Profiles Of Velocity Components Research Articles

Recent Development of Heat and Mass Transport in the Presence of Hall, Ion Slip and Thermo Diffusion in Radiative Second Grade Material: Application of Micromachines.

This article describes the incompressible two-dimensional heat and mass transfer of an electrically conducting second-grade fluid flow in a porous medium with Hall and ion slip effects, diffusion thermal effects, and radiation absorption effects. It is assumed that the fluid is a gray, absorbing–emitting but non-scattering medium and the Rosseland approximation is used to describe the radiative heat flux in the energy equation. It is assumed that the liquid is opaque and absorbs and emits radiation in a manner that does not result in scattering. It is considered an unsteady laminar MHD convective rotating flow of heat-producing or absorbing second-grade fluid across a semi-infinite vertical moving permeable surface. The profiles of velocity components, temperature distribution, and concentration are studied to apply the regular perturbation technique. These profiles are shown as graphs for various fluid and geometric parameters such as Hall and ion slip parameters, radiation absorption, diffusion thermo, Prandtl number, Schmidt number, and chemical reaction rate. On the other hand, the skin friction coefficient and the Nusselt number are determined by numerical evaluation and provided in tables. These tables are then analysed and debated for various values of the flow parameters that regulate it. It may be deduced that an increase in the parameters of radiation absorption, Hall, and ion slip over the fluid region increases the velocity produced. The resulting momentum continually grows to a very high level, with contributions from the thermal and solutal buoyancy forces. The temperature distribution may be more concentrated by raising both the heat source parameter and the quantity of radiation. When one of the parameters for the chemical reaction is increased, the whole fluid area will experience a fall in concentration. Skin friction may be decreased by manipulating the rotation parameter, but the Hall effect and ion slip effect can worsen it. When the parameter for the chemical reaction increases, there is a concomitant rise in the mass transfer rate.

Hall Current’s Impact on Ionized Ethylene Glycol Containing Metal Nanoparticles Flowing Through Vertical Permeable Channel

From engineering and industrial perspectives, the transportation of non-Newtonian nanofluids in a magnetic environment has become an emergent research area. Motivated by its incessant boosting applications in advanced industries and technologies, a mathematical model is proposed to address the consequences of Hall currents on an unsteady magnetohydrodynamic flow of a partially ionized ethylene glycol (EG) transporting silver nanoparticles (Ag-NPs) through a vertical permeable channel subject to a strong transverse magnetic field, Darcy’s resistance, and thermal radiation. Ethylene glycol (EG) is considered as the base fluid. A uniform suction or injection is imposed at the channel walls. The thermal radiation effect is embraced in the energy equation. Closed-form solutions of the leading dimensionless equations are determined. The impacts of emerging parameters upon the flow profiles are examined and physically argued via profile graphs. The wall shear stresses and the rate of heat transfer are computed numerically, and numerical data on varying thermo-physical parameters are documented in tables. After a detailed analysis, it is documented that an augmentation in Hall parameter gives rise to the profiles of velocity components and shear stresses. Enlarging Casson parameter and Darcy number both urge the magnitude of the velocity components. A graphical comparison is provided for EG and Ag-EG nanofluid. The relatively lowest temperature is noted for Ag-EG nanofluid in comparison with EG. The current model may be featured in industrial processes, food processing, intelligent lubrication technology, high-energy cooling systems, auto cooling machines, etc. This study is very prolific to the analysts to understand the dynamics and heat transfer characteristics of non-Newtonian nanofluids through a straight channel subject to a strong magnetic field.

Optimization of cooling of three radiant heat source inside an inclined porous medium using particle swarm optimization

In this study, an optimization of the maximum cooling of three radiant heat sources inside a closed square porous environment is performed. Three radiant-heat sources are cooled by airflow in a porous medium with an inclination angle. It is applied in the cooling of electronic equipment inside laptop computers. The cooling phenomenon is a function of five independent variables, such as the length of heat source, radiation parameter, Darcy number, the angle of inclination of a porous medium, and Rayleigh number. Differential equations are solved using the finite-difference approach. And those are solved by the Gauss-Seidel approach. Simulation is a numerical solution of the vorticity–stream equations. Coding is done in MATLAB software. And it is obtained the maximum objective function using the algorithm of particle swarm optimization. Cooling simulations are performed by drawing flow lines, constant temperature lines, dimensionless velocity component profiles, local Nusselt numbers, and mean Nusselt numbers. The main goal is to find the highest cooling rate in different amounts of five independent variables. The flow is in the laminar flow regime, and inclination angles are between 0 to 360°. The present study is the first study on the numerical solution of the cooling of three radiant-heat sources with an inclination angle by the porous media-filled square environment. And it is developed from the cooling of hot radiation walls problems in an inclined enclosure with constant temperature local radiant heat sources. This investigation showed the flow lines and their direction are influenced by the inclination angle of the porous medium strongly, and the maximum heat transfer is achieved at an angle of inclination of zero degrees. This investigation showed at the Darcy number, 0.001, and the radiation parameter, 1. The maximum and minimum Nusselt number is obtained for the inclination angle 60 and 180°, respectively.

Dynamics in a stellar convective layer and at its boundary: Comparison of five 3D hydrodynamics codes

Our ability to predict the structure and evolution of stars is in part limited by complex, 3D hydrodynamic processes such as convective boundary mixing. Hydrodynamic simulations help us understand the dynamics of stellar convection and convective boundaries. However, the codes used to compute such simulations are usually tested on extremely simple problems and the reliability and reproducibility of their predictions for turbulent flows is unclear. We define a test problem involving turbulent convection in a plane-parallel box, which leads to mass entrainment from, and internal-wave generation in, a stably stratified layer. We compare the outputs from the codes FLASH, MUSIC, PPMSTAR, PROMPI, and SLH, which have been widely employed to study hydrodynamic problems in stellar interiors. The convection is dominated by the largest scales that fit into the simulation box. All time-averaged profiles of velocity components, fluctuation amplitudes, and fluxes of enthalpy and kinetic energy are within ≲3σ of the mean of all simulations on a given grid (1283 and 2563 grid cells), where σ describes the statistical variation due to the flow’s time dependence. They also agree well with a 5123 reference run. The 1283 and 2563 simulations agree within 9% and 4%, respectively, on the total mass entrained into the convective layer. The entrainment rate appears to be set by the amount of energy that can be converted to work in our setup and details of the small-scale flows in the boundary layer seem to be largely irrelevant. Our results lend credence to hydrodynamic simulations of flows in stellar interiors. We provide in electronic form all outputs of our simulations as well as all information needed to reproduce or extend our study.

Low Reynolds number backward-facing step flow calculation and adaptive mesh application

In this paper, a study of the flow behavior in a backward facing step in low Reynolds number range from 100 to 800 is conducted using COMSOL Multiphysics®. The k-ε turbulence model is takne into account. The investigation starts from a standard mesh and then refine the standard mesh using an adaptive mesh refinement method. The horizontal and vertical velocity component profiles, pressures and the velocity quiver are shown on the refined meshes. The overall characteristics of separating shear layer, the flow behavior of the transverse vortices in the main flow and a reattachment length on a lower side wall is presented. The effectiveness of the adaptive mesh refinement method is verified and the method could be expected as a CAE analysis tool for industrial utilization.

Influence of Chemical Reaction and Arrhenius Activation Energy on Hydromagnetic Non-Darcian Casson Nanofluid Flow with Second-Order Slip Condition

This article investigates the combined effect of second-order velocity slip, Arrhenius activation energy and binary chemical reaction on reactive Casson nanofluid flow in a non-Darcian porous medium. The governing equations of the problem were first non-dimensionalized and later reduced to ordinary nonlinear differential equations by adopting a similarity transformation. The emerging nonlinear boundary value problem was solved by using Galerkin weighted residual method (GWRM). The obtained results were compared with those found in the literature to validate our method. The impact of pertinent parameters on the velocity component, temperature distribution and concentration profile are presented using graphs and were discussed. The computational results show that an increase in second order slip parameter significantly results to an increase in the temperature as well as nanoparticle concentration profiles, while it reduces the velocity profile.

Comparative analysis of the slipstream of different nose lengths on two trains passing each other

The scenario of high-speed trains (HSTs) passing each other is usually encountered, which causes aerodynamic effects such as high slipstream velocity and strong aerodynamic loads, leading to trackside worker injuries, equipment fatigue damage, and snake-like train motions. This study used a three-dimensional, compressible, improved delayed detached eddy simulation (IDDES) method based on an SST k-ω turbulence model to research the turbulent flow around the train bodies generated by two trains passing each other in the open air. An overset grid method was utilised to tackle the moving boundary problem. The numerical results were firstly verified by comparison with the results of a moving model test. Then, temporal and spatial evolution of the flow field was analysed in detail based on a 4 ​m nose length model. The results show that the process of intersecting has a pronounced effect on the vortices as well as the boundary layer at the bottom of train side. The peaks of three slipstream velocity component profiles decrease as the distances from the centre of the track (COT) and the top of the rail (TOR) increase. Finally, considering three different nose lengths (4 ​m, 7 ​m, and 9 ​m), the differences in the instantaneous flow structures, slipstream profiles, and aerodynamic coefficients were elucidated. The longer nose lengths were found to reduce the scale and strength of the counter-rotating vortices, thereby lowering the maximum slipstream peaks in the wake. The slipstream resultant velocity at trackside height for the 7 ​m nose length case is 22.2% lower and 9.2% higher than the corresponding values for the 4 ​m and 9 ​m nose length cases, respectively. The side force coefficient is also influenced by the nose length, with the stronger effect being exerted on the head car and tail car than on the middle car.

Hall and ion slip current’s impact on magneto-sodium alginate hybrid nanoliquid past a moving vertical plate with ramped heating, velocity slip and Darcy effects

PurposeThe purpose of this study is to analyze an unsteady MHD Darcy flow of nonNewtonian hybrid nanoliquid past an exponentially accelerated vertical plate under the influence of velocity slip, Hall and ion slip effects in a rotating frame of reference. The fluids in the flow domain are assumed to be viscously incompressible electrically conducting. Sodium alginate (SA) has been taken as a base Casson liquid. A strong uniform magnetic field is applied under the assumption of low magnetic Reynolds number. Effect of Hall and ion-slip currents on the flow field is examined. The ramped heating and time-varying concentration at the plate are taken into consideration. First-order homogeneous chemical reaction and heat absorption are also considered. Copper and alumina nanoparticles are dispersed in base fluid sodium alginate to be formed as hybrid nanoliquid.Design/methodology/approachThe model problem is first formulated in terms of partial differential equations (PDEs) with physical conditions. Laplace transform method (LTM) is used on the nondimensional governing equations for their closed-form solution. Based on these results, expressions for nondimensional shear stresses, rate of heat and mass transfer are also determined. Graphical presentations are chalked out to inspect the impacts of physical parameters on the pertinent physical flow characteristics. Numerical values of the shear stresses, rate of heat and mass transfer at the plate are tabulated for various physical parameters.FindingsNumerical exploration reveals that a significant increase in the secondary flow (i.e. crossflow) near the plate is guaranteed with an augmenting in Hall parameter or ion slip parameter. MHD and porosity have an opposite effect on velocity component profiles for both types of nanoliquids. Result addresses that both shear stresses are strongly enhanced by the Casson effect. Also, hybrid nanosuspension in Casson fluid (sodium alginate) exhibits a lower rate of heat transfer than usual nanoliquid.Social implicationsThis model may be pertinent in cooling processes of metallic infinite plate in bath and hybrid magnetohydrodynamic (MHD) generators, metallurgical process, manufacturing dynamics of nanopolymers, magnetic field control of material processing, synthesis of smart polymers, making of paper and polyethylene, casting of metals, etc.Originality/valueThe originality of this study is to obtain an analytical solution of the modeled problem by using the Laplace transform method (LTM). Such an exact solution of nonNewtonian fluid flow, heat and mass transfer is rare in the literature. It is also worth remarking that the influence of Hall and ion slip effects on the flow of nonNewtonian hybrid nanoliquid is still an open question.

Flow of a viscous fluid over an infinite rotating and porous disk with stretching (shrinking) effects

A viscous flow is maintained over a porous and rotating disk. The porous disk is stretched (shrunk) with the non-uniform velocity in the radial direction. Note that the viscous fluid is injected (blown) normally with non-uniform velocity. The study is under taken by considering the combined and individual effects of injection (suction), stretching (shrinking) and rotation. The kinematics properties associated with the disk are depending upon the radial coordinate. The governing partial differential equations (PDE’s) are simplified and transformed into a new system of DE’s. The set of boundary value ODE’s is solved with the help of a numerical method. The transformed equations (presented over here) are new and to the best of authors knowledge, the equations are not published in literature. In particular cases, the modeled equations may reduce to the classical problems of rotating disk flows. The previous models of rotating disk flows with or without porosity and stretching (shrinking) effects are summarized into a single model. For fixed value of the governing parameters and different sizes of "infinity", no increase/decrease in the thickness of boundary layer is seen but the profiles of velocity components and pressure are significantly changed with the different levels of "infinity".

HALL EFFECT ON HEAT TRANSPORT OF MAGNETIZED Cu-ENGINE OIL OVER A ROTATING SLIPPING DISK WITH CONVECTIVE HEATING IN A POROUS SPACE

The purpose of this article is mainly to explore the effect of Hall currents and slip conditions on the unsteady magneto-hydrodynamic flow and heat transfer of electrically conducting copper-engine oil (non-Newtonian Casson nanoliquid) over a rotating porous disk with hydrodynamic slip and convective heating in a porous space of Darcy resistance. The Casson model is used to describe the rheology of the non-Newtonian fluid in this study. Non-Newtonian Casson nano-liquid is engineered by dispersing copper (Cu) nanoparticles in engine oil (EO). The disk is subjected to convective boundary conditions and the effect of viscous and Joule dissipations are taken into account in this analysis. The present physical model is analyzed under the influence of strong Lorentz force to investigate the effect of the Hall current on the flow behavior. An exact solution is established for the governing momentum equation by employing the Laplace transform method. The MATLAB built-in function pedpe is used to numerically solve the nonlinear energy equation. The impact of significant parameters on the flow fields is analyzed by plotting graphs and tables and discussed in detail. The computations demonstrate that the Hall current generates substantial enhancement in the velocity component profiles and significantly elevates the temperature in the flow domain. The disk temperature is substantially reduced in the presence of suction. A comparative study of EO Casson and Cu-EO Casson nanoliquids is presented and interpreted. The inferences obtained from our investigation may effectively be used in disk cleaners, rotor-systemic manufacturing of magnetic nano-polymer coatings, fuel cell coatings, print ink, self-cleaning ceramics, cosmetics, etc.

Influence of applied magnetic field on mixed convective nanofluid flow past an exponentially stretching surface with roughness

In this analysis, the impact of the applied magnetic field and surface roughness on combined convection nanofluid flow past a stretching surface with roughness is investigated. The partial differential equations governing the flow fields are subjected to non-similar transformations. The transformed equations are quasi-linearised and then solved numerically using an implicit finite difference method. The non-similar profiles of flow velocity and diffusive components and also their gradients at the surface are computed and presented graphically. The results reveal that the velocity profile diminishes in the presence of magnetic field parameter, non-similarity variable and Eckert number. The temperature profile is enhanced in the presence of thermophoresis and magnetic parameters. The influence of a rough surface on profile gradients at the surface is analysed, and the impact of these is found to be prominent in case of the skin-friction coefficient. For a nanofluid, the Nusselt number is found to be reduced. Moreover, for liquid hydrogen, the Sherwood number is smaller as compared to that for liquid nitrogen.

Anisotropy of turbulent fluctuations of velocity and third-order moments in the near wake of a circular cylinder

Turbulent structure of the near wake behind a circular cylinder in a cross flow at Re = 3900 was studied experimentally. Instantaneous velocity vector fields in the wake were measured using Smoke Image Velocimetry (SIV). The profiles of velocity components, their RMS fluctuations and Reynolds stresses were compared with direct numerical simulation and experimental data obtained by other authors. The anisotropy of turbulent fluctuations in different zones of the wake was analyzed. Third-order moments of velocity fluctuations in the near wake behind the cylinder were measured for the first time ever.

Robust Nonparametric Methods of Statistical Analysis of Wind Velocity Components in Acoustic Sounding of the Lower Layer of the Atmosphere

Statistical analysis of the results of minisodar measurements of vertical profiles of wind velocity components in a 5–200 m layer of the atmosphere shows that this problem belongs to the class of robust nonparametric problems of mathematical statistics. In this work, a new consecutive nonparametric method of adaptive pendular truncation is suggested for outlier detection and selection in sodar data. The method is implemented in a censoring algorithm. The efficiency of the suggested algorithm is tested in numerical experiments. The algorithm has been used to calculate statistical characteristics of wind velocity components, including vertical profiles of the first four moments, the correlation coefficient, and the autocorrelation and structure functions of wind velocity components. The results obtained are compared with classical sample estimates.

Squeeze film dampers supporting high-speed rotors: Fluid inertia effects

This work represents closed-form analytical expressions for the operating parameters for short-length open-ended squeeze film dampers, including the lubricant velocity profiles, hydrodynamic pressure distribution, and lubricant reaction forces. The proposed closed-form expressions provide an accelerated calculation of the squeeze film damper parameters, specifically for rotordynamics applications. In order to determine the analytical solutions for the squeeze film damper parameters, the thin film equations for lubricant are introduced in the presence of the influence of lubricant inertia. Subsequently, two different analytical techniques, namely the momentum approximation method, and the perturbation method are applied to the thin film equations. Moreover, the solution for the lubricant flow equations are analytically determined to represent closed-form expressions for the hydrodynamic pressure distribution and the velocity component profiles in squeeze film dampers. Additionally, the expressions for the hydrodynamic pressure distribution are integrated over the journal surface, either numerically or analytically by using Booker’s integrals, to develop expressions for the fluid film reaction forces. Lastly, the developed squeeze film damper models are incorporated into simulation models in Matlab and Simulink®, and the results are compared against a well-established force coefficient model to verify the accuracy of the calculations. The results of the simulations verify the effect of the lubricant inertia components, namely the convective and temporal (i.e., unsteady) inertia components on the squeeze film damper dynamics, including hydrodynamic pressure distribution and fluid film reaction forces. Additionally, the simulation results suggest a close agreement between the proposed models and the results in the literature.

MHD Free Convection in a Partially Heated Open-Ended Square Cavity: Effect of Angle of Magnetic Field and Heater Location

A computational analysis based upon the kinetic, mesoscopic numerical tool is adapted for elucidating the buoyancy-driven convection in the square shaped open cavity having the partially active wall under the influence of the uniform magnetic field (B). A heater (size- half of the height of the cavity) is positioned along the vertical, no-slip wall of the cavity (while another vertical end is open to the atmosphere). Other regions of no-slip partially heated vertical wall, as well as top and bottom walls, are thermally insulated. The significance of heater location (bottom, middle and top), the angle of magnetic field (0°, 45° and 90°), Hartmann number (0–100) and Rayleigh number (103–105) on natural convection have been illustrated. The interpretation of results have been carried out by studying the streamlines, isotherms, centreline variation of temperature; velocity component profiles and Nusselt number (local, average). The dependence of the Nusselt number with the magneto-convective parameter is presented and discussed. Heat transfer rate increases with the angle of the magnetic field.

Two-Dimensional Modeling of a V-Shaped Turbulent Methane—Air Flame

A method for the simulation of turbulent combustion in the two-dimensional formulation is presented. A distinctive feature of this method is the assignment of the nonstationary profiles of velocity components at the input to the computational domain. The algorithms of artificial turbulence used for this purpose make it possible to set the necessary values of both the fluctuation intensity and the integral length scale of turbulence in the incoming flow. It is shown that this procedure describes with good accuracy the angle of the V-shaped flame front observed in the experiment, as well as the flame front thickening with increasing the distance from the flame stabilization point. The influence of various parameters of the incoming flow on the characteristics of the V-shaped flame was analyzed based on the developed method.

Steady Aerodynamic Characteristics of Two-Dimensional NACA0012 Airfoil for One Revolution Angle of Attack

Steady variations in aerodynamic forces and flow behaviors of two-dimensional NACA0012 airfoil were investigated using a numerical method for One Revolution Angle of Attack (AOA) at Reynolds number of $$10^{5}$$ . The profiles of lift coefficients, drag coefficients, and pressure coefficients were compared with those of the experimental data. The AERODAS model was used to analyze the profiles of lift and drag coefficients. Wake characteristics were given along with the deficit profiles of incoming velocity components. Both the characteristics of normal and reverse airfoil models were compared with the basic aerodynamic data for the same range of AOA. The results show that two peaks of the lift coefficients appeared at $$11.5{^{\circ }}$$ and $$42{^{\circ }}$$ and are in good agreement with the pre-stall and post-stall models, respectively. Counter-rotating vortex flows originated from the leading and trailing edges at a high AOA, which formed an impermeable zone over the suction surface and made reattachments in the wake. Moreover, the acceleration of inflow along the boundary of the vortex wrap appeared in the profile of the wake velocity. The drag profile was found to be independent of the airfoil mode, but the lift profile was quite sensitive to the airfoil mode.

CFD Analysis of 2D Unsteady Flow Past a Square Cylinder at Low Reynolds Numbers

A study of the behaviour of flow past a square cylinder for Reynolds numbers 10 and 20 is presented. Open source software Navier2d in Matlab is used in this study. The investigation starts from a uniform initial mesh and then refine the initial mesh using a mesh refinement method which was proposed based on both qualitative theory of differential equations and the finite volume method implemented in Navier2d. The horizontal and vertical velocity component profiles and pressures are shown on the once refined meshes. The comparisons between the profiles and pressures are conducted to show the variations from Reynolds number 10 to 20. The twice refined meshes are also presented and these refined meshes provide the information where the behaviour of flow is complex.

SIMULATION OF THE LID-DRIVEN CAVITY FLOW AT REYNOLDS NUMBERS BETWEEN 100 AND 1000 USING THE MULTI-RELAXATION-TIME LATTICE BOLTZMANN METHOD

The Multi-Relaxation-Time Lattice Boltzmann Method (MRT LBM) is used to numerically simulate the steady viscous incompressible flow in a lid-driven cavity. The simulations are performed for a range of Reynolds numbers between 100 and 1000. The simulation results include the flow streamlines which clearly show the location of the primary main vortex and the two side vortices, the horizontal and vertical velocity component profiles at different sections inside the cavity and the location of the vortices centers. The numerical results are compared against published results and show a perfect agreement. The simulation results are given for a range of Reynolds numbers not reported in the published literature. The presented results can be used for benchmarking other numerical methods in the reported range of the Reynolds number.

A Study of Lubricant Inertia Effects for Squeeze Film Dampers Incorporated into High-Speed Turbomachinery

This work proposes a numerical model that incorporates the effect of lubricant inertia on the hydrodynamic pressure distribution, fluid film reaction forces, and the fluid velocity component profiles for finite-length open-ended squeeze film dampers (SFDs). Firstly, the thin film flow equations for the SFD in presence of fluid inertia effects are introduced. Furthermore, a small first-order perturbation by means of the expressions for the fluid film velocity components and the lubricant pressure distribution that are expanded in power series of the squeeze film Reynolds number is applied to the flow equations. Subsequently the developed lubricant flow equations are solved to develop expressions for the velocity component profiles and the hydrodynamic pressure distribution in SFDs. The pressure expression is numerically solved by using Gauss–Seidel method with finite difference discretization. Moreover, the fluid film reaction forces are determined by numerically integrating the hydrodynamic pressure expressions over the journal surface. Additionally, the proposed pressure distribution expression and the numerical SFD forces are incorporated into a simulation model and the simulation results are compared with the existing models in the literature under different operating conditions, including eccentricity ratios and inertia effects (i.e., Reynolds numbers). The simulation results demonstrate the significant influence of both convective and temporal (i.e., unsteady) lubricant inertia terms on the SFD hydrodynamic pressure distribution and the fluid film reaction forces. Furthermore, the proposed SFD model is incorporated into a multi-mass flexible rotordynamic model to evaluate the effect of SFD fluid inertia on the mass unbalance induced steady-state vibrations of the rotor and the nodal transient orbits by implementing finite element method and transient modal integration with predictor–corrector solver. The results of the analysis demonstrate the significant effect of fluid inertia on the resonance frequencies of the rotor and the steady-state vibration amplitudes and the transient orbits at the resonance zone.