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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]

To improve the aerodynamic efficiency of the aircraft, the article focuses on optimizing the L/D ratio through postponement of flow separation. Elevating the L/D ratio leads to diminished drag and delays stall occurrence at high angles of attack (α). The wing geometry adopts NACA 6-digit airfoils, specifically NACA 63418 and NACA 63415. Various aerodynamic devices are explored for their ability to defer flow separation, with passive aerodynamic devices being the prevalent choice. The primary goal of the research is to integrate rotational thin wire elements into the aerodynamic components of the wing, aiming to diminish drag, amplify lift, and enhance overall aerodynamic performance. The analysis spans a range of α, from 0° to 20°. The study encompasses two scenarios: one without the incorporation of aerodynamic devices and the other with their implementation. Comparative analyses of increases in CL and reductions in CD, with notable improvements observed at a 15o angle of attack, 28.47% increase in CL and 15.07% decrease in CD. Furthermore, the improved performance in the CL/CD, which increases substantially in stall conditions, thereby demonstrating the potential of these aerodynamic modifications to enhance overall aircraft performance. [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]

This study investigates pressure gradient dynamics within a porous medium in the context of two-phase fluid flow, specifically water and sand particle interactions. Using experimental data, we refine pressure correction coefficients within a numerical solution framework, employing the Semi-Implicit Method for the Pressure-linked Equations algorithm. Our findings highlight the relative nature of pressure gradient phenomena, with particle size and volume fraction emerging as crucial determinants. Graphical representations reveal a clear trend: an increase in volume fraction, up to 40%, across varying Reynolds Numbers, leads to a transition towards non-Newtonian behavior in the two-phase fluid system. Unlike the linear pressure gradient seen in single-phase fluid flow, the interplay between liquid and solid phases, along with drag forces, imparts a distinctly nonlinear trajectory to the pressure gradient in two-phase fluid flow scenarios. As the two-phase flow enters a porous medium, numerous factors come into play, resulting in a pressure drop. These factors include changes in cross-sectional geometry, alterations in boundary layer dynamics, and ensuing momentum fluctuations. Interestingly, an increase in porosity percentage inversely correlates with pressure gradient, resulting in reduced pressure gradient with higher porosity levels. [ABSTRACT FROM AUTHOR]

Savonius, a type of vertical-axis wind turbine, is a small-scale energy conversion device suitable for low wind speeds, such as those characteristic of Indonesian wind speeds, yet has low efficiency. Savonius is a drag-type turbine. Drag force on the surface is affected by roughness or wavyness. The purpose of this study is to analyze the impact of applying wavy (zigzag) variations to the concave surface of Savonius blades on their performance. This was achieved by the use of 3D computational fluid dynamics simulation at TSR 0.6 with a velocity inlet of 5 m/s. The model was semicircular, zigzag on the concave surface on semicircular with t = 0.75, t = 0.25, and t = 1 mm. The result of this study's CRDR maximum is 1,817 at the zigzag model with t = 1 and CRDR avrg =1.24. The average drag coefficient increased by 14 percent compared to the conventional semicircular rotor. The maximum Cp value is also found at t = 1 mm, which is 0.315. The power coefficient increased by 29 percent compared to the conventional semicircular rotor. The total pressure on the blade shows the highest model with t = 1 mm at the same angle of attack (a = 30). Zigzag on the concave surface affects blade pressure, which improves the performance of the Savonius rotor. [ABSTRACT FROM AUTHOR]

The bullet shape is critical in efficient bullet design because it affects the lift and drag forces. This paper proposes a new bullet shape with a logarithmic curve and analyzes the lift and drag coefficients of bullets with different curves under different angles of attack. The results are compared with a bullet whose shape is described by the power law curve. Fluent simulations demonstrate that the optimal power exponent values are 0.65, 0.6, and 0.65 for the bullet with the power law curve and 1.3, 1, and 1 for the bullet with the logarithmic curve at 0°, 30°, and 40° angles of attack, respectively. At a 0° angle of attack, the lift coefficient of the logarithmic curve is the largest. The lift force of the bullet with the logarithmic curve is 129.4% higher than that with the von Karman curve. The drag coefficient is the largest for the bullet with the rectilinear curve; it is 1.30% larger than that of the bullet with the logarithmic curve. At 30° and 40° angles of attack, the lift coefficient of the bullet with the power law curve is larger. The difference in the lift coefficients between the two angles of attack is 18.47%. The bullet's drag coefficient is the largest for the logarithmic curve, and the difference in the drag coefficients between the two angles of attack is 18.59%. [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]

Imitating Dolphin fish-like movement is productive method for enhancing their hydrodynamic capabilities. This work aims to analyze and understand the oscillations of tail fluke of Dolphin, which can be used as a propulsive mechanism for underwater fish robots and vehicles. The objective of the work is to achieve the desired oscillating amplitude by simulating the NACA 0012 profile using computational models and Set up the swimming movement of the dolphin, imitating a fish like model. Computational techniques were employed to examine the propulsive capabilities of the oscillating hydrofoil, inspired by the dolphin's biological propulsion. The evolutionary of fluid pattern in the field surrounding both Dolphin fish model and the NACA0012 hydrofoil, from initial motion to cruising, was established, and the hydrodynamic impact was subsequently studied. An user-defined function (UDF) was developed to create a dynamic mesh interface with CFD code ANSYS FLUENT for establishing the oscillations of Dolphin tail across the flow field. Influencing hydrodynamic coefficients such as lift and drag coefficients at different frequencies were also obtained. The findings shown that when the acceleration of the Dolphin fish model increases, the time averaged drag force coefficient drops because The wake field's vortex disperses to have some beneficial effects and pressure of water surrounding the fish head intensifies to produce a large resistance force. Simulation results show a 98% agreement at lower frequency and speed levels but a 5% deviation at higher frequency and speed due to turbulence effects in both models. It was established that the vortex superposition enhances the Dolphin fish like model rather than lowering its positive impacts. The Strouhal number, which is obtained by the fluid field's evolution rule, can be linked to the Kármán vortex street span with reverse. [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]

Natural or human-induced intra-annual variation of river discharge alters estuarine hydrological regimes and further affects habitat conditions for saltmarsh vegetation, particularly at the river mouth bar. In this study, numerical experiments were performed in Delft3D to simulate the evolution of a schematized river mouth bar under prototypical unsteady river discharge scenarios. The simulated hydrodynamic and morphodynamic changes were used to drive a vegetation dynamics model developed based on Spartina alterniflora in real time to model the resultant vegetation responses throughout the plant life history. Our results show that the imposed seasonal high flow can create more potential suitable habitat for the vegetation expansion and at the same time, cause marsh erosion through flood-induced drag force and substrate erosion. The overall effect of the trade-off between expansion and erosion depends on the timing, magnitude and duration of the high flow as well as its carried sediment concentration, leading to three vegetation response regimes, namely, minimal impact with small flood, erosion with big flood and low sediment supply, and expansion with big flood and high sediment supply. Besides, the timing of the high flow determines whether the vegetation has enough time to occupy the newly created subaerial area after the high flow and thereby affects the overall saltmarsh extent. The proposed vegetation response regimes are verified in principle in real cases such as Yellow River Estuary, Wax Lake Delta and Yangtze River Estuary. Our findings can help inform water diversion projects in river deltas to restore coastal wetlands in terms of suitable sediment supply and timing, etc. [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]

The continuous demand and fuel depletion in the automobile industries cause a reduction in fuel consumption, especially in a car which is a classic problem to focus on vehicle body design. The formation of drag force in the car body demands tractive force and significantly affects the engine performance and fuel consumption rate which is not advisable for enhancing aerodynamic efficiency. This paper discusses the methodology to reduce the fuel consumption rate in hatchback cars using a 'basebleed method'. The hatchback car model with and without basebleed is numerically simulated for the various speed to study the aerodynamic coefficients. The numerical simulation is performed with the k-ε turbulence model for predicting the wake region of both car models with and without basebleed. The numerical study witnessed the hatchback car model with basebleed arrived 6% reduction in the coefficient of drag (CD) compared to without basebleed, which results in a reduction of fuel consumption rate of up to 4.33 %. The research evidence that the stability of the car is not affected while using this basebleed drag reduction method and it is studied from the resultant parameters such as coefficient of lift (CL) and coefficient of side force (CS) and for the varying yaw angle (φ). Further, the research recommends the integration of basebleed at the underbody structure in Hatchback cars to improve the engine fuel consumption without affecting its stability. [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]

As a widely used taut-wire mooring system for deepwater platforms, the Vertically Loaded Anchor (VLA) has better performance in bearing capacity, angle adaptability, and deepwater installation than other systems. However, the installation process of the VLA and its motion characteristics are significantly impacted by multi-layered seabed soil. In this paper, the coupled Eulerian-Lagrangian (CEL) large deformation finite element analysis method has been applied to analyse the continuous penetration of a VLA in nonuniform clay with an interbedded stiff layer. A detailed parametric study has been carried out to explore the trajectory, drag angle, movement direction and drag force of the VLA in layered clay with different embedded depths, thicknesses and undrained shear strength of the stiff layer. The CEL numerical analysis results have been validated by comparison with the analytical solutions from the inverse catenary equation. Excellent agreement has been obtained between the results from the CEL analyses and the analytical solutions. The stiff layer leads to concave and convex shapes on the trend lines of the movement direction angle and drag forces, respectively. The embedded depth of the stiff layer determines where the concave and convex shapes appear on the trend lines, while the thickness affects the sizes of the openings of the shapes. The most decisive parameter, an abrupt variation in the undrained shear strength, causes predominant rotation at the interface of layered clay. It diminishes the final embedment depth and ultimate stable drag force, meaning that the bearing capacity of the VLA severely declined in layered clay. [ABSTRACT FROM AUTHOR]

The aerodynamic performance of four train models with different windshield configurations (i.e., internal and/or external) in three train marshalling modes (i.e., 3, 6 and 8-car groups) was numerically investigated in this study. The train's airflow characteristics at Re=2.25×106 were determined using the shear stress transport (SST) k-ω turbulence model. The results were validated by comparing the pressure distributions and drag forces on the streamlined heads with experimental data. The difference in windshield configuration and train length has a substantial influence on the train's flow field and surface pressure distribution. For the trains with internal windshields, due to non-uniform geometry, the flow is separated and vortices are formed at the windshield area. The boundary layer profile increases with the increased train length, and its thickness varies with windshield configurations. Asymmetric vortices are formed in the wake at a distance close to the tail car's nose, except for trains with external windshields. The reduction of the flow velocity as the train length increases causes a reduction of the low pressure near the tail car's streamline transition, thus causing a decrease in the tail car's drag and lift forces. Consequently, for trains with external windshields, the head car's drag increases, whereas the total train drag reduces significantly as the train length increases. Therefore, employing external windshields in all the inter-carriage gap sections, irrespective of the train length, demonstrates a good ability to reduce future train's aerodynamic drag. [ABSTRACT FROM AUTHOR]

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Background. For effective magneto-abrasive machining (MAM) of complex-shaped parts, comprehensive information is needed on the processes that occur when the magneto-abrasive tool (MAT) contacts with the surfaces being machined. Effective magneto-abrasive machining occurs in the presence of sufficient values of the normal and tangential components of the interaction forces between the MAT and the machined surfaces and the powder mixing during machining. Previously carried out analytical studies of dynamic parameters did not take into account the real conditions of the interaction of grains and their groups with machined surfaces. Objective. Complex analysis of the processes that occur during magneto-abrasive machining of parts made from different types of materials, based on the results of the study of the friction forces between the magneto-abrasive tool and the surface being machined and the drag forces during the movement of parts in the working zone of the machine. Methods. To achieve the set goal, the forces acting on the samples during their magneto-abrasive machining were measured with subsequent analytical analysis. Results. The complex analysis of the processes occurring during MAM in conditions of the annular working zone with large working gaps of parts made of various materials was carried out based on the results of the study of the friction and drag forces that occur when the part moves relative to the magneto-abrasive tool. Conclusions. It has been determined that when machining non-magnetic samples at the constant value of the magnetic field in the working zone, the specific drag forces are practically independent of the shape of the used powder. According to the analytical representation of the friction and drag forces, their ratio between their specific values was calculated. By the nature of the change in this ratio, it was found that it decreases with an increase in the velocity of samples movement along the working zone, and with an increase in the angular velocity of rotation of the samples around its axis, this value increases in the studied velocity range. It has been determined that at the velocity of movement along the working zone of 2.2 m/s, there is a slight increase in the ratio between the specific forces of friction and drag, which is associated with the action of ponderomotive forces that appear near the surface of the machined parts and lead to an increase in local magnetic forces in these zones. [ABSTRACT FROM AUTHOR]

The study of a chemically reacting fluid in a vertical micro-channel limited to an applied transverse magnetic field that has fully developed steady natural convection flow under the impact of internal heat generation or absorption effects is the focus of this research. The governing equations are solved in dimensionless form using the homotopy perturbation method, HPM. Temperature, velocity, volume flow rate, and frictional drag force fundamental flow attributes are investigated as a function of controlling parameters such as heat generating or absorbing parameters, chemical reaction parameter, rarefaction parameter, fluid-wall interaction parameter and wall-ambient temperature difference ratio. The results are thoroughly analyzed and graphically depicted in a variety of plots. It is worth noting that raising the chemical reaction and rarefaction parameters increases fluid flow and volume flow rate, respectively. Furthermore, the action of heat absorption is observed to suppress fluid flow whereas heat generation establishes the opposite condition. Additionally, numerical data was generated and tabulated to compare the findings of this study to those of Jha et al. (2014) when the chemical reactant and heat generating/absorbing parameters were neglected, and an excellent agreement was discovered. [ABSTRACT FROM AUTHOR]

Heat transfer improvement using electro-magneto hydrodynamics is a technique that can result in significant heat exchanger reduction as well as "on-demand" heat transfer. Electrohydrodynamic (EHD) is a multidisciplinary science that studies how fluids interact with electric fields or charges. It has been found applications in many areas such as EHD pump, EHD enhanced heat transfer, microelectromechanical systems (MEMS) and other industrial processes. MHD offers a broad array of applications for researchers in astrophysics, planetary magnetic fields, generators, flow meters, metallurgy, metal dispersion (granulation), ship propulsion, crystal development, magnetic filtration, and fusion reactors. Investigation of the mass and heat transfer properties of hybrid nanofluid Transformer o i l + T i O 2 + F e 3 O 4 in three dimensions is considered. In this research, cumulative effects of magnetic and electric hydrodynamic are examined between two rotating plates in viscous hybrid nanofluid. To generate the hybrid nanofluid, transformer oil is utilized as a base fluid in the nanoparticles Ti O 2 and F e 3 O 4. Using a similarity approach, the flow model in the form of PDEs is reduced to a system of dimensionless ODEs. The obtained equations are solved by using a shooting (bvp4c) method to attain a numeric solution. Reynolds number, rotational factors and effects of magnetic and electric properties in hydrodynamics have all been researched and argued about thermal efficiency, drag force, and mass flux. Numerical data of Nusselt number, Sherwood number, and drag forces are calculated. By minimizing the influence of physical constraints, the hybrid nanofluid enhances heat transfer rate and mass transport. [ABSTRACT FROM AUTHOR]

• The aerodynamics of a half-span delta wing are studied using wind tunnel experiments at subsonic flow regime. • The lift on the delta wing is generated close to the leading edge for the focus range of the incidence angles. • Locations of the additional lift and the drag forces of the delta wing is identified based on the experimental results. Low-speed wind tunnel experiments are conducted to study the aerodynamic performance of a half-span delta wing with 45° leading-edge sweep at subsonic flow regime. The experiments are carried out at a Reynolds number of 8.37 × 105, a free-stream Mach number of 0.1 and angles of attack up to 25°, in steps of 5°. The test model was designed with thirty-two pressure taps fixed on its surfaces (sixteen on each side). Multi-tube manometers were connected to these taps using long tubes to enable recording the pressure readings. Surface pressure distributions and aerodynamic characteristics were calculated at different span-wise locations along the non-dimensional chord-wise distance. Results exhibited that most lift on the studied wing is generated in the region close to the leading edge for all the studied incidence angles. Additional lift is created in the region close to the root chord rather than the tip chord, whereas drag forces increases from tip to root. This can be attributed to the formation of trailing edge vortexes due to the flow separation at the wing leading edge that produces more drag, hence suppressing lift. The study showed also that angle of attack increases the drag coefficient from tip to root, especially at high angle of attack, indicating unfavourable behaviour for manoeuvring. Moreover, the angle of attack increased the pitching moment coefficient up to 10° before it drops sharply until it reaches the tip of the wing model. [ABSTRACT FROM AUTHOR]

The flow around curved tandem cylinders of equal diameter has been investigated for the first time, by means of direct numerical simulations. A convex configuration was used. The nominal gap ratio was L/D = 3.0 and a Reynolds number of 500 was chosen. Due to the change in effective gap ratio along the cylinder axis, there is a variation of tandem flow regimes, from alternating overshoot/reattachment, via stable reattachment, to co-shedding, in this case called gap shedding. The combination of reattachment and gap shedding gives near-zero drag and vertical forces for the downstream cylinder, whereas the corresponding forces on the upstream cylinder are comparable to single curved cylinders. Meanwhile, the opposite is true for the lift forces. A low-frequency variation of horizontal and vertical forces is seen, and this is attributed to a slow variation of the position where gap shedding commences. Finally, the concept of a critical angle is proposed to describe the transition to gap shedding, for a given combination of nominal gap ratio and Reynolds number. [ABSTRACT FROM AUTHOR]

Though interstellar dust mass is negligible compared to the stars and the interstellar gas, it is in continuous contact with the rest of the world instead of being an isolated entity. Interstellar dust mass significantly influences the star formation process and its appearance. Hence it is important to study how it interacts with its environment. Here, we try to understand the motion of interstellar dust grains in the presence of the forces, viz., the drag force due to the interstellar gas and the radiation pressure due to a nearby star. [ABSTRACT FROM AUTHOR]

At stations, high-speed trains frequently pass through the platform without stopping, where a combination of two island platforms represents the most common layout. The interaction between the train and the platform leads to certain problems, such as reductions in the comfort of the waiting environment and the safety of people around the platform. However, in the literature, there are few studies on the aerodynamic response between the train and the platform and on the airflow field characteristics above the platform when the train passes through the platform under different crosswind speeds. Therefore, we attempted to fill this gap using numerical methods to study the aerodynamic characteristics of the train passing through island platforms at 350 km/h under different crosswind speeds (10, 15, 20, 25, and 30 m/s). The aerodynamic response of high-speed trains combined with the flow field distribution is discussed in depth. We studied the wind speed distribution at different longitudinal distances above the platform, and obtained the position of the maximum wind speed when the head and tail car passed through the platform. Based on this, the wind speed distribution at different lateral distances above the platform was studied, and the reasons for the airflow changes above the platform were analyzed. The research results show that when a train enters a platform at 350km/h under a crosswind speed of 30 m/s, the reductions in the drag and lateral force of the whole vehicle reach their maximum, which are 50.44% and 66.51%, respectively. However, the change trend in the whole car lift force is opposite to that of the drag and lateral force, which increase when the train enters the platform and decrease when it leaves the platform. The largest growth in lift force is 102.39%, which occurred at a wind speed of 30m/s. The airflow velocity above the platform will increase rapidly as the head and tail car pass through the platform. A higher crosswind speed will result in the monitoring point of platform reaching its maximum airflow speed to an earlier time as the tail car passes through the platform. Meanwhile, we found that the lateral distance 1 - 2m above the platform is the area with the largest wind speed attenuation. [ABSTRACT FROM AUTHOR]

Aggregation of fluidization media may appear at the dense phase region of the pant-leg fluidized bed near the incline walls. When the particles flow along the inclined wall, the friction and drag force will cause the particles to accumulate on the inclined wall, resulting in an uneven distribution of particles. The stagnant zones can be minimized by correctly arranging secondary air. Computational particle fluid dynamics (CPFD) method was used to simulate the gas-solid two-phase flow pattern in the dense phase region of pant-leg fluidized bed. Cold tests were performed on a benchtop pant-leg fluidized bed. A high speed imaging technology was used to monitor the flow pattern in the dense phase area, whereas the bubble size and residence time were compared to verify the accuracy of the simulation. The gas-solid flow patterns under various models were simulated. The influence of different secondary air velocities on the reduction of stagnant zone in the dense phase zone of the fluidized bed were predicted. The results indicated that the introduction of secondary air could effectively promote the mixing of particles, and weaken the accumulation of particles on the inclined wall surface. Moreover, secondary air can effectively promote the flow between the gas-solid two-phases and improve the combustion characteristics in the furnace. [ABSTRACT FROM AUTHOR]

The commercialization of nanotechnology is significant in the areas of pharmaceutical delivery, supercapacitors, catalysts, microelectronics, thermal energy plants, automotive cooling, fuel cell membranes, crack-resistant paint, and water purification. Here Darcy-Forchheimeir hydromagnetic flow of radiative Williamson trihybrid M O S 2 + Z r O 2 + G O / E t h y l e n e g l y c o l nanofluid subject to entropy generation is investigated. Molybdenum disulfide M O S 2 , zirconium dioxide Z r O 2 , and graphene oxide G O nanoparticles in base fluid (Ethylene glycol) are incorporated. Darcy-Forchhiemeir porous medium and dissipative heat transfer attributes are considered. Furthermore, the convective boundary condition is incorporated for the analysis. Thermal radiation is employed to perform a study of the energy transfer phenomenon while keeping in mind the practical applications. The governing PDEs are converted into ODEs by appropriate transformations. Using the homotopy analysis method (HAM), the resulting non-dimensional systems are addressed analytically. The implications of various factors on the thermal transmission rate and friction factor for tri-hybrid M O S 2 + Z r O 2 + G O / E t h y l e n e g l y c o l nanofluid, hybrid M O S 2 + Z r O 2 / E t h y l e n e g l y c o l nanomaterial, and nanoliquid M O S 2 / E t h y l e n e g l y c o l are investigated through tables. Further, the fluid velocity, temperature, entropy rate, and Bejan number for all three nano-liquid scenarios in response to influential parameters (Weissenberg number We , magnetic parameter M , radiation parameter Rd , Brinkman number Br , suction parameter S , Darcy-Forchheimeir number Fr , and Biot number Bi) are graphically evaluated. The fluid velocity declines as the suction parameter grows. A greater Weissenberg number results in an increased Bejan number. Temperature and entropy rate increase with a higher magnetic value. A greater Weissenberg number results in an enhanced drag force. The rate of heat transmission decreases with an increasing radiation effect. In conclusion, the current outcome is an excellent invention of the results that came before it. [ABSTRACT FROM AUTHOR]

The gas-liquid two-phase flow with interfacial behaviors and bubble-liquid interactions is widely encountered in industrial processes such as that in gas-liquid reactors. The complicated phase structure makes it difficult to be modeled. The present work proposes a multi-scale mathematical model to simulate the bubbly flow in a square column. The volume of fluid (VOF) method is applied to treat the separated interface, and the discrete bubble model (DBM) is incorporated to handle the dynamics of dispersed bubbles. The hybrid model is validated against the benchmark experimental data to study the accuracy and suitability of the modeling framework for bubbly flows. And the influence of interphase forces on bubbly flow patterns and velocity profiles is investigated. It is found that the employment of both pressure gradient force and Ishii-Zuber drag model provides fairly good agreements with experimental data for velocity profiles. [ABSTRACT FROM AUTHOR]

In real life applications, variations in diffusivity properties are incorporated in order to estimate accurately the transfer rate of heat/mass. This phenomenon has significant impact on liquid diffusion, electronics, moisture migration process, building insulation, vapors diffusion. Thus, present analysis based on the Darcy Forchheimer theory is introduced to study the stagnation flow mechanism in a rotating disk. The nanoparticles to be saturated are illustrated by the constitutive relationship of a second grade fluid. The flow is also subjected to hydro-magnetic phenomenon. Nonlinear stratification along with varying features of thermal conductivity is incorporated for the better understanding of variations in heat transport process. Variable character of thermophoretic and Brownian diffusions on the nanoparticles transportation in the base fluid is also discussed. The features of solutal slip and thermal jump are exercised to examine the mass and heat transfer. Thermal radiation as well as chemical reaction is also assumed in transport equations. The equations govern the physical process are made non-dimensional by introducing appropriate variables. An analytical series solutions are then achieved using a convergent scheme. The behaviors of dimensionless involved constants on flow fields are depicted through graphs. Rates of heat and mass transfers and drag force are also studied through graphical description. In this study, it is concluded that the minimum temperature exists corresponding to higher thermal stratified and temperature jump parameters. Larger inertia parameter enhances the both radial and tangential velocity components. Higher diffusive parameter intensifies the concentration function. [ABSTRACT FROM AUTHOR]

This paper presents a dynamical analysis of a tethered aerostat using a multibody simulation tool called SimscapeMultibody™. Tethered aerostats are lighter than air vehicles that float in the air and are connected to the ground through the tether. Atmospheric winds are a source of disturbance to the aerostat. The wind produces drag force that causes the aerostat to displace from its mean position. This phenomenon is called blow-by. Solving the mathematical model of the motion dynamics with time step is the conventional method used for simulating the flight dynamics of the aerostat. This paper discusses the application of Simscape Multibody™ for the three-degrees-of-freedom flight dynamic simulation of spherical tethered aerostat. Simscape Multibody™, an extension of MATLAB®/Simulink, is a multibody modeling tool in which physical bodies and their interactions have to be defined to simulate the dynamics. The mathematical model of the defined system is automatically generated by the SimscapeMultibody™ solver, and the system dynamics is simulated. The simulation of dynamics using multibody modeling tools provides high fidelity simulation for the tethered aerostats. [ABSTRACT FROM AUTHOR]

Fluids like hybrid nanofluids have great potential that present exceptional thermal behavior and thermophysical properties as compare to ordinary nanofluids. Hybrid nanofluids are obtained by the mixture of two different nanoparticles in a base fluid. Many scholars stated that hybrid-nanofluids could be replaced by conventional coolants, especially fluids which work at high temperature. Therefore, these kinds of nanofluids are less damaging for environmental impact and also lead to save energy. The main idea of hybrid nanofluids is to develop performance of heat transfer and its advantages has directed to comparatively good hope for its applications. The objective of present article is to examine 3D stagnation point flow of hybrid nanofluid passes along a stretchable heated wavy cylinder under the impact of variable thickness and slip conditions. For this purpose we consider alloy particles of AA7075 + AA7072 and AA7072 which are suspended in methanol liquid. The alloy particles merged in this analysis are entirely manufactured materials as well as possessing higher heat transfer characteristics. Alloy AA7072 is a combination of zinc and aluminum in ratio 1:98 with addition of metals like silicon, copper and ferrous. Similarly, alloy AA7075 is a combination of zinc, aluminum, copper and magnesium in ratio −6, −9, −1 and −3 respectively with addition of metals like silicon, magnesium and ferrous. The scenario of this model is scrutinized mathematically by captivating induced magnetic field with in the domain of thermal boundary layer. Similarity transformations are deployed to change the governing equations into nonlinear ODEs and consequently solved this system through bvp4c solver. The impact of emerging parameters on velocity, induction and energy distributions are examined through graphical depiction. Furthermore, heat transfer rates and drag forces near the boundary are designed numerically in tabular form. [ABSTRACT FROM AUTHOR]

If flow velocity equals sound velocity, base drag coefficient is a significant part of drag coefficient and it depends on variety of flow and geometrical parameters. Drag, base drag, drag coefficient and base drag coefficient for four bodies with same width, height and length and different shape are estimated by CFD (ANSYS Fluent) at high speeds. For different rear surface curvature, at high flow velocity, share of base drag at drag of body and flow field as contour of vector of velocity coloured by pressure are shown and analysed. [ABSTRACT FROM AUTHOR]

The concept of towable horse trailers and caravans has become increasingly common for transporting horses around the country as well as for providing a comfortable and mobile living space during vacations. It is very common for the towing vehicle to double its fuel usage by towing a horse trailer or a caravan. The massive increase in fuel consumption is mainly due to the changed aerodynamics. To optimise the design of the trailer and reduce fuel consumption, it is essential to know the high drag contribution surfaces and appropriately modifying them. In the present study, two different industrial models of the horse-trailer have been evaluated and optimised for their aerodynamic drag. Both trailers have a different front design which can represent almost all-important feature changes to estimate the drag contribution and prediction of the best-optimised shape. The challenge is to reduce the drag force without reducing the internal accommodation space and meeting the legal specifications. The front shape of the trailer, roof and different add-on devices has been tested and drag performance has been evaluated. The length of the wake region has been improved by providing a roof curvature and diffuser at the top and bottom rear side of the trailer. Providing a roof curvature on the trailer roof has delayed the flow separation at the rear end of the roof by reducing the adverse pressure gradients. The wake behind the car is found sensitive to the gap between the car and trailer. Adverse pressure gradient has been recovered in the wake region by using add-on devices. This resulted in the conclusion that fuel consumption has been reduced to a significant percentage. [ABSTRACT FROM AUTHOR]

The wing of missile can be considered as an effective factor for determination of lift to drag ratio. However, there are few studies that investigate wing effect on missile aerodynamics. Therefore, the purpose of this study is to indicate wing effect on the missile aerodynamics and optimize wing geometry for enhancement of aerodynamic efficiency. The missile designed tail-fin configuration is selected from a previous study which contains experimental data. In the beginning of study, Computational Fluid Dynamics (CFD) simulations of selected missile are performed and compared with experimental data. Wing is then mounted to the selected missile and CFD solution is repeated for modified missile at 6º angle of attach (AoA) and subsonic and supersonic speeds. The modified missile shows good performance in point of aerodynamics when compared with baseline missile model. In addition, wing geometry is optimized to improve aerodynamic performance using Multi-Objective Genetic Algorithm (MOGA). Objective functions are determined as lift and drag coefficients. Wing geometry parameters are determined as design variables for optimization. After the optimization process, the results are showed that the aerodynamic coefficients are improved when compared with baseline geometry. In addition, response surface analysis is presented to show which design parameters are more effective on drag and lift forces. The findings of study show that optimum results are more efficient in terms of performance. CFD solution method and the optimization procedure can be applied to design or optimize for different geometry. [ABSTRACT FROM AUTHOR]

In the present work, the laminar flow through a circular cylinder with two crossed splitter plates is analyzed. The characteristic-based method has been used along with the unstructured grid. The current research has been done to detect the proper conditions according to the geometrical parameters in which the optimal heat transfer is taking place. Geometric control parameters are the angle of splitter plates (\theta) and the ratio of length of the splitter plate to cylinder radius (n=L/D). It was found that the use of a two-branched splitter plate is not wise in Reynolds number less than 100 due to its insignificant effect in flow properties. In angle 30° between two plates, the least drag force is witnessed with respect to other angles. Application of double branched splitter with angles more than 60° is not recommended, which will increase the total drag significantly. Since the splitter plate increases, the overall heat transfer from the cylinder and splitter set is enhanced. Minimum drag over the cylinder, and maximum convection drop from it is taken place when the dimension length is 0.75. Between dimensionless lengths 1.25 and 1.5, the Nusselt number oscillates with least amplitude and such behavior is also observed when two splitters are 60°apart. [ABSTRACT FROM AUTHOR]

A method is proposed to investigate the steady deformation and the drag of a single droplet in a flowing gas at a high Reynolds number. The volume of fluid (VOF) method is used to model the droplet surface structure. The direct numerical simulation (DNS) method is used to model the gas flow field. In order to avoid the effect of the droplet acceleration on the drag and reduce the computation cost, a body force is added to the droplet to make it fixed at a constant position. The body force is determined by using the Newton iteration procedure. The simulated droplet aspect ratio and the drag coefficient agree well with the published experimental data. Meanwhile, the sources of the drag are analyzed and the effect of the Reynolds number and the Weber numbers on the droplet deformation and the drag are studied. The drag mainly comes from the pressure difference between the droplet-leading zone and the trailing zone, and the turbulence wake would increase the drag. [ABSTRACT FROM AUTHOR]

Copyright of Caderno Brasileiro de Ensino de Física is the property of Caderno Brasileiro de Ensino de Fisica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work, three-dimensional Euler-Lagrange (EL) point-particle simulations of a shock wave interacting with a fixed bed of particles are carried out. The results from the particle-resolved (PR) simulations are used to assess the performance of the point-particle drag models during short time scales. We demonstrate that in a one-way coupled regime, the point-particle simulations recover the dominant gas dynamic features of the flow and are in a good agreement with the exact Riemann solution of a shock traveling through a sudden area contraction. Although the PR simulations are inviscid, we show that a dissipative drag is necessary to predict the mean behavior of the gas. As a model for the inviscid shock-induced (SI) drag two different models are presented in lieu of the quasi-steady drag. Finally, two-way coupled simulations are performed at four different particle volume fractions {0.10, 0.15, 0.20, 0.25} and three different incident shock Mach numbers {1.22, 1.66, 3.0} and compared against the data from PR inviscid simulations. At a lower Mach number (1.22), averaged flow quantities from the two-way coupled simulations agree well with the PR simulations. As the Mach number increases, we observe that the discrepancies between the point-particle and the PR simulations grow. A sensitivity analysis of the drag models involved reveals a strong influence of the inviscid-unsteady force on the gas quantities especially in the case of a strong shock interacting with a dense bed of particles. The use of Mach correlation beyond the subcritical regime coupled with the model for volume fraction correction is identified as a probable cause for the additional drag. [ABSTRACT FROM AUTHOR]

Copyright of Revista Portuguesa de Ciências do Desporto is the property of Universidade do Porto, Faculdade de Desporto and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, the feature of stagnant Sutterby nanofluid towards a wedge surface is analyzed under the impact of a variable external magnetic field. Instead of the traditional Fourier law, the realistic Cattaneo-Christov principle is incorporated in the energy equation to scrutinize the heat flow pattern by utilizing the non-homogeneous two-phase nanofluid model. The constitutive flow rules are transfigured into a nonlinear differential system via feasible mathematical alterations. Methodologically, the bvp4c numerical procedure is employed properly to derive accurate numerical solutions for the present boundary flow problem. By varying the values of the involved parameters of the governing equations, the behaviors of temperature, velocity, and concentration profiles are described graphically and interpreted thoroughly. In this attempt, the major finding is that the magnetic field accelerates the motion and declines the temperature and concentration fields in the performance of suction and injection. Moreover, the nanofluid parameters upsurge the heat transfer mechanism and decline the mass transport and the effect of drag forces in both situations of wall-through flow (i.e., suction and injection effects). Furthermore, the nanofluid concentration profile decays due to the strengthening in the thermophoresis phenomenon. As a useful application, the magnetic function trend along with the thermophoresis diffusion on the nanofluid flow field may be exerted broadly in the field of aerosol technology. [ABSTRACT FROM AUTHOR]

• Hydrodynamics of DFB gasifier were investigated by means of experiment and CFD. • CFD simulation results show reasonable agreement with experimental data. • Simulation results were presented in terms of the pressure profile, solids hold-up and solid circulation rate Thermo-chemical conversion of biomass using Dual Fluidized Bed (DFB) gasifier is proven to be a promising way for the production of H 2 rich syngas. In the present work, the hydrodynamics in the DFB gasifier is investigated experimentally and with Computation Fluid Dynamics (CFD) at cold flow conditions. Three-dimensional Eulerian-Eulerian multi-phase model combined with the kinetic theory for the granular phase has been applied to investigate unsteady-state behaviours of a DFB gasifier. The developed CFD model is validated with experimentally obtained pressure distributions across the riser. The model prediction shows deviation from experimental results (10-14%), which are mainly due to the Gidaspow drag model over predicting drag force. Simulation results are presented in terms of the pressure profile, solids hold-up and solid circulation rate. [ABSTRACT FROM AUTHOR]

The bubble drag force correlation plays an important role in the numerical simulation accuracy of gas/liquid flows. In order to systematically investigate the interphase drag force of non-buoyancy driven bubbly flows, a dynamic-positioning body force (DPBF) method is developed in this study. It is proved that this method has an enough computation precision. Using this method, a series of direct numerical simulation (DNS) cases of a single bubble with low-intermediate Re(1 ≤ Re ≤ 200) and a bubble swarm with low Re(5.6 ≤ Re ≤45) are carried out and the bubble drag coefficients are calculated. Based on all the DNS data, the drag correlations with dimensionless parameters (Re, We for a single bubble and Re, We, gas fraction for bubble swarm) are systematically investigated and reported in this paper, which can provide a reference to the development of drag force closure model for non-buoyancy driven bubbly flows. [ABSTRACT FROM AUTHOR]

The article presents the research on the topic of system limit was first proposed by Tek in 1959 and the work extended the approach by Souders and Brown by incorporating concepts of drop stability developed by Hinze. Topics include the work by Hinze showed that there was a definite correlation between the maximum stable droplet size of liquid droplets entrained in vapor, and the Weber number relates the drag force on droplet in a vapor stream to the cohesive force that hold a droplet together.

Flow around a cube is numerically studied in the laminar vortex shedding regime. The objective is to examine the three-dimensional vortex shedding mechanism and understand the temporal behavior of the wake. Vortices were identified using λ2 criterion for Re = 250-770. The wake of the cube sheds paired hairpin vortices, which moves in the streamwise direction and attains a constant shape with time. The analysis of separation distance and angular orientation of hairpin vortices for flow around a cube are presented here for the first time in the literature. The separation (d) between the paired hairpin vortices scales as t-1/2⁠. The orientation of hairpin vortices changes with time and attains a near-normal orientation with respect to the axial direction. At Re ≥ 339, the hairpin twists with respect to axial direction losing the axisymmetry in one plane noted for 276 ≤ Re ≤ 300. The hairpin vortices disintegrate into smaller vortices at higher Re = 570 and 770. A quasi-periodic nature of the flow has been revealed by the phase plots. The drag and side forces generated due to the flow are studied with pressure force mostly contributing to the drag. One of the side force coefficients dominates owing to the asymmetry of the wake in one plane and symmetry in the other orthogonal streamwise plane. These results clearly bring out the asymmetric nature of flow in the shedding regime. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• Experiment for ripple generation in an oscillating water tank are conducted. • The 3D DEM-MPS is applied to simulate ripple formation under resonance condition. • Pressure by the gradient of water surface is of importance to the ripple formation. • Accurate evaluation of free surface flows is needed for simulating ripple formation. The height of ripples, representing roughness in the shallow-water area, is an important factor in the prediction of coastal processes. However, the characterization of ripples under violent flow conditions has proven challenging. For instance, in shallow water in the swash zone, significant water fluctuation occurs owing to interactions between the up-rush and down-rush of waves. Because such phenomena shows strong nonlinearity, sufficient knowledge of swash-ripple formation remains lacking. In this study, experiments generating ripples in an oscillating water tank are conducted. Furthermore, numerical simulation using the three-dimensional DEM-MPS coupled method is performed. By comparing numerical and experimental results, validation of the present numerical simulation is demonstrated, followed by an investigation of the mechanics of ripple formation. Numerical results show that not only the drag force but pressure gradient force resulting from the water surface gradient considerably affect sand-particle motion, revealing the need for accurate evaluation of the free surface flow. Moreover, pressure gradient force plays an important role in the ripple formation process, so it should be reflected in the numerical model for ripple simulations. [ABSTRACT FROM AUTHOR]

In order to improve the transportation efficiency and safety of the vertical hydraulic transport pipe, a new type of pipeline transport system with helical blade is proposed in this paper. Based on CFD-DEM coupling method, the liquid-solid two phase flow characteristics are analyzed for the swirling pipes and no blade pipe. The study focuses on the effect of the different helix angles of helical blade pipes in terms of the distributions of fluid velocity, the fluid vprticity, the total pressure, the particle's local concentration, the drag force and kinetic energy of particles. Subsequently, the transport efficiency is measured based on the starting speed of particles and the particle concentration, and the safety of the particle transportation is evaluated based on the flow structure and the kinetic energy of particles. It is found that the tangential velocities of the swirling pipes are clearly larger than that of the case of no blade pipe, and the swirling number decreases as the increasing of helix angle of helical blades within swirling pipe. As the decreasing of helix angle, the vorticity magnitude increases sequentially, and tie vortex core structure of the flow field is gradually enriched. Meanwhile, the total pressures for the swirling pipes decrease rapidly after the fluid enters the helical blades region, reflecting the difference energy efficiency of the swirling pipes. Furthermore, the swirling pipe accelerates the starting speed of the particle, and the i increases the particle concentration in the pipe while making the particle spatial flow structure better and the particle kinetic energy larger. In general, the swirling pipe makes the particle transportation more efficient and safe. [ABSTRACT FROM AUTHOR]

Aquatic vegetation can significantly affect flow structure, sediment transport, bed scour and water quality in rivers, lakes, reservoirs and open channels. In this study, the lattice Boltzmann method is applied for performing the two dimensional numerical simulation of the flow structure in a flume with rigid vegetation. A multi-relaxation time model is applied to improve the stability of the numerical scheme for flow with high Reynolds number. The vegetation induced drag force is added in lattice Boltzmann equation model with the algorithm of multi-relaxation time in order to improve the simulation accuracy. Numerical simulations are performed for a wide range of flow and vegetation conditions and are validated by comparing with the laboratory experiments. Analysis of the simulated and experimentally measured flow field shows that the numerical simulation can satisfactorily reproduce the laboratory experiments, indicating that the proposed lattice Boltzmann model has high accuracy for simulating flow-vegetation interaction in open channel. [ABSTRACT FROM AUTHOR]

This paper presents experimental and numerical investigations on the modification of local spanwise skinfriction over triangular riblets under the total drag reduction condition. Specifically, the mean and fluctuating vortical flow fields were measured using 2-components X-wires and computed using LES, respectively. Besides, the relationship between local skin-friction along the riblet spanwise and associated vortex evolution was also built using the vortex dynamic method. Based on these results, it was found that, compared with the smooth case, the impaired and enhanced vortex strength, and resultant viscous diffusion/energy dissipation, determined the reduction and augment of the viscous drag force over the local spanwise riblet groove, i.e., decreasing and increasing cases of local drag, respectively. Furthermore, the mean normal diffusion fluxes of normal and spanwise vorticities contributed more to the viscous drag under these two cases. Correspondingly, the relevant flow physics related to these phenomena was discussed in detail. [ABSTRACT FROM AUTHOR]

Because the pumping of samples by viscous drag forces and the use of flow-focusing for several sheath flows are widely used in microfluidic devices applications, the present investigation treats about the transport of multilayer immiscible viscoelastic fluids into a slit microchannel by electro-osmotic and pressure-driven effects. The mathematical formulation for the steady-state analysis of the flow field is based on the Poisson–Boltzmann equation and the Cauchy momentum equation. Each fluid layer has independent physical and electrical properties and is formed by a mixture of an electrolyte with a fluid that provides a viscoelastic behavior that follows the simplified Phan-Thien-Tanner (sPTT) rheological model. In the problem, the fluids are conductive and the walls of the microchannel are dielectrics, yielding electric double layers in the liquid–liquid and solid–liquid interfaces; therefore, the flow field is controlled by interfacial electrostatic conditions. The semi-analytical results are centered in the description of the velocity profiles and in the flowrate as a function of a series of dimensionless parameters arising from the mathematical modeling, where we can observe that the multilayer flow characteristics are related to the type of electrolyte solutions, since when the flow field is formed by two or more, interesting interfacial effects appear that modify the shape of velocity profiles and change the magnitude of flowrate in favor or against, depending of the positions of each fluid layer; in addition, the flow raises or diminishes by applying an external pressure gradient. [ABSTRACT FROM AUTHOR]