Flow Of Viscous Incompressible Fluid Research Articles

Isogeometric analysis for turbulent flow

The article is devoted to the simulation of viscous incompressible turbulent fluid flow based on solving the Reynolds averaged Navier–Stokes (RANS) equations with different k−ω models. The isogeometrical approach is used for the discretization based on the Galerkin method. Primary goal of using isogeometric analysis is to be always geometrically exact, independent of the discretization, and to avoid a time-consuming generation of meshes of computational domains. For higher Reynolds numbers, we use stabilization SUPG technique in equations for k and ω. The solutions are compared with the standard benchmark example of turbulent flow over a backward facing step.

Transient Heat and Mass Transfer of Micropolar Fluid between Porous Vertical Channel with Boundary Conditions of Third Kind

Abstract An investigation of heat and mass transfer characteristics of unsteady free convective flow of viscous incompressible micropolar fluid between the vertical porous plates in the presence of thermal radiation is carried out in the present work. The fluid is considered to be grey, absorbing–emitting but non scattering medium and the Cogley–Vincent–Gilles formulation is adopted to simulate the radiation component of heat transfer. The resulting system of equations is solved numerically with Crank–Nicolson implicit finite difference method. The effects of various physical parameters such as transient, micropolar parameter, radiation parameter, Reynolds number, Schmidt number, heat and mass transfer Biot numbers on the velocity, temperature and concentration field are discussed graphically.

A Numerical Investigation on the Onset of the Various Flow Regimes in a Spherical Annulus

The spherical Couette system, consisting of the flow in the annular gap between two concentric rotating spheres, is a convenient problem for studying the laminar–turbulent transition. Many of the transitional phenomena encountered in this flow are of fundamental relevance for the understanding of global processes in the planetary atmospheres as well as in astrophysical and geophysical motions. Furthermore, the study of spherical Couette flow (SCF) is of basic importance in the field of hydrodynamic stability. This paper focuses principally on the numerical prediction of various transitions between flow regimes in a confined spherical gap between a rotating inner sphere and a fixed outer spherical shell. The finite-volume-based computational fluid dynamics, FLUENT software package, is adopted to investigate numerically the flow of a viscous incompressible fluid in the closed spherical gap. Two important dimensionless parameters completely define the flow regimes: the Reynolds number, Re = Ω1R12/ν, for the rotation of the inner sphere and the gap width, β = (R2 − R1)/R1 = 0.1, for the geometry. The numerical calculations are carried out over a range of Reynolds number from two until 60,000. The numerical results are compared with the experimental data available in the literature, and the agreement between the two approaches is very good. The laminar–turbulent transition, the onset of different instabilities, the formation mechanisms of various structures, and the flow behavior are examined and described in detail by the pressure field, meridional streamlines, circumferential velocity, and skin friction coefficient. In addition, the velocity time series and the corresponding power spectral density are considered and analyzed over a large range of Reynolds number. Three kinds of fundamental frequencies expressed by F0, F1, and F2 are obtained corresponding to the spiral mode associated with the wavy mode (SM + WM), the wavy mode (WVF), and the chaotic fluctuation (CF), respectively. However, no sharp fundamental frequency components are observed for the turbulent regime.

Stability of two-layer fluid flow

The problem of two-layer convective flow of viscous incompressible fluids in a horizontal channel with solid walls in the presence of evaporation is considered in the Oberbeck–Boussinesq approximation assuming that the interface is an undeformable thermocapillary surface and taking into account the Dufour effect in the upper layer which is a mixture of gas and liquid vapor. The effects of longitudinal temperature gradients at the boundaries of the channel and the thicknesses of the layer on the flow pattern and the evaporation rate are studied under conditions of specified gas flow and the absence of vapor flow on the upper boundary of the channel. It is shown that the long-wavelength asymptotics for the decrement is determined from the flow characteristics, the longwavelength perturbations occurring in the system decay monotonically, and the thermal instability mechanism is not potentially the most dangerous.

Unsteady self-similar viscous flow near a stagnation point

The problem of unsteady viscous incompressible fluid flow near a stagnation point is considered. Self-similar solutions describing plane and axisymmetric flows are constructed.

Unsteady flow of shear-thinning non-Newtonian incompressible fluid through a twin-screw extruder

The unsteady flow of viscous incompressible shear-thinning non-Newtonian fluid with mixed boundary is investigated. The boundary condition on the outflow is the modified natural boundary condition, it contains the additional nonlinear term, which enables us to control the kinetic energy of the backward flow. The global existence of weak solution is proved. The fictitious domain method which consists in filling the moving rigid screws with the surrounding fluid and taking into account the boundary conditions on these bodies by introducing a well-chosen distribution of boundary forces is used.

CFD 2D Description of Local Flow of Polymer Workpiece through a modified U-Shaped Die During Equal Channel Multiple Angular Extrusion

The present article is focused on a 2D computational fluid mechanics study of local viscous flow dynamics and the formation character of rotary modes of deformation during Equal Channel Multiple Angular Extrusion (ECMAE) of a polymer workpiece fluid model through a U-shaped die with parallel slants in channel intersection zones. The present local flow problem was experimentally analyzed using physical simulation methods and theoretically studied with numerical fluid mechanics techniques. The computational approach has been grounded on the numerical finite difference solution of the boundary value problem for the Navier-Stokes equations in the curl transfer form for the local viscous flow of incompressible Newtonian fluid through a U-shaped rectangular die with parallel slants. The derived research results allow us to draw a conclusion that the implementation of a geometric design of parallel slants within a 2-turn U-shaped die results in localization of the maximum tangential stresses within the workpiece volume to the vicinity of these parallel slants during ECMAE.

К расчету машущего гибкого профиля в потоке вязкой несжимаемой жидкости

К расчету машущего гибкого профиля в потоке вязкой несжимаемой жидкости

Unsteady hydromagnetic chemically reacting mixed convection flow over a permeable stretching surface with slip and thermal radiation

The present investigation deals with unsteady hydromagnetic chemically reacting mixed convection flow of incompressible viscous fluid past a vertically moving permeable stretching sheet in the presence of suction/injection, heat source/absorption, thermal radiation, viscous dissipation and slip effects. The governing partial differential equations are reduced into a set of non-linear ordinary differential equations by suitable transformations. Keller box method is applied to solve the system of non-linear ordinary differential equations for which the implementation is made with the help of matlab. The important parameters in this study are: Prandtl number Pr, Schmidt number Sc, buoyancy force parameter λ, radiation parameter Nr, magnetic parameter M, buoyancy forces ratio parameter N, the unsteady parameter A, suction/injection parameter s, Eckert number Ec, heat source/sink parameter Q, chemical reaction parameter R, velocity slip parameter sv, temperature slip parameter st and species concentration slip parameter sm. Effects of these parameters on velocity, temperature and species concentration profile of the fluid are presented and analyzed graphically. Furthermore, numerical investigations have been made for the skin friction coefficient and surface heat and mass transfer rates for some of the parameters.

An Efficient Implicit Compact Streamfunction Velocity Formulation of Two Dimensional Flows

In this paper, we develop a class of implicit, unconditionally stable compact schemes for solving coupled fourth order and second order semilinear streamfunction and temperature equations respectively representing unsteady Navier---Stokes (N---S) equations for incompressible viscous fluid flows. The governing equations are presented in a generic form from which specific equations are obtained for several two dimensional (2D) incompressible viscous fluid flow problems. The streamfunction and the temperature equations are all solved iteratively in a coupled system of equations for the four field variables consisting of streamfunction, two velocities and temperature. The discretized form of biharmonic equation in streamfunction consists on 5-point stencil of streamfunction and is found to be second-order accurate both for spatially and temporally. In addition, we have considered two strategies for the discretization of the energy equation, which are second order accurate 5-point and fourth order accurate 9-point compact scheme. The formulation is made efficient by decreasing the computational complexity and is used to solve several 2D time dependent well studied benchmark problems. It is seen to efficiently capture both time wise and steady-state solutions of the N---S equations with Dirichlet as well as Neumann boundary conditions. The results obtained using our proposed scheme are in excellent agreement with the results available in the literature and they clearly establish the efficiency and the accuracy of the proposed scheme.

Combined effect of variable viscosity and thermal conductivity on free convection flow of a viscous fluid in a vertical channel

Purpose – The purpose of this paper is to investigate the effect of exponential viscosity-temperature relation, exponential thermal conductivity-temperature relation and the combined effects of variable viscosity and variable thermal conductivity on steady free convection flow of viscous incompressible fluid in a vertical channel. Design/methodology/approach – The governing equations are solved analytically using regular perturbation method. The analytical solutions are valid for small variations of buoyancy parameter and the solutions are found up to first order for variable viscosity. Since the analytical solutions have a restriction on the values of perturbation parameter and also on the higher order solutions, the authors resort to numerical method which is Runge-Kutta fourth order method. Findings – The skin friction coefficient and the Nusselt number at both the plates are derived, discussed and their numerical values for various values of physical parameters are presented in tables. It is found that an increase in the variable viscosity enhances the flow and heat transfer, whereas an increase in the variable thermal conductivity suppresses the flow and heat transfer for variable viscosity, variable thermal conductivity and their combined effect. Originality/value – This research is relatively original as, to the best of the authors’ knowledge, not much work is done on the considered problem with variable properties.

Similarity Solutions of Unsteady Mixed Convective Boundary Layer Flow of Viscous Incompressible Fluid along Isothermal Horizontal Plate

Unsteady mixed convective boundary layer flow of viscous incompressible fluid along isothermal horizontal plate is analyzed through Similarity Solutions. The governing partial differential equations are transformed into ordinary differential equations using the similarity transformation and solved numerically along with shooting technique. The flow field for the fluid velocity, temperature and concentration at the plate surface are significantly influenced by the governing parameters such as unsteadiness parameter, permeability parameter, Prandtl number, Schmidt number and the other driving parameters. The results show that both fluid velocity and temperature decrease but no significant effect on concentration for the increasing values of Prandtl number. It is also exposed that velocity and concentration is higher at lower Schmidt number for low Prandtl fluid. Finally, the dependency of the Skin-friction co-efficient, Nusselt number and Sherwood number, which are of physical interest, are also illustrated in tabular form for the governing parameters.

Stability of Large Vortex―Two-Dimensional Flows of Incompressible Viscous Fluid at Large Reynolds Numbers

Stability of Large Vortex―Two-Dimensional Flows of Incompressible Viscous Fluid at Large Reynolds Numbers

Свободное программное обеспечение для моделирования жидкости со свободной поверхностью

Problems of free-surface flow of viscous incompressible fluid are very useful in different practical cases. There are many specifies and limitations in these problems which are critically important for correct solving. The main goal is the review of existing numerical methods which can apply for modeling of free-surface flows and open-source programs where these methods are realized. Three methods for solving problems of free-surface flow were considered: Volume of Fluid, Smoothed Particle Hydrodynamics, Particle Finite Element Method v.2. They are realized in five open-source packages: OpenFOAM, Gerris, pySPH, DualSPHysics, Kratos. These packages were compared by modeling of two chosen cases: breaking of a dam and droplet impact to the liquid layer. Results of computations were compared with experimental results. There are good coincidence between them. The best results were obtained in OpenFOAM and Gerris. All main tools for modeling of free-surface flow are realized in these packages - the possibility of computations in 2D, 3D and axisymmetric model setup and also correct modeling of surface tension. Gerris can significantly accelerate computations in "big cases" due to dynamically adaptive remeshing. Further, DualSPHysics is the package for modeling of problems of coastal infrastructure where the most number of cases is 3D and the surface tension effect is negligible. The package pySPH was designed for clear demonstration of SPH working. The pySPH source code is on the Python language and not optimized. Kratos is the new package, which is in development now, therefore some tools are not developed in this moment.

Heat and Mass Transfer in Three Dimensional Free Convective Oscillatory Flow in Porous Medium with Constant Heat and Mass Flux in Presence Radiation for an optically Thin Fluid

A theoretical analysis of free convective flow of viscous incompressible fluid through a porous medium bounded by a flat porous plate subject to periodic suction and constant heat and mass flux has been presented. The flow becomes three dimensional due to variation of suction velocity in transverse direction. Analytical expression for velocity, temperature, concentration and skin friction are obtained using perturbation technique. Numerical solutions are obtained for different values Grash of number (G r ), mass Grashof number(Gc), Prandtl number (Pr), Schmidt number (Sc) and Radiation (R). It is found that non-dimensional velocity increases with increase of Gr, Gc and Sc and decreases with increase of R, non-dimensional temperature decreases with increasing of R, Concentration decreases with increase of Sc. and skin friction co-efficient increases with increase of Gr and R but effect of Gr is more than R.

Numerical simulation of the flow in the rotation cavities of turbopump assembly

The flow of viscous incompressible fluid in the lateral rotation cavity of centrifugal pump is considered. The finite-difference equations have been developed for numerical simulation of the flow in view of shear stresses in a spatial boundary layer that allow a disk resistance moment to be defined. The numerical results are presented.

Effects of Thermophoresis, Dufour, Hall and Radiation on an Unsteady MHD Flow past an Inclined Plate with Viscous Dissipation, Chemical Reaction and Heat Absorption and Generation

This paper investigates study of MHD(Magnetohydrodynamics) flow of viscous incompressible fluid past an inclined porous plate embedded in porous medium with the effects of Thermophoresis, Dufour, Hall, radiation, viscous dissipation, chemical reaction and heat generation or absorption. Non dimensional partial differential equations of governing equations of flow are solved numerically by applying Crank-Nicolson finite difference method for different values of parameters. Velocity, temperature, concentration profiles are discussed through graphs for different values of parameters and skin friction coefficients, Nusselt number and Sherwood number are discussed through tables.

3D simulation and analytical model of chemical heating during silicon wet etching in microchannels

We investigate chemical heating of a Silicon-on-Glass (SOG) chip during a highly exothermic reaction of silicon etching in potassium hydroxide (KOH) solution in a microchannel of 100-micron width inside a 1x1 cm SOG chip. Two modeling approaches have been developed, implemented and compared. (1) A detailed 3D model is based on unsteady Navier-Stokes equations, heat and mass transfer equations of a laminar flow of viscous incompressible fluid in microchannel, coupled to the heat transfer equation in the solid chip. 3D simulation results predicted temperature distributions for different KOH flow rates and silicon etching areas. Microchannels of a small diameter do not heat the chip due to the insufficient chemical heating of the cold fluid, whereas large-area etching (large channel diameter and/or length) leads to local overheating that may have negative effects on the device performance and durability. (2) A simplified analytical model solves a thermal balance equation describing the heating by chemical reactions inside the microchannel and energy loss by free convection of air around the chip. Analytical results compare well with the 3D simulations of a single straight microchannel, therefore the analytical model is suitable for quick estimation of process parameters. For complex microstructures, this simplified approach may be used as the first approximation.

Numerical solution of fluid-structure interaction represented by human vocal folds in airflow

The paper deals with the human vocal folds vibration excited by the fluid flow. The vocal fold is modelled as an elastic body assuming small displacements and therefore linear elasticity theory is used. The viscous incompressible fluid flow is considered. For purpose of numerical solution the arbitrary Lagrangian-Euler method (ALE) is used. The whole problem is solved by the finite element method (FEM) based solver. Results of numerical experiments with different boundary conditions are presented.

Joule Heating and Viscous Dissipation on Effects on MHD Flow over a Stretching Porous Sheet Subjected to Power Law Heat Flux in Presence of Heat Source

In the present work we investigate the effects of Joule heating and viscous dissipation on MHD fluid flow. The viscous incompressible fluid flows over a stretching porous horizontal sheet subjected to power law heat flux in presence of heat source. The equations of momentum and heat transfer governing the problem are transformed into a system of dimensionless differential equations, which in turn solved numerically using shooting technique. The effects of the Joule heating parameter, permeability parameter, heat source parameter, Eckert number and Prandtl number are discussed and tabulated.