUTHOR]

Understanding particle ejection behaviours in plume-regolith interaction is important for a safe soft-landing system and landing manoeuvre in planetary missions. In this study, a Mach 5.8 hypersonic jet at the different Reynolds numbers of 2.58 × 104 and 9.35 × 102 impinges on the deposited glass particles of 80 μm diameter in a vacuum chamber, and the particle and gas motions at the nozzle pressure ratios (NPR) of 95, 950, and 1900 are investigated using the time-resolved PIV and high-speed Schlieren techniques. A narrow hypersonic jet consisting of several shock cells forms at the lower NPR of 95 and causes a deeply narrow crater due to its jet penetration into the deposited particles. The deeply narrow crater makes a particle ejection angle increase upwardly. On the other hand, a relatively wide crater forms due to the jet impingement at the other NPR conditions which a widely long shock cell is generated. Based on the present experimental results, a dominant factor in particle ejection angle is the crater size and depth, whereas a particle diffusion velocity is dominated by surrounding pressure. The diffused particles move faster in a low surrounding pressure because of a low aerodynamic drag force acting on the diffused particles. • A dominant factor in particle ejection angle is the crater size and depth. • The diffused particles move faster in a low surrounding pressure. • The particle and gas motions at several NPRs are investigated in a vacuum chamber. [ABSTRACT FROM AUTHOR]

A comprehensive study of the nature of micropolar fluid on an unsteady MHD-free convective transference through a perforated sheet is discussed considering the suction and Lorentz's force effects. The corresponding similarity equations of temperature, momentum, concentration, and angular momentum equations have been modified into the non-dimensional similarity equations of the temperature, momentum, concentration, and angular momentum equations by utilizing the similarity technique. The modified equations have been resolved by exerting the shooting technique with the help of the finite difference method (FDM) through MATLAB. The fluid flow is inversely proportional to the changes in micro rotational effect (Δ). The concentration boundary layer gets thinner as the Schmidt number (Sc) advances and hence the concentration of the fluid decreases. Micropolar fluid helps reduce drag forces and also acts as a coolant. The heat transmission rate advances by around 391%, and 110% due to growing amounts of Pr from 0.71 to 7.0, and v 0 from 0.6 to 3.0, respectively. The surface couple stress decays by about 33%, 45%, and 36% due to increasing values of M from 0.6 to 3.6, ∆ from 3.0 to 6.0, and λ from 0.1 to 1.2, respectively. [ABSTRACT FROM AUTHOR]

Understanding the dynamic response of trees to a strong wind is crucial to alleviating the damages and losses of tree forests caused by windstorms. Previous studies have elucidated small deformations of a broad range of tree species, yet mathematical models that can accurately pinpoint the location and severity of wind-induced damages are still lacking. To bridge this gap, the present work puts forward the first geometrically accurate, physics-based model to capture large deformation of trees induced by a strong wind. The proposed model incorporates a branched tree architecture to represent the topology of a realistic tree. The large, dynamic deformation of the trunk and branches of the tree is described by a system of nonlinear partial differential equations derived from structural theories rooted in classical mechanics. The aerodynamic loading is quantified based on the instantaneous relative velocity between the wind and the tree. The proposed model could successfully reproduce the effects of aerodynamic damping by capturing the nonlinear interplays between the wind and the tree, in contrast to prior analytical models that relied on empirical assumptions of the damping coefficients. The model further reveals a reduction in the drag force due to wind-induced shape reconfiguration, which is enhanced exponentially as a function of the wind speed. The proposed modeling framework could aid in the development of novel forest management strategies to mitigate wind-induced economic and environmental losses. • Quantifying the large dynamic deformation of trees in a strong wind is essential to mitigating wind-induced damages. • This work puts forward the first geometrically accurate, physics-based model to capture the large deformation of trees. • The model incorporates branched tree architectures and structural theories rooted in classical mechanics. • The model accurately captures the effects of aerodynamic damping without empirical assumptions on the damping coefficients. • The analysis reveals that drag reduction enhances exponentially with respect to the wind speed due to shape reconfiguration. [ABSTRACT FROM AUTHOR]

• The measurement of total flow resistance with a novel drag plate system. • Analysis of the effect of emergent or submerged canopies on the total flow resistance. • Accurate estimation of the total flow resistance parameters with simple relations. In canopy flows, flow resistance mainly originates from vegetation drag and depends on vegetation characteristics and flow conditions. In the present study, a series of experiments were performed in various hydraulic scenarios with high stem Reynolds numbers (2641 ≤ Re d ≤ 17333) using relatively sparse rigid canopies, represented with four different dimensionless vegetation densities (0.0044, 0.0098, 0.0174 and 0.0392), on a smooth bed. A novel drag plate mechanism was developed to measure the total flow resistance due to the emergent and submerged vegetation arrays in a staggered pattern under subcritical flow conditions. Manning's roughness coefficient and Darcy–Weisbach friction factor were adopted to represent the total flow resistance in the analyses. Simple empirical relationships based on roughness concentration and submergence ratio were derived to determine the total flow resistance parameters within a broad range of stem Reynolds numbers. Although relationships were proposed in a simple form to be used for direct practical applications, they show similar or better performance in the prediction of total flow resistance parameters than the existing equations in the literature, which require considerable computational effort. Additionally, analyses demonstrated that the results of the present study and those of similar studies regarding canopy flow resistance are in good agreement. Accordingly, the novel drag plate looks promising for measuring flow resistance due to vegetation and bed conditions similar to those in nature. [ABSTRACT FROM AUTHOR]

Deep reinforcement learning (DRL) is gaining attention as a machine learning tool for effective active control strategy development. This study focuses on employing DRL to develop an efficient active control strategy for flow around three circular cylinders arranged in an equilateral-triangular configuration in a two-dimensional channel. The analysis of control outcomes reveals that DRL induces vortices of varying sizes between the cylinders, resulting in large elliptical vortices at the rear. This enhancement in flow stability leads to a significant 40.40% reduction in cylinder drag force and an approximate 8.23% decrease in overall drag oscillations. Our research represents a pioneering application of DRL for stabilizing complex flow around multiple cylinders, yielding remarkable control effectiveness. The noteworthy outcomes in controlling the stability of complex flows highlight the capability of DRL to grasp intricate nonlinear flow dynamics, showcasing its potential for investigating active control strategies within complex nonlinear systems. [Display omitted] • Demonstrating deep reinforcement learning in non-linear, complex flow problems. • Remarkable 40.40% drag reduction, 8.23% less overall drag fluctuations. • Efficient implementation of real-time, multi-point active control for complex flow. [ABSTRACT FROM AUTHOR]

• Operando observation system is developed to make in-situ test on lab-on-a-chip. • Actual evolution process of charged submicron particles is recorded intuitively. • This work demonstrates direct influence of drag force on particle chain fracture. • It is first-time visualization of mechanism elucidation of particle re-entrainment. Inhalable particle is a harmful air pollutant that causes a significant threat to people's health and ecological environments, which should be removed to purify air, but there exists limited removal efficiency due to particle re-entrainment. Here, Operando observation system based on microscopic visualization method is developed to make in situ test of particle migration, deposition and re-entrainment characteristics on a lab-on-a-chip to achieve the investigation in micro-level scale. The deposition evolution of charged particles is recorded in electric field region intuitively, which confirms the fracture of particle chain occurs during the growth process of deposited particles. It captures the instantaneous process that a larger particle with micron size due to the coagulation of submicron particles fractures from main body of the particle chain for the first time. The analysis of migration behavior of a single submicron particle near electrode surface demonstrates the direct influence of drag force on the fracture of particle chain. This work is the first-time visualization of dynamic process and mechanism elucidation of particle re-entrainment at the micron level, and the findings will provide the theory support for the particle re-entrainment mechanism and bring inspires of enhancing capture efficiency of inhalable particle. [Display omitted] [ABSTRACT FROM AUTHOR]

In recent years, magnetoactive soft continuum robots (MSCRs) with multimodal locomotion capabilities have emerged for various biomedical applications. Developments in nonlinear dynamic models and effective control methods for MSCRs are deemed vital not only to gain a better understanding of their coupled magneto-mechanical behavior but also to accurately steer the MSCRs inside the human body. This study presents a novel dynamic model and model-based AI-driven control method to guide an MSCR in a fluidic environment. The MSCR is fully exposed to fluid flows at different rates to simulate the biofluidic environment within the body. A novel nonlinear dynamic model considering the effect of damping and drag force attributed to fluidic flows is first developed to accurately and efficiently predict the response of the MSCR under varying magnetic and mechanical loading. Fairly accurate correlations were observed between the theoretical responses based on the developed magneto-viscoelastic model and the experimental data for various scenarios. A novel model-based control algorithm based on a fractional-order sliding surface and deep reinforcement learning algorithm (DRL-FOSMC) is subsequently developed to accurately steer the magnetoactive soft robot on predefined trajectories considering varying fluid flow rates. A fractional-order sliding surface and a compensator, trained using the deep deterministic policy gradient algorithm, are designed to mitigate the amount of chattering and enhance the tracking performance of the closed-loop system. The stability proof of the developed control algorithm is also presented. A hardware-in-the-loop experimental framework has been designed to assess the effectiveness of the proposed control algorithm through various case studies. The performance of the proposed DRL-FOSMC algorithm is rigorously assessed and found to be superior when compared with other control methods. • Developing a computationally efficient model for magnetoactive soft continuum robots, accounting for damping and drag force. • Formulating an AI-driven fractional-order sliding mode algorithm to guide the robot on trajectories amid fluid flow rates. • Introducing a deep reinforcement learning-based compensator to cope with unmodeled dynamics and uncertainties of the robot. • Designing an optimal fractional-order sliding surface for control performance improvement. • Fabricating the magnetoactive soft robot and conducting a HIL experimental study to control it under varied fluid flow rates. [ABSTRACT FROM AUTHOR]

Objects in Low-Earth Orbit (LEO) experience a range of environmental conditions that influence their trajectories. Aside from gravitational effects and solar radiation pressure, drag due to the residual background atmosphere is conventionally viewed as the primary perturbing factor. The ionosphere is an additional background environment composed of charged particles that is well-known to result in spacecraft charging, and in the worst case, cause arcing or unwanted electrostatic discharges. While the ionospheric plasma density is typically an order of magnitude (or more) lower than the atmospheric neutral gas density, electrostatic charging can lead to the formation of plasma sheath and wake structures around an object that artificially increase its effective collecting area. Direct charged particle collection and indirect charged particle deflection gives rise to a drag force that can exceed that due to atmospheric neutral gas alone at some altitudes and charging potentials. Here, we present a model accounting for charged particle flow effects (i.e. charged aerodynamics) around objects in LEO, and validate this model with previous particle-in-cell simulations and experiments. Using atmospheric properties from the Mass Spectrometer and Incoherent Scatter radar (MSIS) model and ionospheric properties from the International Reference Ionosphere (IRI), we show that plasma-induced drag in LEO can be significant and may have important orbit prediction implications for space domain awareness and space traffic management. Through differential spacecraft biasing, ionospheric plasma drag can also be used as a propellantless and "solid-state" mechanism to achieve in-orbit mobility for precision maneuvers, formation flying, deorbiting, and even partial attitude control. [Display omitted] • Charging in the ionosphere generates electrostatic fields around spacecraft. • Collection/deflection of charged particles produces a drag force. • Sheath expansion increases the effective collecting area, amplifying plasma drag. • Plasma drag is an additional environmental disturbance affecting spacecraft motion. • Plasma drag can be exploited as a propellantless propulsion mechanism. [ABSTRACT FROM AUTHOR]

We consider a problem occurring in a magnetostatic levitation. The problem leads to a linear PDE in a strip. In engineering literature a particular solution is obtained. Such a solution enables one to compute lift and drag forces of the levitating object. It is in agreement with the experiment. We show that such a solution is unique in a class of bounded regular functions. Moreover, as a byproduct, we obtain nonstandard uniqueness results in two linear PDEs in unbounded domains. One of them is an eigenvalue problem for the Laplacian in the strip in the nonstandard class of functions. [ABSTRACT FROM AUTHOR]

Present work is concerned with hydromagnetic bioconvective chemically reactive flow of Reiner-Rivlin nanoliquid. Analysis is constructed for entropy generation. Thermal relation consists of Joule heating, radiation and dissipation. Soret effect for chemically reactive flow is examined. Nonlinear governing systems after adequate transformations are solved by ND-solve technique. Graphical analysis for velocity, microorganism field, entropy rate, thermal field and concentration is analyzed. Graphical description for coefficient of skin friction, microorganism density number, heat transport rate and concentration gradient are studied. Entropy rate increase is detected for higher magnetic parameter while reverse trend holds for velocity. Clearly temperature augments against thermophoresis and radiation. Radiation intensifies entropy rate and heat transport rate. Similar impact of drag force and temperature for magnetic parameter is noticed. Concentration and mass transport rate rise against higher Soret number. Brownian motion variation results in concentration decays. Large Peclet number leads to decrease of microorganism field whereas it intensifies the microorganism density number. [ABSTRACT FROM AUTHOR]

• A novel model of using nSFEM and DPM to solve particle-laden flows. • The super robustness in handling extremely distorted polygonal meshes of the present method. • The unified implementation of mean value coordinates interpolation as shape function and fluid drag interpolation with high-fidelity. • The polygon mesh in this paper shows a great adaptation to complex geometry. In this work, an n-sided polygonal smoothed finite element method (nSFEM) using mean value shape function for concave polygonal element coupled with the discrete phase model (DPM) is developed to solve particle-laden flows. The fluid phase is solved using nSFEM stabilized by the well-developed characteristic-based split (CBS) algorithm. The concave polygonal element is successfully constructed via the intrinsic characteristic of mean value shape function and a new smoothing domain (SD) construction with more physical meaning; thus, addressing the severely distorted local mesh, as well as retaining good geometric adaptability. In the meantime, the modeling of the coupling between the fluid and the particle is achieved by reusing the mean value interpolation to obtain the fluid drag force acting on the particle. The accurate capture of fluid velocities at particle positions within arbitrary polygonal elements via mean value interpolation ensures fluid drag with high-fidelity. Several classical numerical examples, including particle-laden flow around a circular cylinder, are presented to demonstrate the high accuracy and good robustness, and the capability of the proposed method for predicting particle motion in the analysis of complex particle-laden flows. [ABSTRACT FROM AUTHOR]

With the continuous increase of train speeds, the aerodynamic drag force provided by aerodynamic braking plates can effectively solve problems of insufficient emergency braking force. The newly proposed aerodynamic braking plates installed in the inter-car gap (ICG) avoid the destruction of the carbody's strength. In this study, a numerical simulation model of a four-car marshalling train with a speed of 300 km/h is established to study the effect of installation position and opening height of the braking plates mounted in the ICG on the aerodynamic characteristics. The aerodynamic characteristics of the braking plate installed upstream and downstream of the ICG were investigated separately. The downstream plate, which showed better braking performance, was further studied at plate heights of 200 mm, 400 mm, 500 mm, 600 mm, and 800 mm. Results indicate that compared to upstream plates, the aerodynamic drag force coefficient generated by the downstream plates increased by 13.2%. The aerodynamic resistance of the train and the aerodynamic lift of each car increased gradually as the height of the downstream plates increased. Additionally, the braking plate in the ICG had limited anti-crosswind capabilities, with its braking effect significantly weakened in a crosswind of 10 m/s or higher. These results will serve as a guide for the design of aerodynamic braking plates for high-speed trains. [ABSTRACT FROM AUTHOR]

The magnetic field condition has a great influence on the magnetic control drag of reentry vehicle, so it is an important research topic to select appropriate magnetic field condition to control the drag force of vehicle. This paper analyzes the magnetic control drag by solving the hypersonic magnetohydrodynamic equations and combining the magnetic field working conditions, studies the influence of the axisymmetric magnetic field direction on the drag, supplements the mechanism of Lorentz force, pressure and conductivity on the axisymmetric magnetic control drag, and compares the drag value and drag composition ratio under different magnetic field directions. The problem is solved numerically for a particular model of a dipole magnetic field. Under different dipole magnetic fields, the magnitude and distribution shape of Lorentz force are different. There are several dividing lines where the Lorentz force is 0, and the Lorentz force directions on both sides are opposite, and this line divides the Lorentz force field into multiple parts. In addition, it is found that the change of the angle between the axis of the aircraft and the direction of the magnetic field will cause the change of the aircraft resistance, which will reduce or increase it. • The deflected magnetic field can produce greater resistance. • The mechanism of aircraft magnetic resistance is supplemented. • The magnetic resistance and its composition in different magnetic field directions are calculated. [ABSTRACT FROM AUTHOR]

Motion of a solar sail or a spacecraft equipped with a solar sail is one of the interesting problem of celestial mechanics. This paper deals with stationary solution of solar sail problem with radiating first primary and triaxial second primary under the frame of circular restricted three body problem (RTBP). First, equations of motion is derived with triaxiality and sail lightness number and then artificial equilibrium points (AEPs) are determined. It is noticed that impact of triaxiality parameters (σ 1 and σ 2) of second primary is less than that of sail lightness number (β) due to which a considerable deviations in the positions of AEPs are occurred. Further, linear stability test is performed for all AEPs and it is found that similar to equilibrium points in classical RTBP, collinear AEPs are unstable for all mass parameter μ ∈ (0 , 1 / 2 ] and triangular AEPs are stable in the range 0 < μ < μ c = 0.03758902. Moreover, stability range decreases with the values of β and σ 1 but increases with σ 2 . After this we analyze the periodic orbits of the solar sail in the vicinity of AEPs and it is noticed that nature of motion is unaffected but time period is influenced from the sail number β and triaxiality parameters σ 1 and σ 2 . The findings are useful to describe the more generalized solar sail problem with other perturbations such as oblateness, albedo, drag forces etc. [ABSTRACT FROM AUTHOR]

• The original design of the plow-subsoiler-fertilizer. • Deep loosener combined with a reversible plow. • Soil fertilization is combined with the process of its cultivation. • Vibratory subsoiler reduces drag force. • Calculated optimal design parameters. The use of intensive technologies for the cultivation of agricultural crops provides for the application of fertilizers in the process of tillage. This reduces the compaction of the soil, increases its fertility and the quality of the crop. The purpose of these studies is to develop a universal working tool that allows you to combine several technological operations in one pass of the unit. The authors have developed an original design of a plow-subsoiler-fertilizer. This combined working body includes a reversible plow and a vibratory subsoiler with fertilizer ducts. This solution allows you to combine the application of fertilizers when plowing the field, loosening the subsoil layer and mixing the soil. As a result of the work, the dependences of the geometric dimensions of the structure on the traction resistance to movement in the soil were obtained. To implement the developed idea into a real design, the main parameters of the plow-subsoiler-fertilizer are determined. Particular attention is paid to the calculation of the spring mechanism that ensures the vibration of the subsoiler. The optimal number and location of belleville springs in the block and shock absorber were selected, at which the subsoiler will perform self-oscillations with a given amplitude. [ABSTRACT FROM AUTHOR]

The increase in offshore exploration for oil and natural gas has raised concerns about the safety of pipelines in the face of submarine slides, debris flow, and high-density turbidity currents. These submarine gravity flows constitute significant marine geohazards as they undermine the structural integrity of offshore pipelines, underscoring the importance of understanding the complexities of the dynamic interaction process. We herein present a comprehensive review of the complex interactions between submarine gravity flows and offshore pipelines. Emphasis is on the influence of pipeline characteristics, environmental factors, and flow properties on the impact force exerted on the offshore pipeline and the overall interaction process. Recent literature indicates that implementing modified pipeline designs, such as streamlined shapes and advanced design materials, can effectively minimize drag and lift forces, thus potentially reducing the risk of damage by submarine gravity flows. This underscores the need to combine sophisticated engineering designs and durable materials to protect offshore pipelines. This paper provides an in-depth understanding of the interaction between submarine gravity flows and pipeline infrastructures, suggesting the implementation of real-time monitoring technologies, novel pipeline materials, and the adoption of innovative designs that can withstand adverse seafloor environments and effectively mitigate the risk of sediment-induced damage in landslide-prone regions. The article summarizes existing knowledge on mitigative technologies and recommends areas for further investigation to improve the safety and durability of submarine pipelines. • The paper reviews the interaction between submarine gravity flows and offshore pipelines with emphasis on the impact forces. • Recent advances in lab and numerical analysis, offering valuable insights for safer offshore pipeline design, are highlighted. • The effectiveness of pipeline designs in reducing impact forces and enhancing resilience to marine geohazards is discussed. [ABSTRACT FROM AUTHOR]

• The effect of mesh orientation on the hydrodynamics of a moving trawl structure and its fluttering motions were experimentally studied. • Relationship between hydrodynamic force and trawl motion of trawl structures with T0 and T90 mesh were evaluated and discussed. • The nonlinear dynamics of trawl net using the Hilbert–Huang transform (HHT) was examined. • The inherent characteristic oscillation of the drag force response for the trawl structures are synchronized with both the low-frequency characteristic of surge and heave motions. Although adopting the T90 mesh orientation on the trawl net can improve the selectivity of the trawl codend, it is unknown whether the T90 mesh orientation influences the dynamic behavior of the trawl system. Therefore, this study uses non-linear dynamic analysis to examine the effect of mesh orientations, mesh size, and twine diameter on the mesopelagic trawls' fluttering motions and hydrodynamic force responses. Three trawls are designed with different mesh orientations (T0 and T90), mesh sizes (40 mm and 60 mm), and twine diameters (0.96 mm and 1.11 mm) on the codend and codend extension sections of the trawl model based on Tauti's law. These trawls are tested in a flume tank under various flow velocities and catch sizes. A time-frequency analysis method based on the Hilbert–Huang transform is utilized to analyze each trawl's dynamic responses, including motions and drag force responses. The results are compared with those obtained through Fourier analysis using power spectral density. The results highlight that the oscillation amplitude of the surge motion of the T90 trawl is higher than that of the T0 trawl. In contrast, the T90 trawl's heave motion oscillation amplitude is smaller. The dominant frequency of the periodic high-energy coherent structures of the surge and heave motions are detected at a low frequency. The surge and heave motions of the T0 trawl have a greater response to the current components with lower frequencies than that of the T90 trawl. An increase in mesh size, a decrease in twine diameter, and a change in mesh orientation decrease the drag force. The inherent characteristic oscillations of the drag force response for the three trawl models are synchronized with the low-frequency characteristic of surge and heave motions. The gravity periods of the low-frequency mode components of drag force, surge motion, and heave motion for the T90 trawl are higher than those for the T0 trawls. In other words, the T90 trawl is more stable and selective than the T0 trawl. The findings of this study offer important information for comprehending and enhancing the selectivity of trawls in marine mesopelagic fisheries, particularly for exposing the effects of mesh orientation and design parameters on trawl performances. [ABSTRACT FROM AUTHOR]

The design of the cathode flow field plays a relevant role in the performance of proton exchange membrane fuel cells (PEMFC). Recently, porous flow fields have emerged as an alternative to conventional rib/channel flow fields (e.g., serpentine flow field) in an attempt to increase PEMFC performance. In this work, we aim to shed light on pros and cons of both bipolar plate types by analyzing transport through porous and rib/channel flow fields using experimental and numerical work. The experimental polarization curves and oxygen transport resistance data of a cathode porous flow field are used to validate the numerical model. Then, a comprehensive parametric study of the model is presented, involving both operating and constructive parameters. The results show that the main advantages of porous flow fields are: (i) the improvement of oxygen transport, (i i) the decrease of flooding in the cathode MEA, and (i i i) the increase of the distribution homogeneity in the in-plane direction of physical parameters (e.g., current density and temperature). In contrast, the main disadvantages are: (i) the potential effect of electrical contact resistances between porous surfaces, and (i i) the decrease of the water removal drag force in the cathode channel. The above two issues can be mitigated using: (i) thinly manufactured foams and/or increasing the assembly compression, and (i i) hybrid porous flow fields that incorporate a rib/channel pattern with fine pore-size porous ribs. [Display omitted] • Pros/cons of cathode porous flow fields are examined with a validated model. • Oxygen transport is enhanced, MEA saturation reduced, and homogeneity increased. • Ohmic contact resistance and water accumulation in flow field reduce performance. • Thin and highly compressed foams can mitigate the above adverse effects. • Combination of rib-channel/porous flow fields can also provide a good design trade-off. [ABSTRACT FROM AUTHOR]

This study explores the design and application of Kresling origami structures for efficient one-way airflow control in intelligent ventilation and air flow regulation. The mechanical properties of the Kresling origami structure were examined using the finite particle analysis and the finite element method. The Kresling origami configuration of shape memory polymer was fabricated using 3D printing technology, followed by the execution of mechanical experiments, and the finite element analysis results were juxtaposed with experimental data to elucidate the mechanism. Then, the analysis of the flow field characteristics of the Kresling origami structure includes examination of the drag force properties of both single cell and array structures. The comparison shows that array structures offer better flow resistance than single-cell configurations. Additionally, the impact of the ventilation mechanism and double-layer structure on the drag force is investigated. Results indicate that Kresling origami structures exhibit varying drag force properties depending on folding states and wind direction, enabling efficient airflow regulation. The integration of non-reciprocal structures with double-layer Kresling origami is examined, demonstrating the potential of origami structures in intelligent ventilation, offering valuable insights for their application in fluid mechanics. [ABSTRACT FROM AUTHOR]

This research leverages resolved large eddy simulation to comprehensively explore the profound influence of yaw angle on the wake dynamics of tandem square cylinders. A rigorous grid sensitivity analysis substantiates the fidelity of the computational mesh, thereby guaranteeing the reliability and accuracy of the simulations. The findings reveal that the yaw angle exerts a significant and intricate impact on the aerodynamic coefficients of the cylinders, highlighting a nuanced interplay between drag and lift forces. Specifically, the upstream cylinder exhibits elevated mean drag coefficients, a trend that diminishes progressively with increasing yaw angles. In contrast, the mean lift coefficient of the downstream cylinder increases with rising yaw angle, while that of the upstream cylinder initially decreases until a critical threshold is reached, beyond which it subsequently ascends. Through meticulous analyses of the flow field and modal characteristics, including proper orthogonal decomposition, the study elucidates that an escalation in yaw angle induces wake deflection, thereby mitigating wake-induced interactions on the downstream cylinder and amplifying the yaw effect. These insights, garnered through a combination of computational and analytical methodologies, provide a deeper understanding of the fluid dynamics governing the wake dynamics of tandem square cylinders under yawed conditions. • LES reveals nuanced yaw effects on tandem square cylinders, advancing aerodynamic insights. • Yaw angle's impact on drag and lift coefficients offers pivotal benchmarks for engineering. • POD-based insights explain yaw-induced wake deflection and interaction mitigation in tandem setups. [ABSTRACT FROM AUTHOR]

A theoretical investigation of the problem of thermocapillary motion of a spheroidal drop freely suspended in a viscous incompressible fluid with a prescribed constant temperature gradient along the axis of revolution of the drop is presented under the steady limit of vanishing Péclet and Reynolds numbers. The flow fields in the exterior and interior of the drop are governed by the Stokes equations whereas the temperature fields in both the regions are governed by Laplace's equation. The general solution for prolate and oblate spheroidal drops can be expressed as infinite series in the forms of separation of variables for temperature distribution and of semi-separation of variables for the stream function. The leading order coefficients can be obtained using suitable boundary conditions which can be numerical values obtained from boundary collocation method or explicit formulas derived analytically. The thermocapillary migration velocity of the spheroidal drop is evaluated numerically with adequate convergence behavior for various values of the internal-to-external viscosity ratio, axial-to-radial aspect ratio and the relative thermal conductivity of the drop. It is revealed that the normalized thermocapillary migration velocity increases with the aspect ratio except for the case when the relative thermal conductivity of the drop is small and the internal-to-external viscosity ratio is relatively large. It is further observed that the normalized migration velocity approaches zero for an oblate spheroidal drop with the aspect ratio approaching zero and can be much greater than unity for a prolate spheroidal drop with a large value of the aspect ratio. [Display omitted] • The normalized thermocapillary migration velocity U / U 0 increases with the aspect ratio a / b. • Except for the case when the relative thermal conductivity k of the drop is small and the internal-to-external viscosity ratio η is relatively large. • The normalized thermocapillary migration velocity U / U 0 of prolate spheroidal drop exceeds unity whereas it remains within unity for oblate spheroidal drop. • The value of U / U 0 approaches zero for an oblate spheroidal drop with a / b → 0 and can be much greater than unity for a prolate spheroidal drop with a large value of a / b. [ABSTRACT FROM AUTHOR]

[Display omitted] • Attaching an inlet nozzle to the diffuser does not significantly improve turbine output power. • The 2D approach can accurately sort diffuser configurations based on power coefficient and drag force in the same order as the 3D approach sorts. • Neglecting the change in dynamic pressure in 2D analysis can lead to misleading results. • The 2D approach can be used for the preliminary design stage of diffuser-augmented small-scale wind turbines, which could reduce the computational costs. • The 2D approach is suitable for comparative analysis but may not provide precise predictions of output power coefficients or drag force. • It's recommended to simulate the diffuser with a load during design and optimization processes. This paper presents a novel comparative study of six different diffuser configurations used with a small-scale wind turbine, analyzed through both 2D and 3D approaches. These diffuser configurations are divided into two categories: without inlet nozzles and with inlet nozzles. The 2D approach is adopted to assess the feasibility of using its results for comparative analysis between different configurations. Subsequently, the 2D approach could be employed in preliminary design stages before performing the 3D simulations, thereby the computational costs could be reduced. In the 3D approach, a small-scale wind turbine is tested with the six different diffuser configurations across various tip speed ratios. In the 2D approach, the turbine is modelled as a uniform actuator disk or a load with different load coefficient values. Both 2D and 3D developed models were validated against experimental data from the literature. The key parameters investigated include the air mass flow rate through the diffuser, the drag force acting on the diffuser, and the extracted power by the turbine or the load. The extracted power in the 2D approach is calculated using two equations: one neglects the change in the dynamic pressure across the load, while the other accounts for it. The primary finding of this study is that neglecting the change in the dynamic pressure in the 2D approach can lead to misleading results regarding the performance of diffuser-augmented small-scale wind turbines. Additionally, the 3D analysis indicates that attaching an inlet nozzle to the diffuser does not significantly enhance the turbine's output power, corroborating experimental findings from existing literature. Similar observations are noticed from the 2D approach when using the power equation that considers the total pressure change across the load instead of the static pressure change. The turbine's maximum power coefficient of approximately 40 % was obtained for the diffuser with a 10-mm-flat flange and it was less by about 1.9 % when attaching the inlet nozzle. [ABSTRACT FROM AUTHOR]

Volume-averaged flow equations model fluid systems with two or more interpenetrating phases, as used in various engineering and science applications. Each fluid obeys its own set of Navier–Stokes equations, and the interphase coupling occurs via mass conservation, drag forces, and a common pressure shared by all phases. Therefore, designing decoupling schemes to avoid costly monolithic solvers is a complex, yet very relevant task. In particular, it requires treating the pressure explicitly in a stable way. To accomplish that, this article presents an incremental pressure-correction method built upon the fact that the mean (volume-averaged) flow field is incompressible, even though each individual phase may have a non-solenoidal velocity. To completely and stably decouple the phase equations, the drag is made implicit–explicit (IMEX). Furthermore, by treating all nonlinear terms in a similar IMEX fashion, the new method completely eliminates the need for Newton or Picard iterations. At each time step, only linear advection–diffusion–reaction and Poisson subproblems need to be solved as building blocks for the multi-phase system. Unconditional temporal stability is rigorously proved for the method, i.e., no CFL conditions arise. The stability and first-order temporal accuracy of the scheme are confirmed via two-phase numerical examples using finite elements for the spatial discretisation. [ABSTRACT FROM AUTHOR]

The laser welding process is an important manufacturing technology for metallic materials. However, its application is often hindered by the occurrence of porosity defects. By far, an accurate prediction of the porosity defects and an insight into its formation mechanism are still challenging due to the highly nonlinear physics involved. In this paper, we propose a physics-informed deep learning (PIDL) framework by utilizing mechanistic modeling and experimental data to predict the porosity level during laser beam welding of aluminum alloys. With a proper selection of the physical variables (features) concerning the solidification, liquid metal flow, keyhole stability, and weld pool geometry, the PIDL model shows great superiority in predicting the porosity ratio, with a reduction of mean square error by 41 %, in comparison with the conventional DL model trained with welding parameters. Furthermore, the selected variables are fused into dimensionless features with explicit physical meanings to improve the interpretability and extendibility of the PIDL model. Based on a well-trained PIDL model, the hierarchical importance of the physical variables/procedures on the porosity formation is for the first time revealed with the help of the Shapley Additive Explanations analysis. The keyhole ratio is identified as the most influential factor in the porosity formation, followed by the downward flow-driven drag force, which offers a valuable guideline for process optimization and porosity minimization. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A drag model is established including Froude number and density ratio. • Increasing liquid velocity enhances bubble number and size with Froude number. • Transition of fluidization state occurs at a densimetric Froude number of 0.411. • Increasing liquid velocity reduces the interphase drag with Froude number. The degree of bed expansion in fluidized beds is influenced by the heterogeneous flow, which affects interphase momentum transfer, especially for particles with high density relative to the fluid, where gravity plays a significant role. To account for the effects of heterogeneity, a drag model is developed depending on the particle Reynolds number, the densimetric Froude number, and the ratio of solid to liquid density. The densimetric Froude number can evaluate the bed fluidization quality. The flow behavior of Geldart D particles in fluidized beds is simulated using the proposed densimetric Froude number-based drag model. This model demonstrates good agreement with the experimental data compared to the Gidaspow_blend, Koch_Hill, and Wen_Yu drag models. Additionally, the study concentrates on the non-uniformity induced by variations in liquid velocity and the transition from transitional to heterogeneous fluidization for the solid phase. A quantitative analysis is conducted on the flow patterns under different particle densimetric Froude numbers, as well as the relationship between interphase drag force, particle Reynolds number, and densimetric Froude number. As the liquid velocity increases, the number and size of liquid bubbles increase with the particle densimetric Froude number. At a densimetric Froude number of 0.411, the bed transitions from a transitional to a heterogeneous fluidization state. Moreover, as the liquid velocity increases, the interphase drag coefficient decreases with the increase of particle densimetric Froude number. The influence of solid volume fraction on drag force is greater than that of liquid–solid slip velocity, particle Reynolds number and densimetric Froude number. [ABSTRACT FROM AUTHOR]

[Display omitted] • The dynamic characteristics of bubble in Taylor-Couette reactor is investigated. • The movement mode of the bubble transitions is clarified. • The fitting formula of bubble trajectory in Taylor-Couette reactor is given. Taylor-Couette reactor is a potential equipment for enhancing mass transfer, heat transfer and reaction in the chemical field by modifying the gas–liquid flow behavior. In this paper, visual experimental measurements of bubble motion in the reactor were conducted using high-speed camera. Moreover, with the help of CFD and force analysis, the motion mechanism of bubble was also carried out in the reactor. The results show that in the range of rotational Re from 0 to 17410, bubbles in the annulus have three motion forms, namely free rise, spiral rise and banded motion. When rotational Re exceeds the critical value of 10446, the bubble motion is transformed into the banded motion, trapping bubbles between Taylor vortex pairs near the inner cylindrical. This transition occurs due to the equilibrium between buoyancy and axial drag forces. In addition, the equation of bubble motion in Taylor-Couette reactor is established. These provide a key reference for the research and development of high-efficiency absorption and reaction strengthening equipment. [ABSTRACT FROM AUTHOR]

This paper presents a parametric study of hydrofoils investigating various design configurations carried out with CFD. The purpose of the study is to assess the hydrodynamic performance enhancements achieved by incorporating different design parameters, including the addition of winglets, the variation of the strut angle, the addition of bulbs, and the free surface proximity. It is shown that greater changes in lift and drag forces are found for the winglet design and the influence of the free surface. For the former, upward or downward winglets with high cant angle give the best overall performance in terms of CL/CD ratio. For the latter, an optimum CL/CD ratio is found for relative free surface heights between 2 and 3. The addition of a bulb is necessary from the structural and propulsion points of view and reduces the CL/CD ratio, but different bulbs have minimal impact on hydrodynamic performance. The variation in the strut angle has an impact on the drag coefficient for values larger than 30 degrees due to the increase in virtual thickness. These results offer valuable insight into the effects of these design parameters on the hydrofoil performance, providing potential avenues for optimizing hydrofoil efficiency. • A parametric 3-D CFD study is conducted to investigate performance of several hydrofoil elements. • CFD verification and validation analyses confirm the accuracy for hydrofoil analysis. • Winglet design and free surface operation significantly impact hydrofoil performance. • Bulb and strut angles minimally affect hydrodynamic performance. [ABSTRACT FROM AUTHOR]

Foam concrete encounters a fundamental challenge in balancing lightweight and high strength. Pore optimization is the key to address this problem. This study starts with rheology control to optimize the pore structure of foam concretes, thereby designing high-performance foam concrete (HPFC). X-ray computed tomography was employed to explore the relationship between rheology and pore characteristics, revealing the corresponding control mechanisms. The findings indicated that rheological parameters, particularly viscosity, significantly influenced pore size, uniformity, sphericity, fractal dimension and connectivity. Therefore, there was an optimal viscosity range (1.30 ± 0.15 Pa·s) for achieving the desirable pore structure. Mechanical analysis demonstrated that the viscosity could impact the balance of the added foams under dynamic and static conditions via drag force, resulting in changes to the pore structure. After pore optimization, the HPFCs exhibited high compressive strength (2–3 times higher than normal foam concrete at an equal density) and excellent durability comparable to high-performance concrete. • A design concept and method of an HPFC in terms of terminology and definition were proposed. • The relationship between the rheology and pore structure of HPFC was clarified. • The pore structure of HPFC was successfully optimized by the rheology control. • A HPFC product with high strength and excellent durability was developed successfully. [ABSTRACT FROM AUTHOR]

A new fluid–solid coupled numerical approach is developed by combining the CFD (Computational Fluid Dynamics) − DEM (discrete element method) with the pore network model (PNM) to simulate the erosion of the soil-rock mixture. The pore network with pore and pore pipes is constructed based on the particles and updated regularly. A relationship equation is derived between the permeability scalar for micro-scaled pore pipe and the anisotropic permeability tensor for macro-scaled fluid element. By the Delaunay-PorePy-PFC3D program framework, the erosion process of the soil-rock mixture with different fine contents (FCs) is simulated. The results show that the PNM-CFD-DEM model can meet the computational accuracy for simulating the rule-arranged uniform particles. The duration of the erosion stage is different for specimens with different FCs. The PNM-CFD-DEM model can reproduce the particle erosion paths in different specimens, as well as the adjustment of the pore network between their coarse particles. The preferential drag forces in the discrete portion take into account the pore network formed by the state of the particle buildup within each fluid element. [ABSTRACT FROM AUTHOR]

Ensuring the safety integrity of the core catcher system during a hypothetical core disruptive accident (CDA) in a sodium fast reactor (SFR) is crucial, particularly regarding the formation of the debris bed. This study presents a novel, fully explicit Discrete Element Method (DEM) coupled with Moving Particle Hydrodynamics (MPH), accelerated on a graphics processing unit (GPU), to calculate debris bed formation with various particle sizes. The DEM approach is applied to the solid phase, while the liquid phase is calculated using the MPH method. The DEM-MPH method is explicitly updated to avoid significant differences in time steps and to efficiently accelerate calculations on the GPU. For validation, a fundamental dam break simulation with tiny particle sizes (0.5 mm) was conducted. The simulation results show good agreement with experimental data in terms of the angle of repose and spread length. Additionally, the GPU-accelerated calculations demonstrated a calculation efficiency of several hundred times improvement compared to a single CPU. The DEM-MPH method was also compared to a previous experiment conducted by Sun Yat-Sen University, demonstrating the capability of handling almost 10 million particles. The results indicate that particle size significantly impacts debris bed formation. As particle size decreases, the debris bed shape becomes flatter due to the more significant convection within the liquid pool and the drag force between the solid phase and the liquid. All calculations showed agreement with experimental results regarding debris bed height. Overall, the present DEM-MPH method shows great potential for understanding debris bed formation, which is indispensable for ensuring SFR safety. • A fully explicit DEM-MPH method has been developed. • GPU acceleration enhances calculation efficiency, enabling simulations with up to 10 million particles. • Debris bed formation experiments were analyzed using the DEM-MPH method, revealing that particle size significantly influences sedimentation behavior. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mixing and segregation behaviors of binary are simulated by CFD-DEM. • The cylinder-shaped particles are constructed with a super-quadric model. • Particle shape does show remarkable influence on the quality of mixing and segregation. • Disc- or rod-like particles are more likely to generate heterogeneous torque. • The increase of density ratio can decrease the impact of particle shape on segregation. In this paper, the Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) is applied to investigate the mixing and segregation of binary cylinders with different densities in a three-dimensional liquid–solid fluidized bed. The column-shape particles are constructed with a super-quadric model. The simulation results are in good agreement with the previous experimental data. The influences of aspect ratio and density ratio of binary particles on the mixing quality and final segregation extent are examined. Simulation results show that light particles are inclined to occupy at the top of the granular bed, whereas heavy ones concentrate in the bottom. As particle aspect ratio deviates from unity, i.e. disc-like or rod-like particles, the mixing index is increased and segregation degree is decreased. Particle translation is the main movement mode, however, disc- or rod-like particles are more easily to rotate and need more energy to be driven, comparing with approximately spherical particles. The force analysis in terms of the contact force and drag force indicates that particle shape influences collision probability, resulting in greater contact forces in terms of the disc-like and rod-like particles. Compared to disc-like and rod-like particles, approximately spherical particles experience the least drag force, thereby inhibiting mixing between binary particles. The particle orientation of disc-like and rod-like particles is inclined to the vertical direction in the fluidized state. Furthermore, particle dispersion coefficients are in the range of 10-3 to 10-2 m2/s, whose vertical direction is one order of magnitude greater than the horizontal directions. Smaller density ratios lead to larger particle dispersion coefficients. [ABSTRACT FROM AUTHOR]

• Numerical Study on the ERVC system,China. • Investigating the types of fins, three fin structures (Longitudinal fin, Rectangular fin, Cylindrical fins) • The CHF effect of cylindrical fin is better than rectangular fin and longitudinal fin. • Wall boiling model. • Two phase flow. Under the serious accident of core melting, in-vessel retention (IVR) can end the accident process inside the pressure vessel as an emergency strategy. The ERVC can remove the residual heat of the core. The paper utilizes the method of enhanced heat transfer to improve CHF threshold. In this paper, according to investigating the types of fins, three fin structures (Longitudinal fin, Rectangular fin, Cylindrical fins) are selected and placed on the thermal insulation layer, which change the internal structure of the flow channel to play the role of turbulence disturbance. For the multi-phase flow model, a boiling model (RPI model) is used, considering the momentum exchange between the two phases, like drag force, virtual mass force, and wall lubrication force, as well as interphase mass transfer and heat transfer. The mathematical physical model is verified for the slicing experiment of ULPU, and the calculated result is compared with experimental physical values, as well as the error is within acceptable ranges, which are in good agreement. The calculations show that the CHF effect of cylindrical fin is better than rectangular fin and longitudinal fin, since that the turbulence intensity of around cylindrical fin is stronger than rectangular fin and longitudinal fin. For the same fin, when the fins spacing are smaller and fins height are between 40–60 mm, the cylindrical fin geometry has better cooling effect on the core and the residual heat removing. The enhanced heat transfer effect of cylindrical fins can be improved by 21 %.The numerical simulation calculation results can provide certain reference for engineering design. [ABSTRACT FROM AUTHOR]

CO 2 bubbles flow in the anode flow channel is an important issue in the commercialization process of direct methanol fuel cells (DMFC). A T-channel model is built in COMSOL using the phase field method to investigate the CO 2 bubbles flow at the anode side of the DMFC. The factors and mechanisms of single bubble detachment are discussed by analyzing the methanol inlet velocity (U l), CO 2 inlet velocity (U g), contact angle of the diffusion layer, and the Weber number during bubble detachment. The research findings indicate that increasing the liquid flow rate leads to the generation of smaller bubbles that detach more rapidly due to the increases of drag force (F D) and the shear-life force (F SL) to overcome the surface tension on the bubble. The CO 2 inlet velocity can promote the bubble detachment due to the increase in F SL , but also leads to a larger detachment diameter. Compared to hydrophobic surfaces, hydrophilic surfaces are more conducive to bubble detachment and removal. In all case We (Weber number) is significantly less than 0.6, indicating that liquid momentum dominated the bubble detachment process. Once the ratio of the gas momentum to the liquid one is greater than 1, the bubble is hard to detach. The contour map of bubble flow patterns and the bubble detachment diameters distribute with the ratio of U g / U l can further indicate that the bubble detachment is connected with the ratio of U g / U l closely, which will have guiding significance for the selection of inlet velocity of DMFC. • A 2D T-channel two-phase model of DMFC is presented. • Bubble behaviors are investigated by simulation using the phase field method. • A contour plot of the detached diameter of a bubble is created. • The forces on the bubble during detachment are quantitatively analyzed. • Optimal flow conditions to promote bubble detachment were obtained. [ABSTRACT FROM AUTHOR]

This paper presents an analytical model for the propagation of a toroidal interplanetary magnetic cloud from the vicinity of the Sun to Earth's orbit. This model is applied to the May 12–15, 1997 event for calculations of cloud's acceleration and velocity using a three forces approximation in driving the magnetic cloud's dynamics: the diamagnetic push away from the stronger magnetic field region near the Sun, a drag force due to the ambient solar wind, and the Sun's gravity pull. From the minimization of the difference between the calculated versus observed transit time of the magnetic cloud, we determine free parameters of our model and identify the solar source on May 12 at 5:03 UT. In situ measurements near Earth's orbit done before May 12 set the values of the ambient interplanetary magnetic field, as well as of the ambient solar wind through which the magnetic cloud traveled. The observed temperature and density inside the magnetic cloud at Earth's orbit determine the corresponding inner values during the magnetic cloud's propagation. The coefficient of the drag force is one of free parameters in the model. • Analytical model for a toroidal magnetic cloud propagation is presented. • The model is used for the interpretation of May 12–15, 1997 event. • The difference between model and observed transit time is about 1 h. [ABSTRACT FROM AUTHOR]

Anthropogenic and natural weathering processes have produced submicron microplastics (MPs), an emerging contaminant. Due to small size, the treatment of submicron plastics particles by membrane processes requires small cutoff membranes, which necessitates great pressure gradient and suffers from clogging. The present study aims to develop an electrophoretic separation system for the separation of negatively charged submicron plastics particles from water. An electric field was supplied to produce an electrostatic force to counter the drag force in the permeation stream, thereby, preventing submicron plastics particles from entering the permeate. The critical electric field (E c) for complete particles removal was estimated based on the dilute-to-influent flow rate ratio (q d), zeta potential, and size of submicron plastics particles. The result showed that at steady-state, particle removal could reach 99 % at E > E c at q d = 0.5. The distribution of plastics particles during electrophoretic separation was analyzed considering electrophoresis and particle deposition. The particle removal efficiency can be modelled by hydraulic condition and critical electric field. Finally, the engineering aspects such as long-term operation, electrode degradation and influence of coexisted constituents were evaluated. The operation cost of electrophoretic separation was calculated to be USD 0.48/m3, which is cost-effective at small scales compared to conventional membrane processes. [Display omitted] • Electrophoretic separation successfully removes PS nanoplastics from water. • Zeta potential, cell geometry, and hydraulics control the critical electric field. • Electric field greater than critical value completely removes PS nanoplastics. • A model based on force field and mass balance well predicts removal efficiency. • Specific energy consumption is 5.0 kWh /m3 at dilute flow fraction of 0.5. [ABSTRACT FROM AUTHOR]

Internal Wave (IW) is a kind of wave that occurs below the sea surface. Compared with surface wave, the force applied to underwater structures is more destructive. This paper experimentally investigates the interaction process between Internal Solitary Wave (ISW) and submerged body, and proposes two new dimensionless parameters and uses these two dimensionless parameters to analyze the force of the submerged body with different ISW amplitude and submerged depth. At the same time, these two dimensionless parameters can be used to classify the lateral force and vertical force of the submerged body. Finally, the influence of velocity and acceleration field on the force of the submerged body is considered. The results show that the extreme value will increase with the increase of ISW amplitude. The variation of horizontal force under d 0 ∗ condition is completely different from that of d + ∗ and d − ∗. The dimensionless number L ∗ affects the action time, and the dimensionless number d ∗ affects the change rule of vertical force. The horizontal inertial force plays a dominant role in the horizontal force. When d ∗ = − 1.17 , the inertial force plays a dominant role in the vertical force. When d ∗ > 0 , the drag force plays a dominant role in the vertical force. • The laboratory experiments of ISW and slender submerged body were carried out in a stratified fluid tank. The stratified fluid tank can generate ISW with different amplitudes, and the submerged body can change different diving depths, which provides convenience for parametric classification analysis. • According to the logical analysis, two new dimensionless parameters are proposed. The analysis in this paper is based on the above dimensionless parameters, and the influence of ISW amplitude and diving depth on the force of the submerged body is discussed in detail. • It is found that the interaction time between ISW and the submerged body is a quantity related to L ∗. The vertical force curve of ISW interacting with the submerged body is related to d ∗ , and different cases are classified according to d ∗. In addition, the effects of inertia force and drag force are discussed. [ABSTRACT FROM AUTHOR]

• A pilot scale jet-flow HSM was applied to accelerate drawdown dispersion process. • It can easily complete drawdown dispersion in high solid content up to 40 %. • The mechanism of drawdown dispersion of light floating particles was revealed. • Mathematical models for estimation of the N jd and P jd were established. The jet-flow high shear mixer (HSM) was applied to accelerate the drawdown dispersion process of light floating particles. It can easily complete drawdown dispersion operations in high solid content up to 40%. The process analysis on drawdown dispersion was performed by high-speed camera and CFD simulation. The critical speed N jd , critical power consumption P jd , and particle dispersion uniformity σ 2 were experimentally measured. The central vortex, turbulent fluctuation and drag force are main driving force in the first stage, while the forced suction and spraying of rotor–stator shear head are main driving force in the second stage. Increasing rotor speed can enhance the mixing efficiency. Within the range of 40 %, the higher the solid content, the more energy-efficient the jet-flow high shear mixer. The N jd and P jd were significantly reduced when using downforce rotor, and stator with a fully open bottom, while the dispersion uniformity was increased. Adopting an eccentric arrangement can reduce the N jd and P jd , but it is not recommended as it can lead to uneven particle distribution. Dimensionless correlations were established to estimate the N jd and P jd of jet-flow high shear mixer, which can provide effective guidance for its practical application. [ABSTRACT FROM AUTHOR]

The flow forces on step-pool units are important to understand the physical processes and flow resistance partitioning in step-pool channels, and build the basis for better prediction of channel evolution and more advanced design of artificial step-pool system. However, the flow forces acting on step-pool units are understudied and poorly understood. To fill this knowledge gap, we applied the approach combining physical experiment and computational fluid dynamics simulation to a step-pool unit made of natural grains at six flow conditions. The topography of the step-pool unit was split into topography components (TCs) covering the entire unit length with the same width. The flow forces from both pressure and shear stress in XYZ directions were examined for the TCs. The results illustrate significant transverse variability of the flow forces from both the shear stress and pressure at all the three directions. The flow forces in both X and Y directions are closely related to the flow structures and morphology in the unit. The ratios between skin and form drag have large variations at low flows while show a relatively limited range of 0.05–0.1 at high flows, suggesting a small proportion occupied by the skin resistance in the total flow resistance in the step-pool channel. The drag and lift coefficient generally increase with discharge and the drag coefficient of the unit is around 0.3 at high flows, which can be used in evaluating the stability of the step-pool units in a sequence. • Flow forces from shear stress and pressure in a step-pool unit were simulated. • All of the flow forces in XYZ directions show significant transverse variability. • Ratios between skin and form drag on unit-long bed range in 0.05–0.1 at high flows. • The drag coefficient of the step-pool unit is around 0.3 at high flows. [ABSTRACT FROM AUTHOR]

Biomolecules are indispensable in the life activities and metabolism of various organisms, and their highly sensitive detection is of great significance for disease diagnosis and food safety. Due to the complexity of the matrix and the low concentration of the target, separation and enrichment of biomolecules prior to detection are necessary and time-consuming. Herein, a novel approach combining in-capillary magnetic separation and enrichment with laser-induced fluorescence detection method was proposed for qualitative and quantitative analysis of biomolecules. Two different sequence aptamers modified with magnetic nanoparticles and labeled with fluorescence were used as capture probes and signal probes to form sandwich structures with target molecules for detection. Under the combined influence of magnetic field force and fluid drag force, the integration of separation, enrichment and on-line detection were finished within 5 min. Under optimal conditions, the developed method provided a low limit of detection as 2.7 fmol/L, 0.57 nmol/L, 3 CFU/mL for DNA, thrombin and Staphylococcus aureus , respectively. This proposed method offers a promising platform for the sensitive and rapid determination of biomolecules. It holds significant potential for future applications in fields of environmental and biochemical analysis. • Fluorescently labeled aptamer and aptamer-coated magnetic nanoparticles forming a bio-target sandwich structure. • In-capillary magnetic separation, enrichment and on-line laser-induced fluorescence detection. • In-capillary separation, enrichment and on-line detection finish within 5 min. • Multi-applications in sensitive analysis of DNA, protein and bacteria. [ABSTRACT FROM AUTHOR]