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Hybrid nanofluids provide several advantages over conventional fluids, including improved thermal characteristics, increased stability, customizable features, multifunctionality, and environmental advantages. Hybrid nanofluids are an appealing alternative for a variety of applications due to these benefits. This study aims to compute the non-similar solution of single-multi wall carbon nanotubes (SWCNTs-MWCNTs)-based hybrid nanofluid flow over an inclined extending surface. Heat transmission and flow are observed under the effects of quadratic convection, Darcy-Forchheimer quadratic drag forces, viscous dissipation, and non-linear thermal radiative heat flux. The velocity and thermal slip constraints are imposed at the inclined surface. For the model-based comparison, Xue, and Modified Hamilton Crosser thermal conductivity models for carbon nanotubes (CNTs) are adopted. The irreversibility of the system is also investigated using the second law of thermodynamics for the distinct CNTs-based thermal conductivity models. Non-similarity variables are adopted to convert nonlinear partial differential equations into dimensionless PDEs. Analytical modeling of non-similar systems is done by adopting non-similarity transformations up to second-level truncation, and the bvp4c technique is then used to compute the results numerically. The research found that at 75° of plate inclination, the Modified Hamilton Crosser model for CNTs outperforms the Xue model in terms of heat transfer rate. Further, entropy generation is significantly larger for the Xue model than for the Modified Hamilton Crosser model for CNTs against higher values of viscous dissipation and porosity parameters. It is also revealed that for opposing buoyancy force GR < 0, the temperature of the fluid escalates. This study possesses multiple applications including petroleum engineering, heat exchangers, environmental remediation, and biomedical applications. [ABSTRACT FROM AUTHOR]

In mineral processing, column flotation is being used extensively for fine particle beneficiation. Although a few attempts were made to develop computational fluid dynamics (CFD) models for column flotation in the past, validation against comprehensive experimental data is yet to be demonstrated. This work employs an Eulerian-Eulerian model coupled with the standard k-ε turbulence model for modeling the hydrodynamics in the column flotation. The two-phase simulations were performed on both laboratory and industrial-scale column flotations. The two-fluid model was further modified with the appropriate interphase forces (Ishii-Zuber drag force and Tomiyama lift force) and population balance method (PBM) to accurately simulate and predict the bubble dynamics. The axial and radial gas holdup variations along with the axial liquid velocity are predicted at different air and liquid superficial velocities. The numerical predictions were then validated against the Electrical Resistance Tomography (ERT) data in a 4-inch laboratory column flotation and conductivity probe data in an industrial column flotation. The modified two-fluid model was able to predict accurate hydrodynamics close to ERT data. The gas holdup was found to increase with the superficial air velocity, liquid height, and liquid velocity. The gas holdup found uniformly dispersed radially at low superficial air velocities and heterogenous dispersed bubble flow at higher superficial velocities. A parabolic profile of liquid flow observed at higher superficial air velocities. [ABSTRACT FROM AUTHOR]

Recent advancements in nanofluid technology have emphasized the potential of ternary hybrid nanofluids (THNFs) to significantly enhance thermal and hydrodynamic properties. The implementation of a wavy sinusoidal cylinder is proposed as a novel approach to optimize heat transfer in a variety of engineering applications. This study focuses on analysing the flow and thermal behaviour of TiO2-Al2O3-MoS2/Kerosene oil a THNF around a circular cylinder with a sinusoidal radius, demonstrating enhanced heat conduction capabilities compared to conventional hybrid nanofluids. The governing equations, formulated as partial differential equations, are solved using the bvp4c solver. The study reveals that the shape of nanoparticles plays a crucial role in heat transfer efficiency. Specifically, when the solid volume fraction increases from 1% to 3%, brick-shaped particles exhibit the lowest heat transfer enhancement of 25.80%, while blade-shaped particles achieve the highest enhancement of 68.24%. Additionally, the heat transfer coefficient improves from 1.5% to 1.8% across different nanoparticle shapes under varying dissipation parameters. Similar trends are observed in the reduction of drag force with changes in the velocity slip parameter. These findings underscore the significant impact of nanoparticle shape and volume fraction on the thermal performance of THNFs, offering valuable insights for optimizing heat transfer systems in engineering applications. [ABSTRACT FROM AUTHOR]

This paper investigates the two-phase flow hydrodynamics of a column flotation operated from a homogeneous to a heterogeneous flow regimes using experimental and computational fluid dynamics (CFD) techniques. Experiments were conducted in a lab scale column flotation of 0.1 m internal diameter and 2.5 m length at various superficial gas velocities using a dual plane electrical resistance tomography (ERT). The mean gas holdup increased from 2 to 18% with the increase in superficial gas velocity from 0.6 to 7.2 cm/s. The gas holdup-based bubble swarm velocity method identified four distinct flow regimes, i.e. homogeneous bubbling regime, narrow discrete bubbling regime, a sustained helical flow regime and churn turbulent flow regime in the column. Further, transient simulations were conducted using a two-fluid model coupled with a population balance model to assess the flow behavior inside the column. Virtual mass, lift and drag forces were incorporated into the model to account for the interphase forces. Numerical simulations predicted mean gas holdup was matching with the experimental data at low gas velocities (<2.4 cm/s), and a marginal deviation was noted at higher gas velocities (>2.4 cm/s). The predicted radial gas holdup profiles were found to change from flatter to parabolic with the increase in gas velocities, i.e. similar to the experiments. The effect of particle size on the rate constant and recovery was estimated with Luttrell and Yoon’s performance model using the particle floatability input data and the two-phase experimental data. The developed CFD model can be useful to optimize the operating and design parameters for efficient operation of the column flotation process. [ABSTRACT FROM AUTHOR]

In this article, the test particle method is used in order to calculate the Cherenkov radiation of runaway electrons. We have applied the dielectric tensor for hot magnetized plasma to derive the wave frequency of Cherenkov radiation due to particle resonance with the warm electrostatic waves. The electric field from the Cherenkov radiation is numerically calculated to model the radiation reaction force as a correction to the Coulomb logarithm in the collisional drag force. Then, the behavior of the correction term in strongly and weakly magnetized regimes is investigated. It is shown that both magnetic field strength and the speed of runaway electrons significantly modify the correction term. [ABSTRACT FROM AUTHOR]

When the high-speed elevator is running, the air in the hoistway is rapidly compressed and released to form the piston effect. Especially when the car and counterweight intersect, the piston effect makes the aerodynamic force of the car and counterweight change sharply, affecting the stability of elevator operation. In this study, a three-dimensional car counterweight intersection model is constructed, and a multi-region dynamic layered method is proposed to calculate the aerodynamic flow field in the whole moving process, the changes of aerodynamic drag force and aerodynamic lateral force of the car and the counterweight under different length ratio, blockage ratio and spacing are analyzed and simulated, and the influence of structural changes in the hoistway on the aerodynamic flow field is studied. Furthermore, the accuracy of the numerical results is verified by the real elevator test. Finally, the results show that when the car intersects the counterweight in the hoistway, the interaction between the car and the counterweight is enhanced, and the drag force coefficient and lateral force coefficient of the car suddenly change, and return to the normal state after the intersection, with the decrease of length ratio and spacing and the increase of blockage ratio, the sudden change degree of drag force also increases, and the sudden change of lateral force of the car is mainly affected by the car counterweight spacing, and increases with the decrease of spacing. [ABSTRACT FROM AUTHOR]

Flow over an Iranian bridge deck is studied under an actual extreme flood event happening similarly nowadays in many countries due to climate change. Rigorous transient fluid-structure interaction analyses using the realizable k-ε turbulence model and the VOF Method are conducted. Geotechnical and abutments damages are neglected. Water surface profiles, velocity vectors, and hydrodynamic coefficients are determined. Based on the latest hydrological regime, particularly in supercritical flows, the results are partially compared against the latest advanced design codes, to evaluate the performance of their hydrodynamic and hydraulic provisions in similar incidents. It was acknowledged that the flood loads recommended by the Federal Highway Administration (FHWA) are fairly acceptable, Eurocode-1 predicts them rather accurately but not in extreme cases, and the Australian Standard (AS-5100.2) is less effective due to over-estimation of the hydrodynamic loads. Instead, the latter offers comprehensive user-defined hydraulic conditions. Furthermore, upon gradual rise of the water level to thrice the deck height, bridge stability is found to be at risk due to highly turbulent states. It is recommended that due to such threats, re-evaluation of flood regime, as well as its distinct hydrodynamic properties have to be accounted for, when evaluating existing bridges or designing new ones. [ABSTRACT FROM AUTHOR]

This study explores the impact of end electric current on the performance of a marine magnetohydrodynamic (MHD) propulsion motor or thruster using a comprehensive 3D numerical simulation. The investigation focuses on various operating parameters, such as electromagnetic and drag forces, efficiency, losses, current, and different pressure components. To validate the numerical findings, a scaled-down experimental setup is utilised. The results demonstrate that certain operating parameters of MHD motors are not affected by the three-dimensional characteristics of their channels. These parameters, including fluid velocity, can be accurately calculated using the analytical model based on the effective electric current of the motor. Conversely, other operating parameters of MHD motors are significantly influenced by the end effects in their channels. For example, the overall efficiency, which depends on the total electric current of the motor, should be calculated using a more precise simulation method. [ABSTRACT FROM AUTHOR]

The use of hybrid nanoparticles instead of nano solid-particles is one of the most serious tasks to improve the heat transport of fluids in drilling to recovery oil. This article is to analyze the heat transport of MHD radiative Carreau hybrid nanofluid, consisting of SiO2–Fe3O4 in an equal ratio base fluid of polyethylene glycol-H2O with heat source and a viscosity variation. The PDEs system that controls the problem was resolved by a numerical method after transformation into ODEs. [PEG + H2O/SiO2]m and [PEG + H2O/SiO2+Fe3O4]h thin films are fabricated by using spin coating technique with a thickener of 150 ± 5 nm/25°C. The most notable findings of this analysis include the influence of the velocity, temperature outlines, drag force factor, and local Nusselt number of different variable parameters. The results specifically determine that $ \mathrm{\Delta }E_g^{Opt} $ Δ E g Opt amount declines from 4.894 eV for [PEG + H2O/SiO2]m mono nanofluid to 1.969 eV for [PEG + H2O/SiO2+Fe3O4]h hybrid nanofluid utilizing DFT calculations HOMO and LUMO calculation. The results decide that the [PEG + H2O/SiO2]m is transmuted from semi-conductor to [PEG + H2O/SiO2+ Fe3O4]h as a super-conductor with adding [Fe3O4]NPs. The hybrid nanoparticles have a higher influence than nanoparticles on the velocity distributions. [ABSTRACT FROM AUTHOR]

Magneto-thermomechanical applications range from magnetic resonance imaging to electric diodes and the design of dielectric grease. To contribute significantly to the biomedical industry for proper prediction and treatment of diseases such as cancer, stenosis, and technological advancement in the design of electronic tools. This study presents the significance of magneto-thermomechanical modeling of Reiner–Philippoff fluid flow subject to thermal radiation influence. The Reiner–Philippoff fluid encapsulates the properties of shear-thinning, shear-thickening, and Newtonian fluids in different viscosity regimes. The main-stream velocity ue is considered in its generalized form as well as taking into account the influence of thermal radiation and thermal conductivity. To obtain the computational model analysis, a numerical tool via the bivariate spectral collocation method is deployed on the resulting transformed PDEs. Upon validation of the method, the profile distributions of respective boundary layers with respect to the Bingham number, magneto-thermomechanical parameter, and Reiner–Philippoff fluid parameter are analyzed and discussed. The results of the engineering quantities of skin friction and Nusselt number are presented in graphical and tabular form. Among the findings of this study is that the Newtonian fluid is a turning point for skin drag force and heat transfer rate. Besides, the ferrohydrodynamic parameter recedes the velocity of shear-thinning fluid the most, although, boosts its (shear-thinning fluid) heat transfer coefficient. [ABSTRACT FROM AUTHOR]

The purpose of the current study is to evaluate the mass and energy transmission of a blood-based Casson Ferrofluid flow across a stretching cylinder. The consequences of the Casson parameter, cylinder curvature, thermal radiation, chemical reaction, and non-Newtonian viscous dissipation are also considered. The nanofluid flow phenomena are mathematically designed in the form of a system of nonlinear PDEs which are degraded and non-dimensionalized to the set of ODEs by using suitable similarity transformations. The homotopy analysis method has been applied to find out a semi-analytical solution for the nonlinear set of ODEs. The significance and physical behavior of flow parameters are graphically characterized versus the velocity, energy, and mass profiles. The numerical outcomes for Sherwood number, drag force and Nusselt number are also presented through Tables. A comparative evaluation has been done for validation purposes to authorize and justify the present results. From the tabular and graphical results, it has been noticed that the velocity profile lowers while the energy profile develops versus the variation of magnetic factor. The impact of curvature factor boosts the velocity and mass transfer rate of the Casson nanofluid while reducing the temperature curve. Furthermore, the consequences of the thermophoresis effect raise the temperature profile of the Casson Ferrofluid flow. [ABSTRACT FROM AUTHOR]

Accurate assessment of rolling resistance is important for wheelchair propulsion analyses. However, the commonly used drag and deceleration tests are reported to underestimate rolling resistance up to 6% due to the (neglected) influence of trunk motion. The first aim of this study was to investigate the accuracy of using trunk and wheelchair kinematics to predict the intra-cyclical load distribution, more particularly front wheel loading, during hand-rim wheelchair propulsion. Secondly, the study compared the accuracy of rolling resistance determined from the predicted load distribution with the accuracy of drag test-based rolling resistance. Twenty-five able-bodied participants performed hand-rim wheelchair propulsion on a large motor-driven treadmill. During the treadmill sessions, front wheel load was assessed with load pins to determine the load distribution between the front and rear wheels. Accordingly, a machine learning model was trained to predict front wheel load from kinematic data. Based on two inertial sensors (attached to the trunk and wheelchair) and the machine learning model, front wheel load was predicted with a mean absolute error (MAE) of 3.8% (or 1.8 kg). Rolling resistance determined from the predicted load distribution (MAE: 0.9%, mean error (ME): 0.1%) was more accurate than drag test-based rolling resistance (MAE: 2.5%, ME: −1.3%). [ABSTRACT FROM AUTHOR]

The results of a numerical study of the flow around a circular rotating cylinder under the subcritical regime of the Reynolds number are presented. A numerical flow simulation was carried out using the Realisable k-ε turbulence model, which effectively visualizes the fallout of vortices. At Reynolds numbers 16,000, 30000, and 50,000 and revolutions 300,500 and 700, the velocity field around the cylinder with the plate and the static pressure distribution field around the cylinder with the plate are obtained. It is determined that with an increase in the rotation frequency of the cylinder with the plate, the vortex formation increases. In the future, there will be an increase in lifting force and drag force due to an increase in flow velocity and, consequently, a decrease in pressure. Due to the rotational motion, there is a change in the pressure field at the ends of the cylinder with the plate. [ABSTRACT FROM AUTHOR]

The current study emphasizes bioconvective viscous fluid flow between two horizontal deformable cylinders. At the cylindrical walls, the Newtonian heat and mass condition with velocity slip is examined. The thermal and solutal transfer is optimized by amalgamating Soret–Dufour effects with variable heat source/sink. The equations that regulate the flow are simplified via appropriate transformations. The bvp4c algorithm is employed to obtain the numerical solution. The ramifications of the emerging parameters are portrayed graphically. Numerical values for drag force coefficient, heat flux, mass flux, and local motile density numbers are enumerated in tabulated form. Axial velocity accelerates on varying the unsteadiness parameter. The thermal field elevates by augmenting the Dufour number and thermal conjugate parameter. The drag force coefficient exhibits a decreasing behavior on enhancing the unsteadiness and velocity slip parameters. An opposite behavior is exhibited by heat and mass flux on amplifying the Soret and Dufour number. Motile density deteriorates on elevating the Lewis number and unsteadiness parameter. A substantial correlation has been noticed by graphically comparing the results of this study with the previous literature. [ABSTRACT FROM AUTHOR]

In the subway system, a high concentration of iron particles can cause significant damage to human health, and magnetic filters that efficiently filter out iron particles have attracted considerable attention recently. Therefore, it is both urgent and important to study the influencing factors of magnetic filters for improving filtration efficiency and reducing resistance. In this paper, to establish a filtration model for magnetic filters, the flow field, magnetic field and particle tracking of magnetic filters are calculated in three steps. After the force analysis of particles, it can be concluded that the particle tracking module needs only to consider drag force, magnetic force and gravity. Based on the filtering model, a two-dimensional magnetic filter was simulated on a computer. and the factors affecting filtration efficiency and resistance were analyzed. It was found that an increase in magnetic field intensity and the diameter of the particle have a positive effect on the filtration efficiency of the magnetic filter, while the increase in airflow velocity and the distance between magnets has a negative effect. The increase in distance between magnets has a negative effect on the resistance of the magnetic filter. In particular, the distance between magnets and the strength of magnets are two of the most influential factors. Finally, two simple formulas concerning the relationship between filtration efficiency, resistance and influencing factors were revealed, by which filtration efficiency and resistance in practical magnetic filter design can be calculated. Copyright © 2023 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

In this study, both experiments and computational fluid dynamics simulations were performed to investigate the transport characteristics of transient high-temperature dust in a tee duct. The experimental results showed that there is a cavity downstream of the main duct. The simulation results showed that the second flow was generated downstream, and the high-temperature dust moved to the top of the main duct owing to thermal expansion and buoyancy. The temperature change in the particles depended on the site, and the temperature of the particles in the center was higher than that of the surrounding particles. The thermal expansion and buoyancy of high-temperature fluids affected the particle motion through the drag force. The deposition of particles was wing-like and was mainly present on both sides of the tee duct, which was five times the diameter of the main duct. This study provides theoretical guidance for the development of industrial ventilation systems. [ABSTRACT FROM AUTHOR]

The integration of chemical looping combustion with fluid catalytic cracking (CLC-FCC) is an innovative concept that serves as a cost-effective method for CO2 capture in refineries. This approach has the potential to reduce refinery CO2 emissions by 25–35%, offering a promising solution. As in the conventional FCC unit, it is common for CLC-FCC regenerators to be exposed to an on-off process while they are being maintained and cleaned. The novelty of this research lies in its specific focus on a less-explored phase (start-up) of CLC-FCC regenerators, the application of advanced CFD modeling, and the comprehensive analysis of operational parameters that influence the system’s performance. To validate the CFD simulations of the different drag models for solid-gas granular, bed density profiles under steady-state conditions, collected from industrial processes, were used. For the flow period based on the start-up process of the drag models, the fluidization gas inlet geometry of the regenerator, flow regime (laminar and turbulent), and superficial gas velocity were comprehensively investigated to reveal their effects on hydrodynamic characteristics. The results show that Gidaspow and Syamlal-O’Brien drag models of the solid-gas multiphase granular flow exhibited a better fit with industrial data. The SyamlalO’Brien and Gidaspow models closely align with industrial data under steadystate conditions, displaying similar bed densities in the dense phase region (230– 310 kg/m³ for Syamlal-O’Brien and 235–300 kg/m³ for Gidaspow). During the initial stage (less than 0.2 seconds), both laminar and turbulent models yield comparable bed density profiles, approximately 510 kg/m³ in the dense phase. However, as the process progresses, the dense phase density decreases to about 250–350 kg/m³ at around 0.5 seconds, with laminar flow models showing a slightly better fit with industrial data. Notably, at 0.5 seconds of fluidization time, inlet geometries having better gas distribution achieve a highly diluted phase with bed densities of 10–20 kg/m³. Reaching a steady state, the bed density decreases from around 400 kg/m³ to 260–300 kg/m³, expanding into a higher section of the regenerator where it aligns well with industrial data. The increase in superficial gas velocity would result in the clarification of the difference and well mixing of the solid-gas multiphase flow. [ABSTRACT FROM AUTHOR]

Compressible flow through a branched duct and the motion of a sphere through a high blockage ratio pipe are two important and engaging topics throughout the years. The results of studies on these topics are of practical relevance to many fields such as the gas pipeline technology, air transport systems in gas turbines technology, and tube transportation, etc. However, studies on the motion of a sphere in a branched duct are scarce. Studies of the motion of a sphere in a near-vacuum tube could contribute to the development of a branched Hyperloop system in the future. In this study, we investigated the effect of the tube curvature radius and angle on the aerodynamic characteristics of a sphere during its motion in a branched tube. We examined, quantified, and compared the variation of the drag, side force, and pressure waves for the cases where a sphere enters a branch considering six curvature radii (from 500 to 3000 m), three angles (10°, 15°, and 20°), three speeds (100, 200, and 300m s-1), and two initial pressures (1/1000 and 1 atm) in simulations. The results indicated that the drag and side force vary only in the intersection region (region where the straight tube and branched tube intersect); before and after the intersection region, they are similar. With an increase in the curvature radius, the rate of drag reduction (FD/max(FD)) decreases, while the changes in the angle do not affect variation of drag and side forces. Furthermore, we compared the motion of a sphere in straight and branched directions and found out that the flow in front and behind the sphere was similar for both directions. [ABSTRACT FROM AUTHOR]

Feedforward neural network (FNN) models with strong learning ability and prediction accuracy are crucial for optimization. This paper investigates the effects of the number of training samples and the hidden layers on the accuracy of the FNN model. Meanwhile, under the premise of a high space-fillingness degree, a sample expansion strategy based on the max--min distance criterion is proposed, which ensures that the expanded sample set completely contains the pre-expanded. The strategy can eliminate the interference of sample differences. Furthermore, the multi-objective optimization on the train nose shape is accomplished by minimizing the aerodynamic lift force of the tail car (LT), as well as the aerodynamic drag force of the head (DH) and tail car (DT) using the FNN model. The results indicate that the number of training samples has a greater impact on the prediction error of the FNN model than the number of hidden layers does. Prediction errors decrease as the number of training samples increases and then stabilise, the most accurate one is chosen for nose shape optimization. The DH, DT, and LT all have prediction errors of less than 2%. Compared with the original high-speed train, the DH, DT, and LT of the optimal model are reduced by 5.24%, 3.74%, and 2.61%, respectively. Meanwhile, the correlation analysis reveals that the height of the cab window and the horizontal profile have a significant impact on the aerodynamic characteristics of the high-speed train. [ABSTRACT FROM AUTHOR]

In this paper, we developed a mathematical model to simulate virus transport through a viscous background flow driven by the natural pumping mechanism. Two types of respiratory pathogens viruses (SARS-Cov-2 and Influenza-A) are considered in this model. The Eulerian–Lagrangian approach is adopted to examine the virus spread in axial and transverse directions. The Basset–Boussinesq–Oseen equation is considered to study the effects of gravity, virtual mass, Basset force, and drag forces on the viruses transport velocity. The results indicate that forces acting on the spherical and non-spherical particles during the motion play a significant role in the transmission process of the viruses. It is observed that high viscosity is responsible for slowing the virus transport dynamics. Small sizes of viruses are found to be highly dangerous and propagate rapidly through the blood vessels. Furthermore, the present mathematical model can help to better understand the viruses spread dynamics in a blood flow. [ABSTRACT FROM AUTHOR]

The key function of lubricants is to reduce the friction, wear, and heat between the parts that are in contact with each other. The main applications of the lubricants are to control temperature, and reduction in wear and corrosion of the machinery. Keeping in mind the importance of lubrication and its applications in varied machines. The goal of this research is to inspect the heat transmission impact in the magnetohydrodynamic flow of Jeffrey liquid near a stagnation point through a lubricated surface. Lubrication is accomplished by a shear-thinning liquid. The velocity, continuity, and shear stress, amalgamated with power-law fluids, are used to develop interfacial conditions. The exclusivity of the anticipated model is the inclusion of variable thermal conductivity and diffusion coefficients in the existence of homogeneous-heterogeneous reactions. Using the Keller–Box finite-difference approximation approach, the numerical results are accomplished. The outcomes are portrayed and tabulated in the form of diagrams and tables, respectively. It is witnessed that a greater magnetic field affects the fluid flow velocity and the drag force coefficient. Moreover, it is also inferred that the heat transfer rate dwindled for the greater thermal conductivity parameter. Authentication of the presented model is also part of this investigation. [ABSTRACT FROM AUTHOR]

Nanofluids with immersed metallic nanoparticles possess a higher thermal conductivity. The extent of this enhancement is largely dependent on the amount of the volume fraction, composition, nanoparticles' shape, and size. The current study emphasizes nanofluid (gold-ethylene glycol) flow with different shapes past a horizontal infinite permeable conduit. The porous walls exhibit the fluid to move in or out of the channel as the walls expand or contract. The flow problem is modeled in a Cartesian coordinate system by employing the Tiwari-Das nanofluid model. Heat transfer is enhanced with the inclusion of Cattaneo–Christov combined with heat generation/absorption effect and temperature-dependent thermal conductivity. The Hamilton–Crosser model is adopted here for the cylindrical and platelet shapes nanoparticles. By invoking appropriate transformation, the equations are transmuted into ordinary differential equations and are solved numerically by employing the bvp4c approach. The influence of the key parameters is illustrated graphically. A protuberant decline is observed in the cylindrical shape nanoparticles in the thermal field on augmenting the thermal relaxation parameter. The drag force coefficient elevates on incrementing the volume fraction of nanoparticles. A significant correlation is noticed in the findings of the comparison with the existing literature. [ABSTRACT FROM AUTHOR]

This work presents the first results using Smoothed Particle Hydrodynamics (SPH), a mesh-free technique, to simulate underwater vehicle motion with the goal of achieving sufficient physical realism and computation time performance capabilities. The objective is not to get very accurate values for the hydrodynamic parameters, but to show that SPH can simulate hydrodynamic parameters with the same order of magnitude as the reference, in order to allow a realistic control of robots in water. First, spherical objects are simulated to check buoyancy realism, speed limit existence, and hydrodynamic parameters in comparison with reference values. Then, horizontal and vertical movements of a capsule-shape object and a real torpedo-shape underwater robot are compared. The results show that buoyancy is respected, and that spherical objects reach a speed limit in accordance with the laws of physics. In addition, added-mass is simulated with 20 % variation on average with respect to the reference and varies homothetically with respect to the object's size. In contrast, drag forces cannot not be simulated with the same level of realism without reducing the particle size, which makes the simulation last longer. SPH for underwater robotics simulation appears to be promising, and ways of further improvements are being considered. [ABSTRACT FROM AUTHOR]

An analytical and experimental study of flow velocities within submerged canopies of rigid cylinders under oscillatory flows is presented, providing insights into the momentum transfer mechanisms between the different flow harmonics. The experimental dataset covers an unprecedented wide range of flow amplitudes with in-canopy velocity reductions ranging between 0.2 and 0.8 of the free stream velocity (from inertia- to drag-dominated in-canopy flow). Results from the analytical model with nonlinear drag compare favourably to the experimental data. Having application of theories for free surface waves over canopies in mind, the effects of linearization of the drag are analysed by comparing sinusoidal and nonlinear model predictions. Finally, a unified prediction formula for in-canopy velocities for sinusoidal, velocity-skewed, and velocity-asymmetric free stream velocities is presented. The formula depends on two non-dimensional parameters related to inertia and drag forces, and the unified formula allows for easy assessment of the maximum in-canopy velocity. [ABSTRACT FROM AUTHOR]

Moonpools are holes in the middle of a ship's hull and through its deck. In this study, the flow mechanisms in moonpools in calm water were investigated. Star-CCM+ software was used to calculate the flow within a two-dimensional (2D) moonpool under uniform flow conditions. A 2D moonpool numerical calculation model was constructed, and the convergence analysis results and experimental data were used to verify the accuracy of the calculated results. Flow field and free surface fluctuations are the main factors that cause the drag force of the moonpool. The drag force increases with the flow velocity, and the drag coefficient presents different trends at different stages. With an increase in the Froude number, Fr, the 2D moonpool enters the frequency lock-in state of the piston and sloshing natural frequency. Additionally, increasing the moonpool length results in a nonlinear change in the flow state. [ABSTRACT FROM AUTHOR]

Swimmers generate vortices around their bodies during underwater undulatory swimming (UUS). Alteration of UUS movement would induce changes in vortex structure and fluid force. This study investigated whether a skilled swimmer’s movement generated an effective vortex and fluid force for increasing the UUS velocity. A three-dimensional digital model and kinematic data yielded during UUS with maximum effort were collected for one skilled and one unskilled swimmer. The skilled swimmer’s UUS kinematics were input into the skilled swimmer’s model (SK-SM) and unskilled swimmer’s model (SK-USM), followed by the kinematics of the unskilled swimmer (USK-USM and USK-SM, respectively). The vortex area, circulation, and peak drag force were determined using computational fluid dynamics. A larger vortex with greater circulation at the ventral side of the trunk and a greater circulation vortex behind the swimmer were observed in SK-USM compared to USK-USM. USK-SM generated a smaller vortex on the ventral side of the trunk and behind the swimmer, with a weaker circulation behind the swimmer compared to SK-SM. The peak drag force was larger for SK-USM than for USK-USM. Our results indicate that an effective vortex for propulsion was generated when a skilled swimmer’s UUS kinematics was input in the other swimmer’s model. [ABSTRACT FROM AUTHOR]

A numerical analysis is performed to scrutinize the heat transport of the Sutterby hybrid nanofluid flow between two concentric cylinders. This work incorporates ethylene glycol as a base liquid immersed with Al2O3 and TiO2 nanomaterials. A uniform magnetic field is employed in the existence of radiative heat, Ohmic heating, and in homogeneous heat production or absorption to investigate base fluid and hybrid nanofluids' motion and thermal transfer properties. The flow model is constructed and solved mathematically utilizing the Keller–Box method and MATLAB software. Comparable outcomes for base liquid and cross-nanoliquid are discovered and explained. The subject of the research work is the use of solar energy with parabolic trough solar collectors. It is discovered that the thermal transmission rate of hybrid nanofluid is more remarkable than base liquid. The magnetic field's drag force can control the flow and heat regions. [ABSTRACT FROM AUTHOR]

A large proportion of flow resistance can be due to vegetation in open-channel flows. Classic methods are unable to estimate flow resistance in the presence of vegetation. In this study, drag coefficient was estimated as a parameter to represent the flow resistance in emergent and submerged vegetation patches with different densities. Emergent vegetation was simulated by wooden cylinders 8 mm in diameter and 0.35 m high. Four emergent patches with different densities, arrangements, tandem, random, and circular, were examined. Also, submerged vegetation was simulated by nails 4 mm in diameter and 4.5 cm in height. The phenomenon of dip occurred throughout the dense patches because of secondary flow and the drag force generated by vegetation. Four methods were selected to estimate the drag coefficient and the balance approach-blockage factor method was used as the main method to estimate the patch drag coefficient. Results showed that velocity profiles were S-shaped and the drag coefficient of random vegetated patches was greater than the coefficient of tandem patches. The drag coefficient revealed a direct relation with vegetation density. In all patches, the initial rows had the highest contribution to flow resistance, so the drag coefficient decreased through vegetation patches. [ABSTRACT FROM AUTHOR]

Advanced ball bearing simulations require the use of accurate tribological models, starting with the calculation of the ball-race contact load and pressure in potentially truncated contacts. Ball—cage and cage—guiding ring contact stiffness models are suggested using the Hertzian contact stiffness and/or a structural stiffness. The central ball-race film thickness, a hydrodynamic rolling force, and normal load increase are calculated using relationships respecting miscellaneous lubrication regimes, including iso-viscous-rigid or piezo-viscous-elastic. A drag force acting at the ball center is included, and its magnitude discussed for claiming that the contribution from drag to the final rolling resistance is smaller than the one from hydrodynamic rolling acting at the ball-race contact. The central film thickness and sliding speed are used for defining shear rate, shear stress, and, hence, final sliding force, using a nonlinear visco-elastic-plastic lubricant rheological model including viscosity, elastic lubricant shear modulus, and limiting shear stress, which are all functions of the pressure and temperature. Elastic effects are approximated using a simple nonlinear visco-plastic model with apparent viscosity. The temperature is defined as the sum of the operating temperature and several other sources of temperature increase. It is observed that when adopting Roelands viscosity model and a simple nonlinear visco-plastic model, the final lubricant traction coefficient and its gradient with respect to sliding speed decrease as the rolling speed increases, mostly reducing the need for a lubricant elastic shear modulus. Appropriate experimental results are highlighted to support these analytical models. [ABSTRACT FROM AUTHOR]

In this work, a numerical analysis of the mechanics of the interaction of the red blood cell with the vessel wall was carried out. The deformation process is described using an adhesive dissipative elastic model. The influence of the electrostatic double layer and drag force on erythrocyte is investigated. The discrete element method is used to model erythrocyte dynamics. The focus is on the analysis of the effect of different acting forces on the erythrocyte. The results reflect force, displacement, time dependencies. The results indicate the process of erythrocyte deformation before contact, at certain distance from the interacting vessel surface. [ABSTRACT FROM AUTHOR]

Sediment transport in the swash zone directly affects beach changes such as shoreline recession; thus, detailed understandings of sediment transport mechanisms are necessary to accurately estimate the short-time scales sediment transport rate. However, these detailed mechanisms under runup waves have not been elucidated because of the complex solid-gas-liquid multiphase turbulence flow. In this study, we attempt to numerically investigate the sediment grain-scale mechanism to overcome the shortcomings of experimental measurements and the free surface treatment in many numerical simulations. The gravel transport process on a sloped beach under regular waves was simulated using a 2D coupled model of the discrete element method (DEM) and a modified moving particle semi-implicit (MPS) method; a sub-model was built into the DEM-MPS model to improve fluid volume conservation. After validating the simulated performance by comparing it to a previous experiment, the gravel motions were investigated for turbulence and inner beach structure. The Shields number, estimated using the drag force distribution, revealed that significant turbulence contributed to onshore gravel transport near the rundown limit. The inter-gravel contact structure inside the beach explained the decrease in offshore sediment transport during backwash as increased resistance to gravel motions resulting from beach compaction. [ABSTRACT FROM AUTHOR]

Improving marine vehicles performance by reducing energy consumption, decreasing environmental pollution, increasing speed and range has always been the goal of engineers for optimal designs. Nowadays, inspiration from nature is one of the scientists' approaches to solve many engineering problems. The researchers, by mimicking the skin of some marine species, such as fast swimming sharks, dolphins and sailfishes have been succeeded to design and fabricate drag reducing microstructured surfaces. In this research, after describing various types of fish scales, a Ctenoid-shape microstructure is designed by inspiration from bony fish scales. Then, the designed microstructures with various dimensions are implemented on an underwater hydrodynamic model to evaluate its ability to reduce drag force. Models numerically analyzed at different Reynolds numbers for turbulent flow regime utilizing the k-ω SST turbulence model. Furthermore, the effects of Ctenoid-shape microstructure on the different drag components including form drag and friction drag have been examined separately. The results indicated that the Ctenoid-shape microstructured surfaces applied to the underwater hydrodynamic model in the optimum condition have reduce the total drag force on average 20% in turbulent flow range. [ABSTRACT FROM AUTHOR]

Along the banks of rivers, trees and bushes are often planted in a single line. In the case of trees, the trunks are simulated in hydraulic laboratories by a set of cylinders, and the drag coefficient can be estimated with the use of various different methodologies, including by direct measurement, using the momentum equation, equating turbulence intensity and drag force, numerical modeling, and genetic programming. However, for the sake of simplicity, many equations have been proposed in the scientific literature that allows its immediate estimation. Some of these equations are used in this work to verify their ability to reproduce experimental data obtained for in-line cylinders by Mulahasan and Stoesser ([2017]. Flow resistance of in-line vegetation in open channel flow. International Journal of River Basin Management, 15(3), 329–334. https://doi.org/10.1080/15715124.2017.1307847), who obtained the drag force by applying the momentum equation. Several statistical descriptors have been used for this purpose. We found that the equations derived from staggered and random arrangements generally overestimate by a large amount the CD values; instead, a few relationships and in particular one derived from a squared arrangement provide much better results. [ABSTRACT FROM AUTHOR]

This study focuses on the comprehensive analysis of the thermal characterization of an electrically conducting nanofluid flow containing TiO2 nanoparticles dissolved in two different common liquids (H2O and C2H6O2) and contained within a continuously extending disk. The heat and concentration formulation are modified by incorporating the standard interpretations of the Joule heating, energy source, dissipation, and modified activation energy with binary chemical reactions. The Darcy–Forchheimer addition is used to highlight the significance of porous media. The Brownian dispersion's effects are clearly discernible in the current investigation. Furthermore, as a novelty, special thermophysical models of viscosity and thermal conductivity are included. The obtained differential formulations are tackled through the analytical procedure HAM. The veracity of the finding is verified through a numerical scheme (ND-solve technique). Using several graphs and charts, the perception trends of model factors are evaluated. The influence of C f z , N u z , and S h z are estimated based on flow characteristics. The F ′ (ζ) curve pattern for both nanofluids is declined by the increasing magnitude of M , ϕ , β p * , and F r * , while thermal profile. The drag force and heat transmission rate are shown to optimize with M as well as ϕ in the pictorial simulations produced from the existing model. The Φ (ζ) can also be strengthened by the presence of a high degree N b. The outcomes are validated by previous studies and a good degree of consistency is revealed. [ABSTRACT FROM AUTHOR]

The silver and gold nanoparticles display noteworthy results in antimicrobial and anticancer therapies. Silver is a considerable anti-inflammation, and gold nanoparticles effectively use to convert the photons to heat to destroy cancer cells. By keeping this in view, we investigated the radiative heat allocation in blood-based Ag-Au hybrid nanofluid flow. We assumed a blood vessel with cosine stenosis in the existence of an aligned magnetic field and variable heat source/sink. The flow model was developed to investigate the underlying physics and solved numerically after applying appropriate transformations. The computational outcomes for the flow and energy fields were explored through graphical and numerical illustrations. Also, the consequences of local Nusselt number and wall friction were discussed. The outcomes are validated and found to be in noble agreement. It is noticed that the inclined magnetic angle can control the drag force and heat transmission. Also, the Ag-Au combination effectively enhances the rate of heat transfer. This may help the effective conversion of photons to heat energy used in cancer therapies. [ABSTRACT FROM AUTHOR]

Ships in service feature surfaces that exhibit biofouling, which alters the hydrodynamics of the vessels, thus affecting their normal displacement and significantly increasing their fuel consumption. The application of three types of ceramic coatings as ecological, effective and durable alternatives to commercial silicone-based marine coatings is investigated in this study. Three different ceramic glazes and two control commercial paints are analysed in an actual environment during 20 months of exposure to simulate the navigation conditions such that growth and roughness data can be obtained and then applied to computational fluid dynamics (CFD) software using an open-source Reynolds-averaged Navier–Stokes solver. The CFD results are validated under smooth hull conditions with a full-scale Kriso Container Ship (KCS) model and with different levels of hull roughness. The developed approach shows that the drag in hulls coated with conventional paint is 19% greater than that in hulls with ceramic coating. [ABSTRACT FROM AUTHOR]

In this article, a dynamic electrostatic separation experimental device was set up. The experimental results show that with increasing packing height, inlet velocity and voltage, the saturated adsorption weight slowly increases. When the inlet velocity is greater than 2.379 × 10−4 m/s, the drag force plays the dominant role and the saturated adsorption weight decreases. The packing height and voltage are positive parameters for the separation efficiency, while the inlet velocity is a negative parameter. Through the nonlinear fitting of experimental data, the saturated adsorption weight, and dynamic electrostatic separation efficiency model of the device were obtained. [ABSTRACT FROM AUTHOR]

The settlement characteristics of magnetite particles are one of the key factors affecting the separation performance of column magnetic separator. This paper reports on the settlement characteristics of different magnetite particles under the action of complex force field measured by using a particle settlement device with an applied magnetic field. The results show that under the combined effect of fluid drag force and magnetic field, the differences in magnetite particle density and particle size are reduced, the differences in magnetic properties are amplified, and particles with different magnetic properties are separated. Based on these results, a three-product magnetic-separation column with mutually independent magnetic and fluid field structures for different magnetic particles was developed. Using this separator, the TFe grade and recovery of the concentrate were 67.93% and 92.9%, respectively. The results show that the equipment is effective in separating the liberated magnetite and other interlocking particles, thereby improving the sorting efficiency. This provides a theoretical basis for the development of column magnetic separation equipment and the improvement of magnetic separation accuracy. [ABSTRACT FROM AUTHOR]

With China already committed to peak carbon dioxide emissions before 2030 and aiming at achieving carbon neutrality before 2060, coal separation has recently become a hot research topic, in particular, gas–solid fluidized separation technology has attracted significant research attention. Coal particles with size of +10 mm can be separated efficiently via currently used technologies; nonetheless, specific scientific problems of fine coal separation still need to be systematically explored. In this study, combined with the properties of coal particles, a density model of fine coal in fluidized bed separation process was proposed. The separation effect was found to be better with the increase of feeding coal particle size, in particular, the coal particles with size larger than 5 mm underwent effective separation. The results reveal that the drag force of the fine coal separation process is an important factor restricting the separation efficiency. Fluidization theories, such as pressure drop, gas–solid two-phase model, and particle sedimentation theory could explain that with the decrease in the feeding coal particle size from 10 mm, the probable error E value increases from 0.105 to 0.355 g/cm3, the misplaced material content M increases from 5.48% to 16.13%, and the lower limit of the separation is controlled at 5 mm. This helps to enhance the processing capacity and increase the separation granularity range of the fluidized bed. [ABSTRACT FROM AUTHOR]

This study addresses analytical modeling and the assessment of a vertical axis turbine (VAT) with blade pitch adjustment by an eccentric guide, which is focused on applications with low tip speed ratio (TSR ≤1.5), hence focused mainly on the drag principle. This study aims at investigating a new proposal of vertical axis turbines with movable blades that promote an increment of overall efficiency by reducing drag forces during the contrary motion to the flow direction. Based on this approach, drag forces are significantly reduced and a positive torque is generated by lift forces during the contrary motion to the incoming flow, which provides the performance improvement of VAT. This novel concept is solved analytically for blades with 17 distinct airfoil profiles, and a parametric analysis is performed by varying guide radius, blade length, pitch offset, and tip speed ratio. According to the results performed in this study for a single-blade system, the proposed concept presents a power coefficient of 2.87% regarding the airfoil profile LN118 with a tip speed ratio of 1.0. Similarly, the airfoil profile s1210 has also been a relatively high-power coefficient of 2.09%, but with a tip speed ratio of 0.225. Symmetrical airfoil profiles provided lower power coefficients in comparison with nonsymmetrical, presenting maximum power coefficient for tip speed ratio lower than 0.3. It is worth highlighting that the novel concept of blade pitch adjustment is feasible by a passive system based on a cam-follower mechanism. [ABSTRACT FROM AUTHOR]

This paper has focused on the study of flow characteristics of a steady conductive fluid through a circular pipe in the presence of an applied transverse uniform magnetic field. A numerical simulation of the fluid flow was performed using a multiphysics computational tool. The radial velocity distribution due to the effect of the tangential component of induced magnetic flux density and electric fields at various axial positions is examined in metallic and non-metallic surfaces of the circular pipe. This simulation study helps to analyse the effect of drag force on the variation in axial velocity close to the metallic and non-metallic walls. The induced electric potential is directed along the normal to the Laplacian tangential surface of the pipe. In addition to that, sigmoidalshaped field profiles are observed when the fluid flow crosses from the upstream to downstream of the magnet edge and vice versa along the axial length of the circular pipe. Simultaneously, it is observed that the average velocity of the fluid flow decreases for a laminar and increases for turbulent Reynolds number. Streamline plots pertinent flow variable such as flow velocity are presented for non-conducting and conducting walls. [ABSTRACT FROM AUTHOR]

The transport of micron-sized sand particles in the ribbed cooling duct of the turbine blade determines its deposition characteristics. This paper establishes a prediction function of the coefficient of recovery for 1–20 µm sand particles impact to DD3 Nickel-based single crystal superalloy, varying with impact velocity, impact angle, particle size, and temperature, based on the temperature-dependent elastic-plastic particle collision model. The fitted COR function is evaluated to be accurate and efficient. Then, studies the transport and accumulation of micron-sized sand particles in the ribbed cooling duct with gas-particle two phases flow method considering particle-wall collision, drag forces, pressure gradient forces, etc., of which the particle-wall collision predicts by the established function. Results quantify the significant effect of rib structure on flow features and transport of sand particles transport in the cooling duct, particularly for particles below 10 µm. The transport of fine dust is dominated by the turbulent flow dynamics and particle-wall collision, leading to severe particle accumulation at the rib-wall junction. Particles accumulation nearby the ribs is sensitive with the sizes, and the number of the accumulated particles increases slightly with the increase of temperature from 1,073 K to 1,273 K. [ABSTRACT FROM AUTHOR]

In the fourth generation of industrialization, computer analyses have been captured a lot of attentions in many different areas. For achieving accurate and reliable results, understanding experimental phenomena and comparing them to the computer output should be considered a reliable technique. The main purpose of this study is the comparison of experimental result of aerodynamic/hydrodynamic behavior of coated fabric by hydrophobic finishing with computational fluid design (CFD) to optimize the drag force of swimsuit fabric coated by silica nanoparticles. In this study, swimsuit fabric samples were treated by hydrophobic finishing and then wind tunnel setup used for understanding aerodynamic/hydrodynamic behavior of samples. CFD was also used for simulation of swimsuit behavior with the same characteristics of experimental samples. Both experimental and CFD analyses were then compared, and the results were analyzed to provide the optimum parameters of drag force for the swimsuit fabrics. Results showed that using CFD, optimum swimsuit designing parameters can be achieved more accurately. After primary tests for improving CFD output, it was concluded that variables such as number of meshes, turbulence model, and number of iterations play an important role in simulation output. The results revealed that number of 50 meshes, K-epsilon model for turbulence and number of iterations 1,000,000 are the best condition to study the drag force of simulated swimsuit fabrics. The comparison of experimental drag force and simulated drag force reveals that choosing right variants from experimental plays an important role in CFD output. [ABSTRACT FROM AUTHOR]

Mussel farms are common structure to culture shellfish in the open sea. A numerical model is developed to analyze the interaction between mussel farm and waves, in which the mussel droppers are simulated as porous media. The surface elevation around porous breakwater and the force on mussel dropper from physical model tests are applied to validate our numerical model for simulating the interaction between waves and porous media. Furthermore, the effect of spacing between two adjacent mussel droppers on the force acting on mussel droppers is discussed, and the interaction between mussel farm and oblique waves is also analyzed. The results indicate that the drag force on the downstream mussel droppers is decreased significantly with the decrease of spacing, and it is sensitive to the spacing when the spacing is smaller than three times the diameter of mussel dropper. [ABSTRACT FROM AUTHOR]

The oilwell drilling fluid flows cause viscous and hydrodynamic forces on drill strings. This effect is ignored or treated as a constant in most drill string models. The present study introduces mathematical models for lateral vibration damping and axial drag forces that are employable in lumped segment drill string models. First, the variables to which drilling fluid-generated forces are most sensitive were identified and the Response Surface Method was applied to design the experiment matrix. The lateral vibration-damping experiments, which were validated using a scaled-down physical model, and the axial drag experiments were done using Fluid-Structure Interaction simulations. The results were statistically analysed to acquire the models and were implemented in a 3D lumped segment bond graph developed using the Newton-Euler formulation and body-fixed coordinates. The results indicate a considerable effect of the extended treatment of damping and axial drag on bending moment fluctuation, wellbore interactions, and weight on bit. [ABSTRACT FROM AUTHOR]

Targeted magnetic drug delivery (TMDD) is a promising approach relevant to multimodal cancer therapy. A majority of the TMDD models represent a mixture of blood and nanoparticles as a one-phase solution. However, in many cases it is an oversimplistic assumption. The existing two-phase models are usually one-way coupled, i.e. the blood flow has an impact on the MN flow. However, the inverse impact of the MNs on the the blood is not included. To eliminate these drawbacks the model is governed by two–way coupled momentum and temperature equations for the blood flow and the MN. The numerical procedure invokes the stream function–vorticity formulation and an efficient numerical procedure. The model, validated by experimental results, has been applied to analyze the formation of vortices generated by a combination of the magnetic force (MF) and the drag force (DF). The model also simulates the zones of TMDD and the corresponding changes in the vorticity. Finally, the model includes the impact of the size and concentration of the MNs on the temperature of the blood. These important scenarios cannot be analyzed by the earlier models. [ABSTRACT FROM AUTHOR]

A magnetic-levitation system using a rotating permanent magnet has been developed. Pole pitch of the magnetic wheels and thickness of the metal plates required for levitation were investigated by experiments and computational calculation. To determine the optimum conditions, the levitation force, generated using motors with different torque and rotation speeds, was measured. These measurements clarified differences in the generated levitation force due to the different rotational speed and torque. Parameters, such as skin depth, magnetic density, eddy-current distribution density, the ratio of drag force to levitation force, and levitation force per driving power were numerically calculated from the magnetic field created by the rotating permanent magnet and effective frequency. Magnetic wheels should be designed to be large and the pole pitch of magnets was to be wide, and the levitation force per driving power will be improved in proportion to the root function of the pole pitch between magnets. [ABSTRACT FROM AUTHOR]

The study of flow around a square caisson considering the combined effects of free surface, free end and bottom boundary is limited. Experiments were performed in this study to investigate the characteristics of current forces on a square caisson model considering the combined effects of free surface, free end and bottom boundary. Results show that the drag coefficient and the root mean square coefficient of transverse force generally increase with aspect ratio (AR), and significantly increase at the instant when the free end disappears. The bottom boundary decreases the values of root mean square coefficients of drag force and vertical force. The drag coefficient decreases with incident angle ( α) when 0 ∘ ≤ α ≤ 15 ∘ , but increases with α when 15 ∘ ≤ α ≤ 45 ∘ . The trim and squat phenomenon caused by shallow water effect when the caisson is nearly touching the riverbed (seabed) during the sinking process should receive extra attention in practice. [ABSTRACT FROM AUTHOR]

In this study, the effect of the freight train formation on the train aerodynamic performance was studied. Six cases involving a locomotive (LM) and three different freight vehicles – a boxcar (BC), a tanker (TK), and a double-container freight wagon (DW), were compared and analyzed. The results showed that the aerodynamic drag was significantly affected by the freight train formation type, and the total drag force in Case 2 (LM + BC + DW + TK) was the smallest. Furthermore, the flow field around the train was analyzed to reveal the influence mechanism of the different types of freight train formations on the aerodynamic drag. The car position and the adjacent cars had significant effects on the aerodynamic characteristics of the train. The DW had a greater effect on the pressure and velocity distributions around the train. In addition, the variations of the vortices in the near wake of the same tail car were inconsistent, although there were similar characteristics for the same tail car. [ABSTRACT FROM AUTHOR]

Bubble formation and detachment in liquid cross-flow widely existed in industrial systems. In this work, an integrated theoretical model based on a global force balance on the bubble detaching from a wall orifice in high liquid cross-flow is established to give a comprehensive description of bubble detaching process. The bubble detachment diameter are predicted by the model, and the effect of variation forces acing on bubble surface caused by liquid velocity, air flow rate and orifice diameter on bubble detachment is analyzed. Predictions of the theoretical model compare well with the previous experiment. In the horizontal direction, the liquid inertia force is the main detaching force, and the liquid drag force plays an important role in the early stage of bubble detachment. Because of the different liquid flow rate, the resultant force change has great influence on bubble detachment. However, due to the difference of gas flow rate and orifice diameter, the change of resultant force has little effect on bubble detachment. The relationship between gas–liquid momentum ratio, orifice diameter and bubble detachment diameter is fitted. When the ratio is less than 0.2, the liquid inertia force and drag force caused by liquid velocity has a great influence on bubble detachment diameter. When the ratio is greater than 0.2, the effect of liquid velocity is gradually weakened, and the bubble detachment becomes difficult due to the increase of air flow. [ABSTRACT FROM AUTHOR]