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Water erosion study is regarded as one of the most important axes in scientific researches. The erosive effect of water on the surface layers can have major consequences on soil loss and land degradation. The objective of our work was the development of a water erosion nomograph that represents a practical and precise tool that is adapted to local conditions for a direct quantification of erosive action in the absence of basic data. Regarding the magnitude of the phenomenon in Algeria, the catchment of Wadi Cheliff was taken as an experimental site where a significant spatiotemporal variability of liquid and solid flows was observed and the measurement network in different locations was either dispersed or non-existent. The developed methodological approach permitted the identification of 149 experimental sites (20 hydrometric stations, 15 large dams and 114 hill dams) where existing data allowed the erosion quantification. A flow coefficient variography was performed in addition to a principal component analysis (PCA), leading to the identification of three distinct groups. Moreover, the modeling of the studied variable was achieved through the application of multivariate analysis to the third group of 100 observations. Applying the principles of nomography on the final model, a nomograph of the semi-arid area of Wadi Cheliff catchment was realized for surfaces ranging from 500 to 25 000 ha. This nomograph enabled the direct quantification of water erosion from the product (Es1 x Es2), taking into account the area of the catchment, its average slope and its flow coefficient with a mean absolute percentage error (MAPE) of 2%. [ABSTRACT FROM AUTHOR]

A novel method has been proposed to design inlet gauzes in single-stage low-speed simulation compressor experiments. The aim is to investigate the method for designing inlet profiles and understand how they affect the repeatability of the compressor. Based on the inlet gauzes, the effect of the inlet profile on the compressor repeatability and its flow mechanisms was investigated by the experiments. The experiment results show that, for the single-stage low-speed compressor, as the inlet flow coefficient decreases, the loss and blockage near the rotor casing caused by the tip leakage flow are enhanced, resulting in an increase in the local absolute velocity and the total pressure. Meanwhile, the radial migration of the secondary cross flow in the stator is enhanced, leading to a thinner boundary layer at the stator outlet near casing region. Consequently, the flow capacity near the casing at the compressor outlet is enhanced with a decrease in the inlet flow coefficient. Given that the flow structure and the local loss of the compressor are not sensitive to the inlet profile at the near-choked condition, employing the inlet profile generated based on the compressor outlet profile at the near-stall condition can simulate the repeating stage environment accurately in the single-stage low-speed compressor experiment. [ABSTRACT FROM AUTHOR]

Intracranial aneurysms are nowadays treated with endovascular flow diverter devices to avoid sac rupture. This study explores how different linear and quadratic hydrodynamic resistance parameters reduce the flow in the sac for five patient-specific sidewall aneurysms.The 125 performed blood flow simulations included the stents using a Darcy-Forcheimer porous layer approach based on real-life stent characteristics. Time- and space-averaged velocity magnitudes were strongly affected by the linear coefficient with a power-law relationship. Quadratic coefficients alter the flow in a minor way due to the low-velocity levels in the aneurysm sac and neck region. [ABSTRACT FROM AUTHOR]

In Nuclear Power Plants (NPPs), online condition monitoring and the fault detection of structures, systems and components (SSCs) can aid in guaranteeing safe operation. The use of data-driven methods for these tasks is limited by the requirement of physically consistent outcomes, particularly in safety-critical systems. Considering the importance of regulating valves (e.g., safety relief valves and main steam isolation valves), this work proposes a multistage Physics-Informed Neural Network (PINN) for fault detection in such components. Two stages of the PINN are built by developing the process model of the regulating valve, which integrates the basic valve sizing equation into the loss function to jointly train the two stages of the PINN. In the 1st stage, a shallow Neural Network (NN) with only one hidden layer is developed to estimate the equivalent flow coefficient (a key performance indicator of regulating valves) using the displacement of the valve as input. In the 2nd stage, a Deep Neural Network (DNN) is developed to estimate the flow rate expected in normal conditions using inputs such as the estimated flow coefficient from the 1st stage, the differential pressure, and the fluid temperature. Then, the residual, i.e., the difference between the estimated and measured flow rates, is fed into a Deep Support Vector Data Description (DeepSVDD) to detect the occurrence of faults. Moreover, the deviation between the estimated flow coefficients of normal and faulty conditions is used to interpret the consistency of the detection result with physics. The proposed method is, first, applied to a simulation case implemented to emulate the operating characteristics of regulating the valves of NPPs and then validated on a real-world case study based on the DAMADICS benchmark. Compared to state-of-the-art fault detection methods, the obtained results from the proposed method show effective fault detection performance and reasonable flow coefficient estimation, thus guaranteeing the physical consistency of the detection results. [ABSTRACT FROM AUTHOR]

The wettability of shale reservoirs has an important influence on the flow of external fluids. In this paper, the effect of wettability on the self-absorption of hydraulic fracturing fluid under different pore size conditions is first analyzed. Then, the mechanism of the influence of wettability pore size on the flow coefficient is elucidated. The results show that (a) as the pore size decreases, the importance of various forces acting on the fluid during the flow process changes, and the solid-liquid interaction will greatly affect the fluid flow in the nanopore. (b) When the radius is 5, the flow enhancement increases from 0.6331 to 0.998 as the radius increases from 0 to 3.141594.(c) The shale inorganic material contains a variety of minerals, and the interaction forces between different mineral surfaces and water molecules are different, resulting in different apparent viscosities. • The influence of wettability on hydraulic fracturing fluid imbibition is analyzed. • The effect of different pore size conditions is considered. • The wettability pore size influence mechanism of flow coefficient is clarified. [ABSTRACT FROM AUTHOR]

Purpose: To guide the stable radius clearance choice of water-lubricated bearings for single screw compressors, this paper aims to analyze the effects of turbulence and cavitation on bearing performance under two conditions of specified external load and radius clearance. Design/methodology/approach: A modified Reynolds equation considering turbulence and cavitation is adopted, based on the Jakobsson–Floberg–Olsson boundary condition, Ng–Pan model and turbulent factors. The equation is solved using the finite difference method and successive over-relaxation method to investigate the bearing performance. Findings: The turbulent effect can increase the hydrodynamic pressure and cavitation. In addition, the turbulent effect can lead to an increase in the equilibrium radius clearance. The turbulent region exhibits a higher load capacity and cavitation rate. However, the increased cavitation negatively impacts the frictional coefficient and end flow rate. The impact of turbulence increases as the radius clearance decreases. As the rotating speed increases, the turbulence effect has a greater impact on the bearing characteristics. Originality/value: The research can provide theoretical support for the design of water-lubricated journal bearings used in high-speed water-lubricated single screw compressors. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2024-0029/ [ABSTRACT FROM AUTHOR]

This article employed numerical methods to investigate the aerodynamic, thermal, and infrared characteristics of last-stage turbine swirl on a two-dimensional convergent divergent (2D-CD) exhaust system with an afterburner under varying bypass ratios. The research results indicate that the swirl diminishes the thrust coefficient and flow coefficient of the 2D-CD exhaust system with an afterburner. At a bypass ratio of 0.2, the thrust coefficient and flow coefficient decrease by 0.65% and 1.07%, respectively. When the bypass ratio is relatively small, the swirl flow leads to a decrease in the temperature of the afterburner heat shield. Conversely, when the bypass ratio is relatively large, the opposite occurs. The maximum temperature of the heat shield increases by up to 7.2% (bypass ratio = 0.35), while the average temperature decreases by up to 7.1% (bypass ratio = 0.2). The swirl causes an increase in the temperature of the divergent section heat shield, with the most significant deterioration observed at a bypass ratio of 0.25, resulting in a maximum temperature increase in 12.2%. Swirling flow shortens the length of the jet flow, and as the bypass ratio reduces, this attenuation effect becomes more pronounced. When the bypass ratio is 0.2, the length of the core area decreases by 40.3%, and the infrared intensity of the narrow-side jet flow decreases by 12.5%. Overall, on the XOY detection plane, the maximum decrease in infrared intensity is 11.5%, and the maximum increase is 11.7%. On the XOZ detection plane, the maximum decrease in infrared intensity is 15.9%, and the maximum increase is 5.7%. [ABSTRACT FROM AUTHOR]

Swirling flow at vertical shaft spillways results in flow fluctuations, reduces hydraulic system efficiency, and causes structural damage. Optimizing the shape of the inlet is a practical means to decrease the swirling flow strength. In the present study a comprehensive experimental investigation was performed to examine the effects of a new type of inlet over vertical shaft spillways, namely the circular piano-key (CPK) inlet, for free, orifice and full-pipe or black water flow regimes. Head-discharge relationships, threshold and critical submergence depths and the effects of different geometrical parameters of the CPK inlets on the spillway flow discharge coefficient were assessed. Results reveal that increases in the height of the inlet and outlet keys increase the released capacity of the shaft spillway. Given its increased total crest length and the effects of the radially placed walls of a CPK against the swirling flow, angles of the inlet and outlet keys of the CPK are found to significantly affect the spillway flow discharge. The effect of inlet and outlet overhangs on the efficiency of CPK inlets is not noteworthy, being negligible. Considering the destructive effects of swirling flow, the CPK inlets significantly decrease the range of submergence for an unfavourable swirling flow regime condition, increasing the threshold submergence depth and decreasing the critical submergence depth. The flow discharge through the CPK inlets is higher than those of the other circular-type spillways. The present modified CPK inlets more effectively divert water, serving as an economical alternative to the conventional circular spillways. [ABSTRACT FROM AUTHOR]

As the key heat transfer element of natural draft dry cooling towers, the columnar cooling tube bundle radiator is composed of four rows pipe or six rows pipe, and usually arranged as per delta, which would induce a large vortex around the delta under crosswind conditions, and then impact the cooling performance of cooling deltas and that of the total Tower. To overcome this shortage, this study proposed a cooling column with a gap between the upstream pipes and downstream pipes in one cooling column, which can introduce a stream of air jet flow into the columnar cooling tube bundle and then impact the aerodynamic field of the tube bundle and the corresponding cooling delta. A three-dimensional numerical model has been established to compare and study the cooling characteristics of the cooling columns with wedge-shape gap and the usual. The results show that the wedge gap can increase the heat transfer coefficient of the radiator and decrease its flow resistance coefficient. At 7 m/s crosswind, the outlet water temperature of dry tower by using the usual radiator is 36.46 °C, while that is 34.23 °C for dry cooling tower with wedge radiator. [ABSTRACT FROM AUTHOR]

Due to the presence of tiny gaps at the interface of two layers of saturated soil, water seepage occurs at a slower rate within these gaps, resulting in laminar flow at the interface. Based on the Hagen‐Poiseuille law, a general imperfect flow contact model was established for layered saturated soil interfaces by introducing the flow contact transfer coefficient Rω and the flow partition coefficient ηω. The investigation focused on the thermal consolidation behavior of layered saturated soil foundations under variable loadings considering the flow contact resistance effect at the interface. By employing the Laplace transform and its inverse transform, a semi‐analytical solution for the thermal consolidation of layered saturated soil foundations was derived. In the context of a two‐layer soil system, the effects of Rω, ηω, and permeability coefficient k on the consolidation process were examined. The obtained results were then compared with three other interfacial contact models, thereby confirming the rationality of the presented model. The study findings revealed that the flow contact resistance effect leads to a clear jump in the pore water pressure. Furthermore, an increase in Rω and a decrease in ηω were found to significantly enhance displacement and pore water pressure, while having minimal impact on the temperature increment. These insights contribute to a more comprehensive understanding of the thermal consolidation behavior of layered saturated soil foundations and underscore the significance of accounting for the flow contact resistance effect in such analyses. [ABSTRACT FROM AUTHOR]

An experimental investigation of R245fa flow boiling in the horizontal flow (θ fd = 0°), vertical upward flow (θ fd = 90°), and vertical downward flow (θ fd = –90°) was carried out using a bare stainless-steel tube (BT) with an inner diameter of 10.02 mm and an effective heating length of 820 mm. The experimental condition was performed under a saturation pressure of 0.6 MPa, a heat flux varying from 4.99–74.60 kW/m2, a mass flux range of 197.94–696.63 kg/(m2·s), and a vapour quality range from 0.01 to 0.9. Five flow patterns, stratified flow, intermittent flow, churn flow, annular flow, and drying flow, could be observed in the experiment. When the heat flux was relatively low (q ≤ 15 kW/m2)), the variation of the heat transfer coefficient with flow direction was relatively gradual. However, when q ≥ 30 kW/m2, a distinct 'U'-shaped trend in the heat transfer coefficient is observed with the flow direction transitioning from vertical downward to horizontal and then to vertical upward. Due to the effect of buoyancy force, the heat transfer performance was relatively better at θ fd = –90° The friction pressure drop in the horizontal flow was the smallest, and the maximum value always occurred at θ fd = 90° Meanwhile, the experimental data for heat transfer coefficient and pressure drop was compared to the well-known correlations from the literature. The predictive correlation by Fang et al. for the heat transfer coefficient was in good agreement with the experimental data. Regarding frictional pressure drop, the Filho, Muller-Steinhagen and Heck and Zakaria correlations were recommended for pressure drop in horizontal flow, upward flow, and downward flow, respectively. [ABSTRACT FROM AUTHOR]

The paper proposes a theory of similarity of quasi-geostrophic vortices against the background of large-scale flows. This information is useful when planning laboratory and numerical experiments to study mesoscale and submesoscale vortex dynamics of vortices interacting with currents. Special attention is paid to studying geometric similarity of phenomena. It is revealed that the complete set of dimensionless similarity numbers of baroclinic vortices includes four dimensionless parameters: the dimensionless intensity of the vortex, the geometric similarity of the background flow (the ratio of the relative vorticity to the deformation coefficient of the background flow), the coefficient of horizontal stretching of the vortex core, and the coefficient of vertical oblateness of the vortex core coinciding with the Burger number. To describe the similarity of barotropic vortices against the background of barotropic flows, the number of necessary dimensionless parameters is reduced by one number: the coefficient of vertical oblateness of the vortex core is eliminated from consideration. When studying axisymmetric vortices or vortex structures close to axisymmetric, another geometric parameter of the vortex is eliminated from consideration—the coefficient of horizontal stretching of the vortex core. As a result, the maximum possible set of similarity parameters includes four dimensionless numbers, and the minimum is two. [ABSTRACT FROM AUTHOR]

The colloidal borescope, using colloidal particle motion, is used to monitor the flow velocities and directions of groundwater. It integrates advanced techniques such as microscopy, high-speed photography, and big data computing and enjoys high sensitivity at the micron level. However, In the same well, the groundwater flow velocity monitored by colloidal hole mirror is varies greatly from that obtained by conventional hydrogeological monitoring, such as pumping test. In order to solve this problem, the stability catcher and stratified packer are designed to control the interference of the vertical flow in drilling, and to monitor the flow velocity and direction of groundwater velocity at the target aquifer and target fracture. Five wells with different aquifers and different groundwater types were selected for monitoring in south-central China. The instantaneous velocity and direction are converted into east–west component and north–south component, the average velocity and direction is calculated according to the time of 10 min, and the particle trajectory diagram is established. Based on these results, it proposed a concept of cumulative flow velocity. Using curve-fitting equations, the limits of cumulative flow velocities as the monitoring time tends to infinity were then calculated as the actual flow velocities of the groundwater. The permeability coefficient of aquifer is calculated by using the fissure ratio of aquifer, hydraulic slope and flow velocity, and compared with the permeability coefficient obtained by pumping test. The results are as follows: (1) The variation coefficient of the instantaneous flow velocity measured at the same depth in the same well at different times is greater than that of the time average flow velocity and greater than that of the cumulative flow velocity. The variation coefficient of the actual velocity is the smallest, indicating that the risk of using the actual flow velocity is lower. (2) The variation coefficient of the flow rate monitored at different depths in the same well is mainly controlled by the properties of the aquifer. The more uniform water storage space in the aquifer, the smaller the variation coefficient. (3) The comparison between the permeability coefficient obtained by monitoring and the permeability coefficient obtained by pumping test shows that the flow of structural fissure water controlled by planar fissure is more surface flow, and the results are consistent. When the groundwater flow is controlled by pores and solution gaps, the flow channel is complicated, which is easy to produce turbulent flow, and the result consistency is poor. (4) According to different research accuracy requirements, different monitoring and calculation methods can be selected for different aquifers and groundwater types. Researches show that, the permeability coefficient calculated for the actual flow velocity in well DR01 is the same as that calculated for the pumping test. The aquifer characteristics reflected by the coefficient of variation of the actual flow velocity in the same aquifer are more realistic. The pumping test method obtains the comprehensive parameters of a certain aquifer, and this method can be used to monitor a certain fissure. In this paper, the new technology developed for monitoring, and the new algorithm established for data processing, can accurately obtain the flow velocity and direction of groundwater, using capsule hole mirror monitoring method. The key parameters of hydrogeology can be obtained by using one well, which can reduce the time and cost input and improve the work efficiency. [ABSTRACT FROM AUTHOR]

Existing models for estimating hyporheic solute mass flux often require numerous parameters related to flow, bed, and channel characteristics, which are frequently unavailable. We performed a meta‐analysis on existing data set, enhanced with high Reynolds number cases from a validated Computational Fluid Dynamics model, to identify key parameters influencing effective diffusivity at the sediment water interface. We applied multiple linear regression to generate empirical models for predicting eddy diffusivity. To simplify this, we developed two single‐parameter models using either a roughness or permeability‐based Reynolds number. These models were validated against existing models and literature data. The model using roughness Reynolds number is easy to use and can provide an estimate of the mass transfer coefficient for solutes like dissolved oxygen, particularly in scenarios where detailed bed characteristics such as permeability might not be readily available. Plain Language Summary: Current methods for estimating solute mass transfer across the sediment‐water interface of rivers often require a lot of information about flow and riverbed characteristics. Unfortunately, this information is often not readily available. We evaluated existing data from flume experiments and the field and added new data from a verified computational model, in order to identify which factors are most important in determining how much solute moves toward the bed at the sediment‐water interface. Using statistical tools, we developed two simple models that require minimal information about the stream and streambed. One model considers sediment size, the other looks at riverbed permeability. We validated these models by comparing them to existing methods and data from other studies, and they performed well. The model based on sediment size, which also reflects the roughness of the riverbed, performs best and is the most user‐friendly because it does not require information about permeability, which is harder to estimate. This model can be further applied for dissolved oxygen transfer and provide a reliable estimate of how oxygen moves at the sediment‐water interface, particularly when specific details about the riverbed are not available. Key Points: We used a validated numerical model to expand the available data set of hyporheic mass exchange under various bed and flow conditionsWe performed reanalysis of flume/field data combined with numerical results to develop models for the hyporheic mass exchange rateWe proposed unifying single‐parameter models for the estimation of hyporheic mass transfer coefficient in open‐channel flows [ABSTRACT FROM AUTHOR]

Hydrogen is gaining attention as a clean energy source for the sustainable development of the global economy and mitigation of global warming. Flow rate measurements are vital for ensuring the accuracy of hydrogen transaction volumes. As a widely accepted standard for gas flow rate, critical flow nozzles are expected to fulfill this role. However, the discharge coefficient associated with the calibration tests of critical flow nozzles for high-pressure hydrogen does not align with the semi-empirical formula of ISO 9300 (ISO curve). This discrepancy has not yet been resolved. In this study, we conducted 3 D numerical simulations of the nozzle discharge coefficients for high-pressure hydrogen. Based on our simulations and experimental results from the previous study, we investigate the cause of the deviation of the discharge coefficient from the ISO curve at high pressure. We also propose a method for calculating the discharge coefficient based on real-gas effects and demonstrate that the discharge coefficient aligns with the ISO curve at high pressures. • High-pressure hydrogen flow is 3D-simulated in critical flow nozzles. • Theoretical mass flow rate of real gases is calculated in high-pressure critical nozzles. • Deviation of nozzle discharge coefficient from ISO curve under high-pressure is explained. • Calculated discharge coefficients of the proposed method match with the ISO curve. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to investigate the effect of shear rate, concentration (4–20 kg/m3) and temperature (20°C–60 °C) on the apparent viscosity of apricot gum solutions. Design/methodology/approach: Apparent viscosity has been measured using a rotational viscometer. Findings: It has been observed that the shear stress and apparent viscosity values increase at high concentrations in the prepared apricot gum solutions. However, it is understood that the higher the temperature in the operation conditions, the lower the apparent viscosity results. Power-law is found the best-fitting model to illustrate the changes in temperature and concentration. According to the consistency coefficient and flow behavior indices, the apricot gum displayed shear-thinning behavior (pseudoplastic). The apricot gum is a polysaccharide with amino and uronic acids, according to Fouirer Transform Infrared Spektrofotometre spectra. Practical implications: The results suggest that power-law model can be used to estimate the viscosity of apricot gum solutions at different temperatures and concentrations for applications for which flow behavior should be taken into account. Originality/value: Exudate gums have good rheological properties and, therefore, are widely used in the food industry. Apricot gum is a biodegradable and abundant polysaccharide that enhances viscosity, stabilizes suspension or emulsion and improves the flow properties of foods. Different rheological models are used to investigate rheological properties. However, those models are time-independent to fit the experimental data. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate the complex three-dimensional vortex structures created by the interaction of gas jet with liquid crossflow. A high-speed camera technique is used to record the evolution patterns of the jet cavity. High-precision numerical methods with the Chorin projection method and volume of fluid method (VOF) are employed to understand the complex flow features associated with jet–freestream interaction. The results present that three distinct regions of the jet cavity could be observed, referred to as the transparent cavity region (TCR), the transition region (TR), and the foam cavity region (FCR). The interaction between the flow of gas jet and liquid crossflow creates multiscale vortex structures, including the counter-rotating vortex pair (CVP), the upper-deck counter-rotating vortex pair (up-CVP), the horseshoe vortices, the shear layer vortices, and the fine-scale vortices, respectively. The relationship between multiscale vortex structures and the pulsation of the gas-liquid interface is analyzed in detail by analyzing the spatial distribution of different vortex structures and the fluctuations of the gas-liquid interface. In addition, the effect of the gas entrainment coefficient on cavity flow patterns and vortex structures is compared and analyzed. • A high-precision numerical simulation method with the Chorin projection method and volume of fluid method (VOF) is established to capture all essential vortex structures for gas jet in liquid crossflow. • The multiscale vortex structures are observed for gas jet in liquid crossflow and the relationships between multiscale vortex structures and gas-liquid interface fluctuation are analyzed in detail. • The discrepancies of the vortex structures and the instability characteristic of the gas-liquid interface at different C Q are analyzed. [ABSTRACT FROM AUTHOR]

Flow fluctuations that are commonly associated with multiphase flow in porous media are studied using concepts from non-equilibrium thermodynamic and statistical mechanics. We investigate how the Green–Kubo formulation of the fluctuation dissipation theorem can be used to predict the transport coefficient from the two-phase extension of Darcy's law. Flow rate-time series data are recorded at the millisecond timescale using a novel experimental setup that allows for the determination of flow fluctuation statistics. By using Green–Kubo relations, a transport coefficient is predicted based on the integrated autocorrelation function. Notably, this coefficient aligned closely with the total effective phase mobility computed using Darcy's equation for multiphase flow, particularly in scenarios where a linear relationship between flow rate and pressure gradient was observed. Our results open a new field of coefficient explorations where microscale fluctuations during multiphase flow are directly linked to macroscale parameters. [ABSTRACT FROM AUTHOR]

Agricultural centrifugal fans play a pivotal role in agricultural machinery, particularly in the context of combine harvesters. The performance of these fans significantly impacts the overall operational efficiency of the machine. Given the absence of robust performance testing and evaluation methodologies for agricultural centrifugal fans, this study assesses fan performance by examining the actual air–flow dynamics in a certain space at its outlet. Subsequently, the effects of various structural parameters on airflow smoothness and attenuation are investigated by computational fluid dynamics simulation analysis. The optimal detection air duct is developed, and the measured fan performance parameters and evaluation indexes are discussed and analysed using bench tests. The obtained results indicate that the arc connection section exhibits reduced interference with the air outlet of the agricultural centrifugal fan. Additionally, the attenuation section, characterised by a diffusion angle of 4°, effectively captures air attenuation properties. Minimal wind speed fluctuation is observed at the measuring point equidistant from the inlet and outlet of the steady flow section. Consequently, optimised structural parameters for the detection air duct and the specified location of the measuring point are determined. Furthermore, the performance parameters of the agricultural centrifugal fan are measured, and dimensional and dimensionless performance evaluation curves are generated based on bench testing. The fan's efficiency increases with higher air volume and flow coefficient but tends to change gradually due to the rate of increase, aligning with the expected performance of the agricultural centrifugal fan. The proposed performance detection device and evaluation method for agricultural cleaning can accurately detect the operational performance of the agricultural centrifugal fan. • A detection air duct for agricultural cleaning fans has been designed. • The variation and attenuation characteristics of airflow in air duct were obtained. • A parameter detection system for agricultural centrifugal fan was developed. • The measured performance parameters of the fan were visualised and evaluated. [ABSTRACT FROM AUTHOR]

Long- and short-range correlations for pairs of charged particles are studied via two-particle angular correlations in pp collisions at s = 13 TeV and p–Pb collisions at s NN = 5.02 TeV. The correlation functions are measured as a function of relative azimuthal angle ∆φ and pseudorapidity separation ∆η for pairs of primary charged particles within the pseudorapidity interval |η| < 0.9 and the transverse-momentum interval 1 < pT< 4 GeV/c. Flow coefficients are extracted for the long-range correlations (1.6 < |∆η| < 1.8) in various high-multiplicity event classes using the low-multiplicity template fit method. The method is used to subtract the enhanced yield of away-side jet fragments in high-multiplicity events. These results show decreasing flow signals toward lower multiplicity events. Furthermore, the flow coefficients for events with hard probes, such as jets or leading particles, do not exhibit any significant changes compared to those obtained from high-multiplicity events without any specific event selection criteria. The results are compared with hydrodynamic-model calculations, and it is found that a better understanding of the initial conditions is necessary to describe the results, particularly for low-multiplicity events. [ABSTRACT FROM AUTHOR]

This paper provides a comprehensive exploration of the operational mechanism of an internal feedback hydrostatic turntable. It employs a self‐compensating gap restrictor mechanism, resulting in heightened load capacity and stiffness. In this paper, the concept of internal flow is innovatively introduced. Subsequently, the Reynolds equation is solved using the finite difference method. This methodology offers a more precise and efficient assessment of the load‐bearing performance of the oil pad within the turntable. Then this paper further investigates the influence of the internal flow coefficient and pressure ratio on oil pad performance, encompassing aspects like load capacity, stiffness, and flow rate. Ultimately, optimal parameters are selected to improve the structure of the gap restrictor, considering various operational scenarios. In conclusion, the method adopted in this study not only improves the calculation accuracy and efficiency but also improves the structure and performance of the oil pad. [ABSTRACT FROM AUTHOR]

• Characteristics of plate evaporator under low heat flux conditions are investigated. • Orifice diameter is the most sensitive to performance compared to orientation and pitch. • Distribution is categorized two profiles and improved at d o = 0.6 mm and φ = -45°. • Superheat oscillation shows high relevant to distribution and performance. • Flow coefficient for distribution pipe design is considered as a constant value of 1.15. Refrigerant distribution among channels plays an important role on performance of plate evaporator, especially under low heat flux conditions. Behaviors of plate evaporator under low heat flux condition are comprehensively and experimentally investigated based on distribution pipe solution in this paper. Influences of orifice diameter d o , orifice pitch d p and injection orientation φ are figured out on overall heat transfer coefficient (HTC), refrigerant distribution, and superheat oscillation. Results show that d o significantly affects evaporator performance compared to d p and φ. The HTC can be improved by 30 % with d o deceasing from 1.0 mm to 0.6 mm. φ obviously influences distribution when d o ≥ 0.7 mm and such effect is diluted at small orifice diameter. Two categories of distribution profiles are observed: rear flooded – front starved shape for the orientation of -45° and rear starved -front flooded shape for -90°. Refrigerant distribution is dramatically improved when d o = 0.6 mm and φ = -45°. Superheat oscillation shows strongly relevant to refrigerant distribution and affects plate evaporator performance distinguishedly. Pressure drop over the orifice is absolutely dominant in total pressure drop of plate evaporator. Flow coefficient of distribution pipe, α is defined and α can be considered as a constant value of 1.15×10−3 for predicting pressure drop and guiding distribution pipe design. The upper and lower deviations between calculated values and test data are within ±8.7 %. [ABSTRACT FROM AUTHOR]

• Experimental flow and heat transfer characteristics of salt solution is carried out. • A simulation model of salt solution ice slurry was proposed based on CFD-PBM. • Flow velocity and ice volume fraction have great influence on flow and heat transfer. As a phase change material, ice slurry allows the storage of thermal energy in the form of latent heat. This has great advantages in terms of reducing energy consumption and environmental protection, and is being widely used. In this study, based on the Eulerian-Eulerian CFD model and the Population Balance Model (PBM), the flow and heat transfer characteristic of salt solution ice slurry was simulation studied, which included the pressure drop, friction coefficient, volume fraction, distribution of ice crystals and local heat transfer coefficient during the flow and solidification of salt solution ice slurry in different conditions. And the experimental system is set up to verify the results of the model and analyze the variation rules of these parameters. The results showed that in salt solutions with different concentrations, when the flow rate and solid phase volume fraction increase, the pressure drop and local heat transfer coefficient of the ice slurry will increase. The surface heat transfer coefficient reached to 2.5 × 103 W m-2 K-1, 2.9 × 103 W m-2 K-1, and 3.2 × 103 W m-2 K-1 when ice crystal volume fraction was 5 %, 10 %, and 15 %, respectively. The study will contribute to understanding of the changes in basic characteristics of salt solution slurry during the flow and phase transition processes. [ABSTRACT FROM AUTHOR]

Clarification of thermal behaviors, involving self-pressurization, temperature rise of the fluid, temperature stratification, and free convective flows, is crucial to the safe storage and transportation of liquid hydrogen for large-scale applications. Given that the experiments have been carried out to observe the pressure build-up and temperature gradient in correlation with part of the thermal behaviors, the computational fluid dynamics method becomes a promising selection for investigating other thermal behaviors to complement the experiments. To comprehensively reveal the thermal behaviors of liquid hydrogen during the no-vented storage process, this paper reviews the progress in both experimental and computational investigations. The typical experimental facilities, conditions, and results of the self-pressurization and temperature stratification in liquid hydrogen tanks are presented. The basic formulations, state-of-the-art applications, as well as typical values of mass transfer coefficients of computational fluid dynamics models are also reviewed. Based on the status, the unclarified effects of vapor-liquid interfacial mass transfer, selection of flow models, and fluid sloshing on thermal behaviors of liquid hydrogen are outlined as the perspectives to benefit future research work. • Experimental investigations on thermal behaviors of LH 2 are summarized. • Progress in the development and applications of CFD studies on thermal behaviors. • Phase change coefficients and the selection of flow models remain unclarified. • Effects of phase change, flow models, and fluid sloshing need further research. [ABSTRACT FROM AUTHOR]

In flow measurement and control industrial application, installing a flow conditioner is an effective way to rectify irregular and unstable flow to stable flow state within a short flow distance. To effectively rectify the eccentric jet flow caused by valve regulation in pipeline, the convergence flow conditioner with convergent orifice angles has been innovatively designed and investigated. However, the effect of structural parameters (such as flow conditioner thickness and flow area) on improving unstable eccentric jet flow rectification was still not elaborated. Thus, the effect of structural parameters of the convergence flow conditioner on rectifying eccentric jet flow was examined in this paper. The structural parameters of the flow conditioner thickness and the flow area were considered under the fixed convergence angle of 12°. The experimental system of monitoring pressures upstream and downstream of the convergence flow conditioner along the pipeline was developed and corresponding numerical simulation was employed. The flow coefficient and resistance coefficient of a convergence flow conditioner under various valve openings were accessed, and monitored pressures along the pipeline were also discussed for numerical simulation verification. The velocity and streamline distributions downstream the convergence flow conditioners were comparatively analyzed. In addition, the axial velocities on various downstream cross-sections were extracted to evaluate the velocity uniformity. A dimensionless parameter of velocity deviation ratio was introduced to quantify the rectification effect of eccentric jet flow evolving in the downstream pipeline. Results showed that the convergence flow conditioner with the thickness of 6 mm and the flow area of 50% owned a better effect on rectifying the valve-induced eccentric jet flow, that is, a shorter flow length was required for changing the valve-induced eccentric unstable flow to uniform stable flow by installing a convergence flow conditioner with above structural parameters. [ABSTRACT FROM AUTHOR]

The impact of raindrops on sheet flow (SF) is a common phenomenon, which plays a vital role in many important nature and engineering fields. The flow resistance of SF is critical for describing flow characteristics and calculating the sediment transport capacity. However, information regarding the theoretical resistance equations of the total resistance of SF subjected to raindrop impact (fr) and the resistance induced by raindrop impact (Δf) is limited. In this study, combination of the π-theorem of dimensional analysis and multiple experimentally simulated rainfalls and inflows was conducted to obtain and verify the deduced predictive flow resistance equations. The results indicated that using dimensionless variables deduced by the π-theorem to calculate the flow resistance equation was appropriate. The main control of fr of SF under rainfall is the ratio of surface roughness to water depth deduced by π-theorem. A newly developed equation [Eq. (24)] can be used to predict fr, with a Nash-Sutcliffe efficiency index (NSE) of 0.91 and a normalized root mean square error (NRMSE) of 0.166. Δf is a very important component to overall SF resistance, accounting for 0.34%–47.79% of fr. The deduced dimensionless variable of the ratio of rainfall intensity to flow velocity is the main controlling factor of Δf. Finally, a new equation [Eq. (26)] was developed to predict Δf, with NSE = 0.673 and NRMSE = 0.445. This study is helpful for understanding the flow resistance subjected to raindrop impact and provides new and scientific equations for flow resistance coefficient prediction. [ABSTRACT FROM AUTHOR]

In this study, the effect of surface vibrations and temperature changes on the heat transfer coefficient of MWCNTs and water nanofluid was evaluated both experimentally and numerically utilizing different concentrations of MWCNTs and water nanofluid. The test results indicate that the application of mechanical vibrations increases the heat transfer coefficient. It has also been observed that the heat transfer coefficient increases with increase in the concentration of nanofluid and fluid temperature. To predict the heat transfer coefficient at any arbitrary combination of the independent variables within the studied ranges, both parametric and non-parametric methods are studied. For the parametric model, the heat transfer coefficient is obtained as a function that is of the first order with respect to flow rate, temperature, and of the second order with respect to nanofluid concentration and vibration amplitude. The robust least square algorithm is used to find the predictors of the parametric model. Also as a non-parametric study, a two-layer feed-forward artificial neural network is used to predict the heat transfer coefficient. The results show that the generalization of the both models is acceptable for non-trained datasets; nevertheless, the prediction error of the parametric model is higher than the non-parametric one, especially for high values of the vibration amplitudes. [ABSTRACT FROM AUTHOR]

The volume of inbound passenger flow at urban rail stations during peak hours is often excessive, which poses potential safety hazards to passengers. In addition, it also reduces the fairness of passenger services at the various stations and leads to inconvenience in the operation of these stations. Therefore, a nonlinear multi-objective planning model with the constraints of the maximum passenger density in the waiting area, the maximum section carrying capacity, and the passenger flow control coefficients are established to find the optimal flow control scheme. The model aims to minimize the variance of the average passenger dwell time and the count of lost passengers at all stations of the line. A hybrid simulated annealing particle swarm optimization algorithm (SA-PSO) is designed to solve the model. The up direction of Shenzhen Urban Mass Transit Line 4 is adopted here as an example for research. The research results indicate that the optimal passenger flow control scheme can effectively reduce the sum of lost passengers and maintain passenger density within the safety range in all waiting areas at each station. Additionally, it is observed that under the optimal passenger flow control scheme, the average dwell time of all stations is more balanced. Overall, the optimized flow control scheme is more effective in coping with large urban rail passenger flows than several no flow control and non-optimized flow control schemes. [ABSTRACT FROM AUTHOR]

• Developed XGBoost model to predict refrigerant mass flow through electronic expansion valves. • Achieved improved prediction accuracy over existing models using two refrigerants. • XGBoost effectively captured complex nonlinear flow dynamics with 96.4–90.6 % accuracy. • A low RMSE of 2.2–4.23 % indicated high predictive performance of the developed model. • Advanced machine learning approach provides direction for more efficient refrigeration control. In an effort to enhance the prediction accuracy of the mass flow characteristics of refrigerants through electronic expansion valves (EEVs), this study develops a mass flow model using the XGBoost machine learning algorithm. Utilizing experimental data from open literature for refrigerants R1233zd(E) and R245fa, the model aims to accurately predict the mass flow coefficient in EEVs, a crucial aspect for improving the performance and efficiency of refrigeration systems. The model's performance is evaluated using the coefficient of determination (R2) on the training and test datasets, revealing a minimal performance gap and no overfitting issue. Remarkably, our model's predictions for R1233zd(E) and R245fa datasets align consistently with experimental data, with 96.4 % and 90.6 % of the predicted data deviating from the experimental ones within ±5 %, respectively. Further, the root-mean-square error (RMSE) and coefficient of variation of the root mean square error (CV-RMSE) values are quite low, with 2.2 % and 2.33 % for R1233zd(E), and 4.23 % and 4.47 % for R245fa, indicating high prediction accuracy. Compared to the original models, the paper approach with the XGBoost algorithm significantly improves prediction accuracy. This advancement provides a promising direction for developing more efficient and reliable control strategies for refrigeration systems in various applications. [ABSTRACT FROM AUTHOR]

A well-designed flow channel is crucial for effective water management in proton exchange membrane fuel cell. This study presents novel simulation investigation of the dynamic behavior of liquid water in three-dimensional multi-channels with various shape designs, including straight channel (SC), blocked channel (BC), wave channel (WC), and tapered channel (TC). The first, second, and third single channels are arranged in order from gas inlet in multi-channel. The results indicate that drainage rate of first channel in multi-channel is slower than that of second and third channel. Among the four designs, BC and TC reduced water ejection time by 7 ms and 6.5 ms respectively compared to SC, and reduced the time by 39 ms and 38.5 ms respectively compared to WC. In base case, drag reduction rate of TC compared to BC and WC increased by 4.12% and 20.98% respectively. However, WC has the smallest water coverage and average drag reduction ratio, while SC has a lower average gas flow resistance coefficient. This research offers innovative perspectives and theoretical foundations for current flow field design. • Dynamic behavior of liquid water in multi-channels with varying shapes is studied. • The average inlet velocity gradually increases from the first to the third channel. • The blocked channel and tapered channel exhibit better drainage performance. • Wave multi-channel demonstrates lowest water coverage and drag reduction ratio. • Straight multi-channel presents the lowest average flow resistance coefficient. [ABSTRACT FROM AUTHOR]

Coral sandy soils widely exist in coral island reefs and seashores in tropical and subtropical regions. Due to the unique marine depositional environment of coral sandy soils, the engineering characteristics and responses of these soils subjected to monotonic and cyclic loadings have been a subject of intense interest among the geotechnical and earthquake engineering communities. This paper critically reviews the progress of experimental investigations on the undrained behavior of coral sandy soils under monotonic and cyclic loadings over the last three decades. The focus of coverage includes the contractive-dilative behavior, the pattern of excess pore-water pressure (EPWP) generation and the liquefaction mechanism and liquefaction resistance, the small-strain shear modulus and strain-dependent shear modulus and damping, the cyclic softening feature, and the anisotropic characteristics of undrained responses of saturated coral sandy soils. In particular, the advances made in the past decades are reviewed from the following aspects: (1) the characterization of factors that impact the mechanism and patterns of EPWP build-up; (2) the identification of liquefaction triggering in terms of the apparent viscosity and the average flow coefficient; (3) the establishment of the invariable form of strain-based, stress-based, or energy-based EPWP ratio formulas and the unique relationship between the new proxy of liquefaction resistance and the number of cycles required to reach liquefaction; (4) the establishment of the invariable form of the predictive formulas of small strain modulus and strain-dependent shear modulus; and (5) the investigation on the effects of stress-induced anisotropy on liquefaction susceptibility and dynamic deformation characteristics. Insights gained through the critical review of these advances in the past decades offer a perspective for future research to further resolve the fundamental issues concerning the liquefaction mechanism and responses of coral sandy sites subjected to cyclic loadings associated with seismic events in marine environments. [ABSTRACT FROM AUTHOR]

Dynamically loaded soils can exhibit large-deformation flow liquefaction or limited-deformation cyclic mobility mechanisms, depending on the initial state of the soil. Undrained cyclic triaxial tests were performed on saturated calcareous and silica sand specimens prepared with different relative densities and subjected to various effective confining pressures and cyclic stress ratios to study the flowability of viscous liquefied sand. The cyclic shear stress–strain rate relationship for calcareous and silica sands transitioned from an elliptical shape to an asymmetric Lamé curve shape as excess pore pressures accumulated under cyclic loading. The asymmetric Lamé curve–shaped relationship demonstrates that the saturated sand exhibited low shearing resistance and high fluidity under elevated excess pore pressures for the conditions evaluated. The average flow coefficient, κ¯ , defined as the maximum shear strain rate triggered by the unit average cyclic shear stress, and the flow curve defining the variation in κ¯ with the number of loading cycles, describes the flowability of the saturated sand and is used to quantify the cyclic failure potential of the saturated sand under a proposed viscous fluid flow failure criterion. The effect of relative density, effective confining pressure, and cyclic stress ratio on the flow curves and the number of cycles to failure under the proposed viscous fluid flow failure criterion is discussed and compared with the cyclic resistance determined from widely used excess pore pressure– and strain-based cyclic failure criteria. The viscous fluid flow cyclic failure criterion is more stringent than these alternative criteria, and the corresponding axial strains are consistent with those associated with liquefaction triggering under cyclic strain approach. [ABSTRACT FROM AUTHOR]

Wing smarting and eliminating conventional control surfaces are fundamental parameters for improving aircraft aerodynamic performance in future aviation. Twist is a well-known tool that, along with the development of morphing technology, can play a crucial role in controlling next-generation aircraft. However, wing twisting with a control approach requires many aerodynamic studies, particularly at the high aft-swept angle; this is more noticeable in the flying wing configuration. In this paper, a control strategy based on twist morphing has been evaluated aerodynamically at the Swing, a flying wing configuration. Extraction of aerodynamic coefficients and flow field on the wing have been performed using the computational fluid dynamics (CFD) method in an incompressible flight regime. To comprehensively cover the control needs, two control concepts have been introduced, called independent and nonindependent twist. Within the concept of independent twist, a co-oriented twist arrangement (Co-OTA) and counteroriented twist arrangement (Cun-OTA) are applied to the wings, which are used to produce pitching and rolling moments, respectively. The results show these control arrangements have high efficiency at low angles of attack (AoAs), but as the AOA increases, their aerodynamic performance will gradually decrease. In this regard, a significant challenge for Cun-OTA is producing the yawing moment during roll maneuvering. Attempts to solve this problem have led to the idea of a compound twist arrangement (CTA). The existence of a control arrangement to generate yawing moment is beyond the capacity of the independent twist concept. The nonindependent twist has been introduced as a solution to this issue. Conventional control surfaces have various weaknesses, one of the most important of which is the unfavorable effects on aerodynamic efficiency; the reduction of aerodynamic efficiency leads to a drop in flight endurance and an increase in fuel consumption. At a step forward, with the approach of wing smarting and morphing technology, the tasks of conventional control surfaces can be delegated to the wing itself. Therefore, it will be possible to remove the control surfaces and integrate the wing. In this article, according to the mentioned approach, an attempt was made to introduce a control strategy based on the geometric twist. In this strategy, the value and direction of the twist applied to each wing produces a specific control arrangement. Control arrangements (three types of arrangements) are involved in producing longitudinal and lateral and modified lateral moments. The results indicate that the use of twisting in aircraft control is efficient for a wide range of flight conditions, and this capability exists to be used in the next generation of aircraft. In this way of control, challenges are deliberately related to the design of the operating mechanism, safety issues, and weight. [ABSTRACT FROM AUTHOR]

The elliptical hole has the potential to promote jet breakup and improve atomization and mixing quality. The flow behavior in the nozzle and the outflow characteristics have an important influence on the atomization and mixing process of the downstream fuel. Therefore, the inner cavitation flow processes and outflow characteristics for elliptical holes for scramjet engine at injection pressures of 3 MPa and 5 MPa were investigated using the Volume of Fluid (VOF) method and Large Eddy Simulation (LES). The numerical findings demonstrated that the cavitation region and vortex structures of elliptical holes mainly appeared on the long axial plane. The cavitation intensity of elliptical holes was weaker than that of the circular hole. Compared with the circular hole, the gas phase volume fraction of elliptical hole with the aspect ratio of 4 was reduced by about 22.1 and 21.1% respectively under 3MPa and 5MPa injection pressure. The application of elliptical holes inhibited the generation of cavitation and had large mass flow rate and flow coefficient. The mass flow rate of the elliptical hole with the aspect ratio of 4 was the largest, and the mass flow rate increased by about 5.1% compared with that of the circular hole. Elliptical holes showed a smaller velocity coefficient and a larger area coefficient when cavitation existed. The elliptical hole with the aspect ratio of 4 held the smallest velocity coefficient and largest area coefficient, with the difference of 12.1% and 18.9% respectively from the circular hole. Another important point was that elliptical holes enhanced the turbulent disturbance at the hole outlet, which facilitated the breakup of downstream jet. [ABSTRACT FROM AUTHOR]

One of the challenges in using Manning’s equation lies in accurately determining Manning’s roughness coefficient, especially due to sediment transport. The condition of sediment transport within a specific section of a river can be in equilibrium, meaning that the amount of sediment entering and exiting the segment is balanced or it can be in non-equilibrium, where there is an imbalance between the sediment entering and leaving the segment. Experiments were carried out in the laboratory to simulate both transport conditions, one involving sediment feeding (equilibrium condition) and the other without sediment feeding (non-equilibrium condition). A total of 180 mean velocity profiles were measured using an acoustic doppler velocimeter (ADV) in fixed and movable bed flows. The present experiment was combined with theoretical approaches to evaluate Manning’s coefficient in open channels under sediment transport-flow conditions and reach conclusive results. The shape of the velocity profile, u/U, for flows over a movable bed with sediment feeding is “slender” compared to those without sediment feeding. The presence of sediment transport affects the shape of the velocity profile, especially in the inner region, influencing Manning's roughness coefficient. This coefficient can be determined from two-point velocity measurements at z/H = 0.1 and 0.2 for fixed and movable bed flows with and without sediment feeding, respectively. On average, sediment feeding increases the coefficient by 19% compared to the non-sediment feeding case. [ABSTRACT FROM AUTHOR]

Weirs of the labyrinth have some advantages including the high coefficient of the irrigation of weir and the low fluctuation of water when the flow passes over the crest of the weir. In this research, the flow rate coefficient has been investigated by changing the weir geometry in terms of wall slope, arc cycle angle, and nose length change in the upstream and downstream of each cycle of the trapezoidal arc labyrinth weir. A total of 240 tests have been performed on 16 different physical models in a channel with a width of 120 cm and a narrowing of 20 cm from each wall. All models have been compared with the control model (normal labyrinth weir) (80A). The results showed that the 80B weir with an arc cycle angle of 20 degrees and without wall slope has a better performance than other weirs. Also, the weir with an arc cycle angle and a wall slope of 20 degrees in a divergent form (D20B) in the area (Ht/P) <0.31 has a better performance than other weirs with an arc cycle angle of 20 degrees, and after this area, the weir with a wall slope of 10 degrees has performed better in divergent form (D10B). In weirs with different cycles at an arc cycle angle of 20 degrees, the labyrinth weir with 5 cycles (N5) has performed better up to the point (Ht/P)=0.36. Also, at the maximum point, the difference is 13 and 17%, respectively, compared to the 4-cycle and 3-cycle weirs. [ABSTRACT FROM AUTHOR]

Liquid hydrogen has attracted widespread attention due to industrial decarbonization as an excellent carrier of renewable energy accommodation. Accurate prediction of the heat transfer coefficient during flow boiling has become a fundamental prerequisite for enhancing the design rationality and safety of hydrogen devices since a slight heat leak will trigger flow boiling. A novel selection standard of the dataset for liquid hydrogen flow boiling is proposed, and an experimental database of liquid hydrogen is compiled, including 923 data points from 5 sources. The prediction performance of eight conventional empirical correlations and six machine learning models for liquid hydrogen flow boiling is compared and evaluated. Results show that the prediction ability of machine learning models for the heat transfer coefficient of liquid hydrogen flow boiling is much higher than that of traditional correlations. Fang correlation is recommended to use as the calculation benchmark due to simplicity and reliability if the inlet condition is obscure. The Extra tree model shows the most excellent evaluating performance among the six machine learning models with a mean absolute deviation of 11.44% and a fairly superior R 2 of 0.9543. The Froude number Fr exhibits an essential impact according to the feature importance analysis, which may need to be taken into account when developing new empirical correlations. An improved correlation for the flow boiling of liquid hydrogen is provided based on the Fang correlation, achieving a mean absolute deviation of 18.61% and a mean relative deviation of 16.49%. The results of this paper can offer some theoretical guidance for the design of a liquid hydrogen apparatus. [Display omitted] • A novel selection standard of data set for liquid hydrogen flow boiling is proposed. • Fang correlation is recommended as the calculation benchmark due to simplicity and reliability. • Extra tree model has the best prediction performance with MAD of 11.44% and R 2 of 0.9543. • Froude number Fr exhibits an essential impact on heat transfer. • An improved correlation is proposed with MAD of 18.61% and MRD of 16.49%. [ABSTRACT FROM AUTHOR]

We explored here the case of three-dimensional non-stationary flows of helical type for the incompressible couple stress fluid with given Bernoulli-function in the whole space (the Cauchy problem). In our presentation, the case of non-stationary helical flows with constant coefficient of proportionality α between velocity and the curl field of flow is investigated. In the given analysis for this given type of couple stress fluid flows, an absolutely novel class of exact solutions in theoretical hydrodynamics is illuminated. Conditions for the existence of the exact solution for the aforementioned type of flows were obtained, for which non-stationary helical flow with invariant Bernoulli-function satisfying to the Laplace equation was considered. The spatial and time-dependent parts of the pressure field of the fluid flow should be determined via Bernoulli-function if components of the velocity of the flow are already obtained. Analytical and numerical findings are outlined, including outstanding graphical presentations of various types of constructed solutions, in order to elucidate dynamic snapshots that show the timely development of the topological behavior of said solutions. [ABSTRACT FROM AUTHOR]

In this paper, the collective motion of viscous drops is investigated in terms of a porous medium setting. We assume that the interface of each of the drops is fully covered with a stagnant layer of surfactant in an arbitrary unsteady Stokes flow with low surface Péclet number limit. The effect of the interfacial slip coefficient on the behavior of the flow fields is also considered. The modeling of the physical processes leads to a system of parabolic partial differential equations (PDEs) with interfacial boundary conditions. We have proposed a model in a micro--macro scale setting. We have shown the existence of a unique positive weak solution of such system. We have also obtained a homogenized (upscaled) model of the system via two-scale convergence and boundary unfolding method. [ABSTRACT FROM AUTHOR]

We establish sharp relations between several regularity coefficients for flows generated by non-autonomous differential equations. We verify that these relations are sharp by showing that all possible values of the regularity coefficients satisfying these relations are attained by some linear equation with bounded piecewise-continuous coefficient matrix. In addition, we introduce two new regularity coefficients and we obtain sharp relations between these and other coefficients. [ABSTRACT FROM AUTHOR]

The forward-curved multi-blade centrifugal fan is widely used in the ventilation and household appliance industries with limited space due to its small size factor, high pressure coefficient, and large outlet flow coefficient. Conventional centrifugal fan structural designs rely on empirical data, resulting in drawbacks during usage such as low airflow velocity, high noise levels, and high energy consumption. In order to optimize fan structure, enhance aerodynamic performance, and seek new, effective approaches for energy efficiency and emissions reduction, this paper focuses on a combined design method that integrates scroll line design with aerodynamic performance and noise control. The goal is to propose a noise prediction and analysis method for multi-blade centrifugal fans, addressing the design contradiction between optimal fan functionality and minimal noise within limited design dimensions. The dynamic radial basis function method is introduced to investigate the geometric parameters of the scroll line, utilizing coherence analysis to identify the reasons for insufficient aerodynamic performance and noise reduction measures. Through the research, it is found that unreasonable design leads to a large turbulent vortex region within the blade passage and internal flow field, particularly involving circulation and backflow, which significantly reduces the fan's aerodynamic performance and operational efficiency. The design incorporates a composite scroll with a logarithmic spiral and circular arc integrated into one, and algorithm-based optimization of the scroll tongue, facilitating the transition of turbulence at the scroll outlet and the gap between the scroll tongue and impeller. Numerical results show an increase in airflow of 3.04 m3/min and a noise reduction of 3.79%. This indicates that the composite scroll design with a logarithmic spiral plays a dominant role in accelerating the aerodynamic performance of the scroll and reducing noise radiation. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation of the flow pattern regime and unsteady characteristics of ventilated cavities with different headform shapes. The test model consists of a removable headform with three different forebodies (the conical, the blunt, and the hemispherical) and a common cylinder rear body. Experiments are conducted in a closed-loop cavitation tunnel. First, the flow pattern regimes on the ventilated cavity for different headforms are discussed in detail, and the dimensions of several flow patterns are measured. The results show that the cavity dimension and the regime are strongly dependent on the headform shape, and all typical flow patterns are introduced by schematic illustrations. Second, the ventilation hysteresis that happened during the flow pattern transition is pointed out. A quantitative gas leakage model is employed to explain the cause of hysteresis and flow pattern transition, and the results show the Strouhal number for different headforms is approximately ∼0.21. However, the blunt presented stronger gas leakage with a large constant parameter, K = 0.80. Finally, the unsteady characteristics of the ventilated cavity around different tested headforms are involved through descriptions of developments of the recirculating vortex and transparent cavity. In addition, an estimated cavitation number is applied to investigate the unsteady characteristics, and the maximum cavitation number and the strongest characteristic are obtained by the blunt headform due to the large drag coefficient and strong flow separation. [ABSTRACT FROM AUTHOR]

The trace of the polymer conformation tensor in numerical simulations is bounded by applying a logarithmic transformation to the elastic force in the finitely extensible nonlinear elastic-Peterlin model. This method, called elastic stress logarithmic transformation (EL), is combined with the artificial diffusion (AD) and square-root conformation reformulation (SRCR) methods to establish EL-AD and EL-SRCR methods, respectively. The accuracy and stability of these methods have been investigated by conducting direct numerical simulations of viscoelastic laminar flows around a circular cylinder at a Reynolds number Re = 100, considering a wide range of rheological parameters: the maximum polymer extensibility L = 10 and 100, and the Weissenberg number W i = 1 − 80. Specifically, effects of artificial diffusion coefficients measured by dimensionless Schmidt number S c c = 10 − 10 6 on the flow are studied. The results indicate that the EL method can effectively ensure the boundedness and accuracy of the conformation tensor trace, making the EL-AD method a valuable modification of the AD method for simulations with larger L and Wi. The impact of the polymer stress diffusion on the simulation is complex. It can stabilize the simulation by reducing sharp gradients and peak positions of elastic stress. However, inappropriate artificial diffusion coefficients lead to flow artifacts when L is large (L = 100). One consequence is an amplification of the solid-like phenomenon caused by polymer near the upstream stagnation point of the cylinder. Another consequence is an enhanced suppression of vortices by polymer downstream of the cylinder. The challenge in determining a suitable AD coefficient emphasizes the superiority of the EL-SRCR method in terms of stability and accuracy. [ABSTRACT FROM AUTHOR]

The Chiral Magnetic Wave (CMW) phenomenon is essential to provide insights into the strong interaction in QCD, the properties of the quark-gluon plasma, and the topological characteristics of the early universe, offering a deeper understanding of fundamental physics in high-energy collisions. Measurements of the charge-dependent anisotropic flow coefficients are studied in Pb-Pb collisions at center-of-mass energy per nucleon-nucleon collision s NN = 5.02 TeV to probe the CMW. In particular, the slope of the normalized difference in elliptic (v2) and triangular (v3) flow coefficients of positively and negatively charged particles as a function of their event-wise normalized number difference, is reported for inclusive and identified particles. The slope r 3 Norm is found to be larger than zero and to have a magnitude similar to r 2 Norm , thus pointing to a large background contribution for these measurements. Furthermore, r 2 Norm can be described by a blast wave model calculation that incorporates local charge conservation. In addition, using the event shape engineering technique yields a fraction of CMW (fCMW) contribution to this measurement which is compatible with zero. This measurement provides the very first upper limit for fCMW, and in the 10–60% centrality interval it is found to be 26% (38%) at 95% (99.7%) confidence level. [ABSTRACT FROM AUTHOR]

We show that if drift coefficients of Arratia flows converge in L 1 (R) or L ∞ (R) then the 1-point densities associated with these flows converge to the density for the flow with the limit drift. The main result is proven by providing a representation of the probability of coalescence in the flow as a solution to a PDE and applying the perturbation theory. [ABSTRACT FROM AUTHOR]

We present a review of published experimental measurements on anisotropic flow in heavy-ion collisions. Flow coefficients v n are presented for charged and identified hadrons at various beam energies ranging from s NN = 7. 7 GeV to 200 GeV at the Relativistic Heavy Ion Collider (RHIC) and s NN = 2 7 6 0 GeV at the Large Hadron Collider (LHC). We present v 1 and its slope d v 1 ∕ d y and discuss possible first-order Quantum chromodynamics (QCD) phase transition. v 1 of particles containing heavy quarks (Charm quarks) is also discussed to illustrate the effect of the magnetic field produced in relativistic heavy-ion collisions. We also present flow harmonics ( v 2 , v 3 and v 4 ) for inclusive charged and identified hadrons. We compare the charged particle v n coefficients with hydrodynamics to study and constrain initial conditions in the transport models. The results of identified particle v 2 from ideal and viscous hydrodynamics are discussed to understand the dynamics and mechanism of particle production in high-energy nuclear collisions. [ABSTRACT FROM AUTHOR]

Multi-way spool valves (MWSVs) with K-shape notches (KSNs) provide advantages such as improvement of the actuator speed control, micro-action, and response performance. However, the pressure drop (PD) associated with the energy consumption is larger of MWSVs under the high-pressure and large-flow condition. Meanwhile, extremely complex flow coefficient and multi-parameter, highly coupled KSNs are the chief factors restricting the flow-pressure characteristics exploration and optimisation design of MWSVs. To address these problems, complete numerical research and experiment are performed in this study, especially concerning the method of MWSV flow-pressure characteristics modelling, and surrogated model-based optimal design of KSN structures. First, the relationships between KSN structure parameters and flow-pressure properties of MWSV are modelled on the innovative discharge area parameter model (DAPM) and response surface methodology (RSM) (RSMDPAM) using the CFD dataset. Second, to reduce the PD combining the flow control performance, surrogate model-based optimisation design is addressed. During optimisation, six KSN structure parameters are chosen as design variables, PD and flow area relative deviation (FARD) are selected as objective functions, and the RSM is employed as the projected model. Depended on the created surrogate model, the non-dominated sorting genetic algorithm (NSGA-II) is established to search for the optimal KSN structure. To certify the performance of the optimisation, flow field characteristics are analysed. The results demonstrate that the proposed RSM-DAPM-RSM model achieves reliable prediction for PD and FARD with a great correlation coefficient (0.9757 and 0.9946). The average PD reduces as much as 7.23% while the FARD is only 1.28%. Moreover, the region of low-pressure, highvelocity, and high-turbulent kinetic energy in the flow field are reduced. The proposed framework enhances the performance in KSN spool optimisation and could be applied to other kinds of notches. [ABSTRACT FROM AUTHOR]