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The use of high-performance single screws, such as barrier and wave-dispersion screws, is steadily increasing in polymer processing operations. In these screw types, regions with deep channels are found, where the polymer melt flow is markedly affected by channel curvature. Aiming for an accurate prediction of the flow rate and viscous dissipation rate, the governing equations for three-dimensional viscous fluid flow were developed in a helical reference frame. In contrast to previous modeling approaches, two helical coordinates in down-and cross-channel direction were introduced, which allows a more direct comparison with the flat plate theory. To reduce the complexity of the problem, focus was placed on an isothermal and fully developed flow of a power law fluid in fully confined channels of unit length. After conversion into a dimensionless form, the equations reveal five influencing parameters on the flow: (i) the channel depth ratio, (ii) the screw pitch ratio, (iii) the channel aspect ratio, (iv) the power law index, and (v) the dimensionless down-channel pressure gradient. The effect of channel curvature is described by the channel depth ratio and appears threefold: (i) net forces and deformations due to the locally changing orientation of the channel, (ii) additional flow coupling due to the twisted channel cross-section, and (iii) variable curvature radius and down-channel arc length across the channel depth. The resulting mathematical framework can be implemented into various numerical solution techniques to investigate and optimize the melt conveying behavior of single screw pumps. [ABSTRACT FROM AUTHOR]

This paper presents a study of the design of a wing-mounted with a morphing winglet, along with its aerodynamic and structural analysis. The concept of span-wise morphing of winglets is proposed as it is an effective technology for enhancing aerodynamic efficiency and has the potential to replace conventional control surfaces. Further, the main advantages of variable span morphing winglets are the drag reduction that leads to an increase in range and endurance of the flight. The design includes a honeycomb core placed in between the skin of the winglet where span-wise morphing occurs to increase the structural integrity. Two actuators are used which are fixed at the rib of the winglet to carry out the span-wise morphing of the winglet. For aerodynamic analysis, ANSYS Fluent solver is used to investigate a flow field in a three-dimensional wing structure and to obtain lift/drag variations. It was observed that a 25% extension in span leads to a 4% increase in overall L/D. This shows that morphing in winglets can be a profound way to increase the aerodynamic efficiency of aerial vehicles [ABSTRACT FROM AUTHOR]

Electronic circuit cooling has become a critical consideration in the development of electronics. Overheating might result in hardware malfunctions or damage. Air-cooling is an efficient invention to the Printed Circuit Board (PCB) cooling, and the real motherboard ASUS X399-A is inspected by simulation experimentally and numerically. Finite volume method CFD procedure is employed to pattern the forced convection laminar air-cooling flow in a three-dimensional motherboard. Experiments are performed on the motherboard to simulate the PCB in both horizontal and vertical orientations with a processor full load heat power of 130 W. The results proved that there is an enhancement in heat transfer in the horizontal position from the vertical position in the same working conditions. [ABSTRACT FROM AUTHOR]

In this work studied a fluid's pressure loss in a turbulent incompressible flow through a two-variable angle 90°and 45° junctions were predicted and compared with analytical results. In the numerical simulations, for the flow rate ratios, one turbulence model was utilized between the main pipe and the branch pipe: the k-model. a method based on finite volumes was used to disprove the continuity and momentum equations, and the coupled system was accustomed connect the fields of pressure and velocity from inside of the domain. ANSYS FLUENT17 was used to solve a three-dimensional steady-state flow problem. at various in the range of Reynolds numbers (2500-30300), the findings show that the loss coefficient is unaffected by the number of Re. the impact it was calculated the pressure drop and velocity profile are affected by the ratio of flow rate q (the ratio of flow rates in branch and exit pipes). in the 90° junction, the pressure loss coefficient started with 0.85 in leg 1-2 and then decreased until it reached 0.2, but in leg 1-3, the pressure loss coefficient started with 0.6 and gradually increased until it reached 2.3. On the other hand, in the 45° junction, the pressure loss coefficient leg 1-2 started with 0.87 and then decreased until it reached 0.43, and in leg 1-3, it started with 2.4 and then decreased to 1.9, due to recirculation and a considerable streamline curvature, the outcomes disclose that results reveal that when the pressure and total energy losses rise, the float charge ratio will increase. [ABSTRACT FROM AUTHOR]

This paper aims to present the impacts of magnetic force applied with an angle of inclination and velocity slip on three dimensional stream of micropolar liquid over a nonlinear elongated sheet with convective boundary conditions. The influences of thermal radiation and temperature dependent heat source/sink are also reckoned. With the aid of similarity variables, the coupled partial differential equations of momentum and thermal energy are transformed into a set of ordinary differential equations and their solutions are established by adopting the Runge – Kutta method jointly with shooting technique. The insight of the flow nature is discussed through graphs and tables varying the physical parameters emerged in the analysis. The outcomes of this study are compared with the results already published as a limiting case and are found to be in fairly good agreement. [ABSTRACT FROM AUTHOR]

Solving the reduced Navier-Stokes equation for the calculation of the flow of non-Newtonian polymer melts in single screw extruders numerical methods are needed. In this study, a numerical model, based on the finite difference method, for the description of the one- and two-dimensional fully developed conveying characteristics of power law fluids in the melt channel will be introduced. Furthermore, the two-dimensional model will be enhanced by considering the real cross-section of the screw channel and introducing adaption factors which approximate the fully developed three-dimensional flow behavior in the screw channel. Finally, a comprehensive comparison with CFD-Simulation results will be done. Therefore, a parametric study with three independent parameters, pitch to diameter ratio, width to height ratio and power law exponent, will be done and both, viscosity- and velocity-profiles as well as the calculated πm / πP − characteristics will be compared to CFD-Simulation results. [ABSTRACT FROM AUTHOR]

Pumping is a key processing step in all single-screw extrusion operations. Forcing the polymer resin through the die at the discharge end of the processing machine requires the extruder screw to generate pressure, which may develop at various levels in all functional zones, depending on the design of the screw-barrel configuration. The total pumping capability of the single-screw extruder is therefore determined by the geometry of the entire screw. Since the geometry of each screw section varies, the validity of existing melt-conveying models must be critically reexamined when predicting the pumping capability of a single-screw extruder. Numerous theories for the prediction of flow rate and pressure build-up in extruders have been published: While most are based on the flat-plate approximation, only a few include the effect of channel curvature. Assuming flow of power-law fluids, this work compares screw characteristic curves of flattened and curved screw channels for two- and three-dimensional flows, in which the influence of the screw flights is either ignored or considered, respectively. By solving the governing equations for these flow situations, we demonstrate the distinct differences between these modeling approaches. We further analyze the usefulness of each method in relation to the underlying screw geometries. [ABSTRACT FROM AUTHOR]

CFO analysis is an essential tool in the design and development of a conical rocket nozzle. Grid generation plays a crucial and time-consuming role in any cod analysis. In this work, cod analysis of conical rocket nozzle has been carried out using fluent software. The three-dimensional hybrid grid has been generated using gambit software. The effects of the injection of the secondary jet on the flow field of secondary gas injection for thrust vector control (sit) were numerically investigated. Three-dimensionalReynolds-average navies-stokes equation with an algebraic turbulence model solved the complex three-dimensional nozzle flows perturbed by the secondary gas jet. Parameters such as mach number and nondimensionalised radial distance has been estimated and compared with experimental measurements. Flow dynamics and contours with different parameters have been analysed and published. Of the various ways in which the deflection can be performed, tic has been successfully applied primarily to reliable engines employing secondary injection of matter, including secondary gas injection for the regulation of the thrust vector (sit) into the thrust chamber nozzle. On the other side, sit is regulated by flow management and does not require moving components. Overall, cod predictions were found to be in close agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Airfoil is an aerodynamic structure that is widely used in aircraft wings, UAVs, and fluid engines such as pumps, compressors, and turbines. The airfoil on the UAV wing is used to lift the UAV body where the pressure difference between the top and bottom of the airfoil causes the UAV to get a lift. Improving airfoil performance can be done in various ways, one of which is changing the angle of inclination in the airfoil range (swept angle). This is often seen in almost all types of commercial aircraft such as the Boeing 777 and Airbus 380. The method used in this study is a three-dimensional numerical simulation using Ansys 19.1 software. The specimens were Eppler 562 airfoil with a chord length of 200 mm, aspect ratio (AR) of 5, angle of attack 0°, 2°, 4°, 6°, 8°, 10°,12°,15°, 16°,17°,19°, and 20°. The variation of the swept-back used is angle Λ=0° (unswept), 15°, and 30°. Fluid flow is flowing air with the Reynolds number (Re)=2.34 × 104 in unsteady conditions. From this research, it was found that the variation of the swept-back will change the direction of flow to the wingtip and away from the wing root. This change in flow direction will reduce the occurrence of a vortex-shaped streamline that occurs on the unswept or rectangular wing. However, the variation of the swept-back will increase the tip vortex. [ABSTRACT FROM AUTHOR]

An experimental study of the influence of the boundary layer suction distributed over the surface on the stationary disturbance generated upstream was carried out on a straight wing model at subsonic flow velocities. A localized three-dimensional roughness element was used to excite stationary disturbances near the leading edge. Using the hot-wire method, quantitative data were obtained on the structure of the flow behind the roughness downstream with and without suction. It was shown that using the technique of suction of the boundary layer, inside which a stationary disturbance propagates, it is possible to reduce the level of pulsations by 4.6 times. [ABSTRACT FROM AUTHOR]

Basing on the solution of the Navier-Stokes equations and using the k-ω SST turbulence model, a numerical simulation of the supersonic flow in an air intake with an internal channel of a rectangular cross section was performed for the case when the shock wave generated by the inlet cowl interacted with the turbulent boundary layer on the inner surfaces of the channel. The three-dimensional configuration consisted of a convergent entrance section and a throat of a constant cross-sectional area is considered. Flow parameters at the entrance of the air intake were set taking into account the boundary layer developing on a pre-compression surface of an aircraft in front of the inlet. Two variants of the internal channel geometry were considered: firstly, when the lower surface of the channel was plane and, secondly, when this surface was arranged with longitudinal ribs. Numerical simulation of the three-dimensional flow was performed at the free-stream Mach number M = 4. [ABSTRACT FROM AUTHOR]

Some new analytical results in 3DBL theory are reviewed and discussed. Considered problems include: the perturbation theory for three-dimensional flows, singularities in solutions of 3DBL equations and corresponding real flow structures, new models for the symmetric flow instability over thin bodies and studies of the control possibility, analyses of distinctive features of hypersonic flows on flat blunted bodies and corresponding physical phenomena. Applications of the theory to study viscous flow characteristics of real objects (aircraft wings, fuselages and others) are considered. [ABSTRACT FROM AUTHOR]

The problem of calibration of semi-empirical eN-method for prediction of laminar-turbulent transition in three-dimensional boundary layers is discussed. A high-resolving panoramic experimental technique to estimate the onset and length of the transition for aerodynamic applications is proposed and described. The position of laminar-turbulent transition is estimated also using the developed techniques for computing three-dimensional laminar-turbulent flow at a swept wing using an original transition module developed on the basis of the author's software bundle LOTRAN 3, the module being integrated into ANSYS Fluent. [ABSTRACT FROM AUTHOR]

The aim of this study is to apply Computational Fluid Dynamics (CFD) to optimize the contact tanks used for the disinfection process within water treatment plants. Numerous studies have shown that by changing the geometric characteristics of traditional "serpentine" tanks used for disinfection, it is possible to reduce short circuits and the development of low speed areas. These construction measures can therefore bring the flow closer to the ideal plug-flow condition and increase the disinfection efficiency. In particular, this study reports on results from Large Eddy Simulation (LES) used to simulate three-dimensional turbulent flow and disinfectant transport in different contact tanks, suggesting that the tank and baffle's geometry can significantly influence the process. [ABSTRACT FROM AUTHOR]

The heat exchanger system is one of the important components for many of the non-conventional power-producing system. These heat exchanger systems may be used effectively as absorbing and storing heat from say solar ducts/panels, exchanging the heat for solar assisted refrigeration systems, etc. However, developing a compact and high effective heat exchanger system is a challenge. It has also been seen that the heat transfer will be more for the turbulent flows or flows where mixing dominates with higher heat transfer coefficient values. In this paper, we have developed a small concentric annulus heat exchanger having a helical flow passage. This compact heat exchanger is utilized to replace the electric heat source supplied to the Electrolux refrigerator. The helical flow is produced by providing a helical metal baffle between the two concentric annulus pipes. The working medium through the helixchanger is nanoparticle blended with water. CuO and Al2 O3 are the two popularly nanomaterials are mixed with water and their effectiveness is compared. The discrete phase model (DPM) based numerical simulation of the three-dimensional flow through helixchangers is presented here. The DPM exactly mimics the actual flow scenarios where nanoparticles are injected/blended along with the flowing fluid and expected to provide a realistic solution. The flow-through helixchanger is simulated for various Reynolds numbers and corresponding pressure drop, the average heat transfer coefficient is studied and presented here. Due to added nanomaterial in the working medium, the heat transfer is found to be increased by 25-30% as compared to without nanomaterial blend. Also, there are negligible pressure changes hence indicating the same pump power requirements for pumping. At the last, the results are validated with experimental values and their matching is found good. [ABSTRACT FROM AUTHOR]

The paper discusses a new exact solution of the Oberbeck-Boussinesq system describing the three-dimensional flow of a viscous incompressible fluid layer. Quadratic heating is determined at one of the boundaries of the fluid layer, along two mutually perpendicular horizontal directions. A particular exact solution of the boundary value problem is analyzed for the obtained velocity and temperature fields. The possibility of the occurrence of counterflow regions inside the fluid layer is reported. [ABSTRACT FROM AUTHOR]

A new exact solution of the Oberbeck-Boussinesq system describing the three-dimensional flow of a layer of a viscous incompressible fluid is discussed. Quadratic heating along two mutually perpendicular horizontal directions and the no-slip condition are determined at one of the boundaries of the fluid layer. At the other boundary, the quadratic law of pressure change along two mutually perpendicular horizontal directions is specified. A particular exact solution of the boundary value problem is analyzed for the obtained velocity and temperature fields. The possibility of the appearance of counterflow areas inside the fluid layer is shown. [ABSTRACT FROM AUTHOR]

The results of numerical simulation of the detonation wave interaction with a reacting supersonic flow in a three-dimensional setting are presented. The cavity was used as a flame stabilizer. A comparison of the flow fields for different positions of the detonation tube is shown for two-dimensional and three-dimensional calculations. It was revealed that the lower position of the detonation wave initiator is more preferable for the channel configuration under consideration. The necessity of changing the geometry of the combustion chamber and/or fuel supply system has been established. [ABSTRACT FROM AUTHOR]

Many liquid systems, including polymeric and biopolymer materials, often exhibit a slip anomaly near a solid surface. Such effect leads to a violation of the hypothesis of sticking on the wall and the need to indicate the corresponding boundary conditions. This anomalous behavior of materials in a viscous state (suspensions, solutions and melts) on solid surfaces requires a comprehensive study of both the rheological properties and the calculation of flow parameters and characteristics in the nodes of the process equipment. First, there are quite complex problems in determining the rheological characteristics of a material in accordance with viscometric studies. The next stage is associated with specific problems on the motion of a fluid, which exhibits slippage on solid surfaces and in the direct use of the slip velocity as boundary conditions. This work is to determine the slip velocity on the wall, which is usually a function of the wall stress, geometrical dimensions and temperature. The dependence of the sliding velocity on the wall on these factors can be found from viscometric measurements. Further, the case of a plane Poiseuille flow was considered, taking into account polymer slippage at the boundary. The system of equations of the modified Vinogradov and Pokrovskii model describes a non-parabolic velocity profile in the interspace between parallel plates, which is confirmed by experimental data. The dependences obtained can be used to study more complex flows. This is illustrated by the example of the calculation of the three-dimensional velocity profile of a nonlinear viscoelastic fluid in a channel with a square cross section. [ABSTRACT FROM AUTHOR]

This paper presents results of numerical and experimental study of three-dimensional flow in a model of the femoral artery graft with a spiral ridge on the wall. The swirl number of the flow formed in the graft corresponds to a typical value reported for healthy arteries. The flow patterns obtained for the spiral-ridge graft are compared with the case of flow in a graft with no ridge. It has been revealed that in the swirling flow case, wall shear stresses in the suture zone are considerably higher and the oscillatory shear index is lower than in the standard graft with no spiral ridge. The found swirl-induced changes in flow characteristics can result in a significant reduction of the graft occlusion rate. An increase in the graft pressure drop caused by the flow swirl generation was the one evaluated as hemodynamically insignificant. [ABSTRACT FROM AUTHOR]

The paper explores two-dimensional water course, flowing from non-pressure rectangular or circular-shaped pipe to the wide horizontal discharge channel. A broad range of solutions for the flow function has been obtained. To simplify the problem, a real three-dimensional flow is modelled as a two-dimensional routine water course through eliminating velocities and accelerations of liquid particles in the direction, perpendicular to the flow motion plan. To describe the law of the water course motion, L. Euler’s equations for ideal fluid, considering continuity equations and Bernoulli’s equations, are used. A linear system of equations of moving in the plane of velocity hodograph for potential function and flow function, and the 2nd order linear differential equation for the flow function are inferred from the Euler’s equations. The equation for flow function is reduced to a hypergeometric one, and, thus, a whole spectrum of solutions for the flow function is obtained. The obtained relationships between distribution of velocities and geometry of water course provide accuracy beyond that, which is known when using the previous methods, both in terms of values of velocities, and geometry of flow borderlines. [ABSTRACT FROM AUTHOR]

Airfoil is an aerodynamic model that is widely used both on aircraft wings, Unmanned Aerial Vehicle (UAV) and fluid machines such as pumps, compressors, and turbines. The airfoil on aircraft wings with the resulting lift force is used to lift the entire aircraft. Therefore, the researchers concentrate more on wing modification so that the resulting lift is more optimal. Increased performance of the airfoil on the wing can be done in various ways, one of which is adding a winglet to reduce drag. It is hoped that a large enough lift and drag ratio will improve aircraft performance. This research was conducted by numerical simulation using Ansys 19.0. with turbulent model k-ω SST. The velocity flow rate used is 10 m / s (Re = 2.3 × 104) with α = 0°, 2°, 4°, 6°, 8°, 10°, 12°, 15°, 16°, 17°, 19° and 20°. The test model is an Eppler 562 (E562) airfoil with and without a winglet. From this study, tip vortex was seen in plain wings, forward wingtip fence and rearward wingtip fence with lower speeds. In the area that has been separated (wake) which is indicated by a lower speed in the three configurations × = 1c. In the z = 1.5c area, it is shown that there is a pathline pattern difference between the three configurations. It is shown that the influence of the three-dimensional flow on the rearward wingtip fence where there is a higher velocity in the upper surface area. In the trailing edge, z = 1.9 shows that there is a pathline from the lower surface to the upper surface in the plain wing and rearward wingtip fence. [ABSTRACT FROM AUTHOR]

A new experimental technique of panoramic determination of the position of the laminar-turbulent transition in three-dimensional boundary-layer flows with a thermal imaging camera is described. It is shown that it is suitable for parametric measurements of the transition providing a sharp location of the transition at both low and high degrees of free-stream turbulence. [ABSTRACT FROM AUTHOR]

A numerical study of the effects of disturbances on the interaction of a transitional supersonic flat-plate boundary layer with an incident oblique shock has been carried out. Direct numerical simulation of the transitional boundary layer on a flat plate is performed by solving the Navier–Stokes equations using two different CFD codes: parallel code CFS3D and hybrid parallel code HyCFS. The simulation is carried out in a three-dimensional computational domain at free-stream Mach number M = 1.45, which corresponds to the conditions of the experiments. At first stage, the transitional boundary layer is computed without an incident shock wave. Development of the disturbances introduced at the inflow boundary causes formation of a secondary flow in the form of three-dimensional longitudinal vortex structures that leads to the laminar-turbulent transition farther downstream. At the second stage, boundary conditions corresponding to the parameters behind an oblique shock are specified on a part of the upper boundary of the computational domain. As a result of the interaction of the boundary layer with an incident shock in the reflection region, a separation zone is formed. The presence of large-scale eddies developing in the boundary layer causes significant oscillations of the separation zone. Due to the shock wave boundary layer interaction the laminar-turbulent transition shifts upstream towards the separation region. [ABSTRACT FROM AUTHOR]

The investigations presented focus on the features of calculating the characteristics of vortex formation and decay processes that cause aerodynamic buffet loads acting on elements of aircraft at incompressible subsonic flow. Analysis of stability and numerical dissipation of differencing schemes implemented in OpenFOAM package has been carried out. Based on the obtained results, modification of some differencing schemes has been done. An algorithm for combining RANS and LES approaches for modelling turbulent flows has been briefly presented. A series of calculations of three-dimensional flow around an aircraft considering airbrake has been carried out. [ABSTRACT FROM AUTHOR]

The present work is a numerical simulation of flow over buildings. The numerical simulation was carried out using an open source Computational Fluid Dynamics (CFD) tool called Open FOAM®. The Reynolds Averaged Navier Stokes Equations (RANS) was solved along with a two-equation turbulent closure. The solutions from the numerical simulations are post-processed with open source software namely Paraview which is based on Visualisation Tool Kit (VTK). Effect of flow over buildings is described in terms of contours of velocity. Further, the same data is processed with Line Integral Convolution (LIC) to reveal three-dimensional flow properties on a plane parallel to the inlet flow. The streamlines are visualised in addition to the LIC and velocity contours. The post processed results reveal the real flow physics with just LIC alone or with the help of streamlines and contours. [ABSTRACT FROM AUTHOR]

The present work is a numerical simulation of flow over buildings. The numerical simulation was carried out using an open source Computational Fluid Dynamics (CFD) tool called Open FOAM®. The Reynolds Averaged Navier Stokes Equations (RANS) was solved along with a two-equation turbulent closure. The solutions from the numerical simulations are post-processed with open source software namely Paraview which is based on Visualisation Tool Kit (VTK). Effect of flow over buildings is described in terms of contours of velocity. Further, the same data is processed with Line Integral Convolution (LIC) to reveal three-dimensional flow properties on a plane parallel to the inlet flow. The streamlines are visualised in addition to the LIC and velocity contours. The post processed results reveal the real flow physics with just LIC alone or with the help of streamlines and contours. [ABSTRACT FROM AUTHOR]

This paper presents a comparative study of the movement of various rigid bodies through an air tunnel for both two and three-dimensional flow problems. Three kinds of objects under investigation are in the form of box, ball and wedge shape. The investigation was carried out through the use of a commercial CFD software, named Fluent, in order to determine aerodynamic forces, act on the object as well as to track its movement. Adopted numerical scheme is the time-averaged Navier-Stokes equation with κ -- ε as its turbulence modeling and the scheme was solved using the SIMPLE algorithm. Triangular elements grid was used in 2D case, while tetrahedron elements for 3D case. Grid independence studies were performed for each problem from a coarse to fine grid. The motion of an object is restricted in one direction only and is found by tracking its center of mass at every time step. The result indicates the movement of the object is increasing as the flow moves down stream and the box have the fastest speed compare to the other two shapes for both 2D and 3D cases. [ABSTRACT FROM AUTHOR]

In this paper, the problem of a steady laminar three-dimensional stagnation point boundary layer flow on a permeable moving surface with anisotropic slip in a viscous fluid is investigated. A similarity transformation reduces the governing system of nonlinear partial differential equations into the ordinary (similarity) differential equations. The resulting equations are then solved numerically by using the bvp4c function in Matlab. The effects of surface mass transfer parameter, slip parameter, ratio of slip factors and moving parameter on the fluid flow characteristics are presented in the forms of tables and figures and are discussed in details. [ABSTRACT FROM AUTHOR]

This paper focuses on a steady free convection in the stagnation point region of a three-dimensional body that is immersed in a nanofluid. A kind of similarity transformations is used so that the governing equations describing the conservation of total mass, momentum, thermal energy, nanoparticles are reduced to a set of fully coupled ordinary differential equations. We proposed a novel numerical technique by combining the homotopy analysis method(HAM) with the finite difference method to solve this problem. Based on this technique, we obtain the solutions for those ODEs. The proposed method inherits the advantage of the homotopy analysis method to solve strong nonlinear problem, and it can greatly improve the computational efficiency of the homotopy analysis method. [ABSTRACT FROM AUTHOR]

The three-dimensional flow and heat transfer of a nanofluid over a stretching sheet is studied. Numerical solutions are obtained using the boundary value problem solver bvp4c in MATLAB. It is noted that the results obtained for three-dimensional flow are similar to the results obtained in most two-dimensional flow problems. The suction and stretching parameter decrease the skin friction coefficient. On the other hand, increasing the stretching parameter is to increase the local Nusselt number. Although Biot number encourages the heat transfer rate at the surface, increasing thermophoresis parameter and Brownian motion parameter causes the local Nusselt number to decrease. [ABSTRACT FROM AUTHOR]

In this study, a numerical investigation on the unsteady three-dimensional boundary layer flow of a viscous fluid past a permeable stretching/shrinking sheet is considered. Similarity transformation is employed to reduce the governing system of nonlinear partial differential equations into the ordinary (similarity) differential equations. These equations are then solved numerically by using a shooting method. Both stretching and shrinking cases are considered. Effects of the unsteadiness parameter, stretching/shrinking parameter, mass suction parameter and ratio of the surface velocity gradients along the vertical y- and horizontal x- directions are presented and discussed in detail. The numerical results show that for the shrinking case, the skin friction coefficient and the velocity boundary layer thickness increase with increasing unsteadiness parameter, while the skin friction coefficient decreases and the velocity boundary layer thickness increases with increasing ratio of the surface velocity gradients. The results also show that dual solutions exist for both cases of stretching and shrinking sheet. [ABSTRACT FROM AUTHOR]

This article presents a numerical investigation on the three-dimensional boundary layer flow and heat transfer of a copper, Cu-water nanofluid in the vicinity of a permeable shrinking flat surface in an otherwise quiescent fluid. It is assumed that the nanofluid is incompressible and the flow is laminar. The nanofluid mathematical model proposed by Tiwari and Das is used in which the effect of the nanoparticle volume fraction is considered. The governing nonlinear partial differential equations are transformed into a system of nonlinear ordinary differential equations using a similarity transformation which is then solved numerically using the shooting method. The numerical results for the skin friction coefficient and the local Nusselt number as well as the velocity and temperature profiles are obtained, presented and discussed for a range of various values of the governing parameters. [ABSTRACT FROM AUTHOR]

Increasing attention is paid on wet gas flow measurement with V-Cone meter in the production of natural gas. Annular-mist flow is a common flow regime in the wet gas flow metering. Knowledge of the annular-mist flow such as the distributions of the pressure, the droplet and the liquid film in the V-Cone meter is critical to improve the wet gas measurement model. In this paper, a numerical method based on a three-fluid closure model of film, droplet and gas was developed to simulate the annular-mist wet gas flow in the V-Cone meter. The method agreed well with the existing correlation and the relative error of simulation data is less than ±2.5%. The distributions of the droplet, liquid film and static pressure in a V-cone meter and the results on different flow conditions were simulated with the present method. The simulations showed that under the adjustment of the V-Cone element, the droplets moved in a straight path close to the wall after the throat section and a liquid jet was formed. It continues through the diffuser and reattaches to the wall. Some droplets will re-coalescence in the downstream of the V-Cone. It was found that little droplet was entrained in the back of the V-Cone, which was benefit for obtaining the low pressure. The results of the liquid film distribution showed that the liquid film thickness on the pipe wall and the cone body was affected by both the geometry of the V-Cone and the area and strength of the low pressure domain. The pressure in the low pressure domain decreased with the liquid and gas velocity increasing, and the gas-to-liquid viscosity ratio had little effects on the pressure distribution. The downstream low pressure port justifiably locates at six or more pipe diameters downstream of the cone back face for the present V-Cone meter. [ABSTRACT FROM AUTHOR]

We present a fast synchrotron X-ray tomography study of the packing structures of rods under tapping. Utilizing the high flux of the X-rays generated from the third-generation synchrotron source, we can complete a tomography scan within several seconds, after which the three-dimensional (3D) packing structure can be obtained for the subsequent structural analysis. Due to the high-energy nature of the X-ray beam, special image processing steps including image phase-retrieval has been implemented. Overall, this study suggests the possibility of acquiring statistically significant static packing structures within a reasonable time scale using high-intensity X-ray sources. [ABSTRACT FROM AUTHOR]

A three-dimensional (3D) capillary water contact model was established and implemented into the Distinct Element Method (DEM) to investigate the mechanical behavior of unsaturated granular materials. 3D assemblies of spheres were examined under triaxial compression loading with focus on the effects of suction and initial compaction density on macro-behavior (e.g. strength and deformation) and micro-structure (e.g. stress-induced fabric anisotropy). The fabric was described by the directional distribution of contact-normal and transient particle rotation axis. The DEM results show that the cohesion of the material increases with the suction and is independent of the initial compaction density while the peak friction angle only depends on the density. The loading can change the distribution of contacts in a specimen by increasing the proportion of contacts in the loading direction. Particles are statistically more prone to rotate about axes in the plane orthogonal to the loading direction when the specimen is contractive, which is followed by more prominent rotation about the loading direction when the specimen is dilative. The dense assemblies exhibit greater anisotropy than the loose ones for the two defined fabrics. [ABSTRACT FROM AUTHOR]

A hybrid N-S/DSMC method is presented and applied to solve the three-dimensional hypersonic transitional flows by employing the MPC (modular Particle-Continuum) technique based on the N-S and the DSMC method. A sub-relax technique is adopted to deal with information transferring between the N-S and the DSMC. The hypersonic flows around a plate and a blunt cone under different Kn numbers are simulated by using the hybrid N-S/DSMC method. The present computations are found in good agreement with other experimental results. The present method provides an efficient way to predict the hypersonic aerodynamics in near-continuum transitional flow regime. [ABSTRACT FROM AUTHOR]

In this work a three phase 3D mathematical model was developed using the Volume Of Fluid (VOF) algorithm, which is able to accurately describe the cavity geometry and size as well as the liquid flow patterns created when a gas jet impinges on a two phase liquid free surface. These phenomena are commonly found in steelmaking operations such as in the Electric Arc Furnace (EAF) and the Basic Oxygen Furnace (BOF) where oxygen jets impinge on a steel bath and they control heat, momentum and mass transfer. The cavity formed in the liquids by the impinging jet depends on a force balance at the free surface where the inertial force of the jet governs these phenomena. The inertial force of the jet and its angle play important roles, being the lowest angle the best choice to shear the bath and promote stronger circulation and better mixing in the liquids. [ABSTRACT FROM AUTHOR]

This paper presents a methodology for time trending space cryocooler technology (cold tip temperatures, cooling loads). This methodology analyzes historical trends starting from the 1960s across three dimensions (time, specific power, and temperature). It can be used as a basis to assess whether future industrial capability may satisfy future program technology needs. [ABSTRACT FROM AUTHOR]