Improved solution of steady,viscous, incompressible flow between two rotating spheres

A refined solution is presented for the analysis of viscous, incompressible, steady flow between two rotating spheres. A new method, used previously for simpler problems only, is adapted to this problem. The method allows the use of small grid spacing and thus yields improved accuracy.     

Numerical studies of steady,viscous, incompressible flow between two rotating spheres

A new numerical method, developed for the study of secondary flow in a curved tube, is adapted and extended to the study of viscous, incompressible, steady flow between two rotating spheres. The Navier-Stokes equations are approximated by a triple sequence of linear problems, each of which has a diagonally dominant coefficient matrix. Computer examples are described and discussed.     

Influence of viscous dissipation in a fluid between concentric rotating spheres

The steady motion of a viscous fluid contained between two concentric spheres which rotate about a common axis with different angular velocities is considered. A second-order method which was introduced previously by the authors to obtain numerical solutions of a class of Navier-Stokes problems coupled with a superimposed thermal field is successfully extended here to investigate the influence of the internal generation of heat by viscous dissipation on the thermal field. The resulting thermal field solutions are presented for various values of the Eckert number and the rotation ratio. It is shown that the inclusion of heat generation by viscous dissipation significantly alters the thermal field behavior, while the relative rates of rotation of the two spheres do not change the general character of the thermal field.     

Finite difference solution to the flow between two rotating spheres

This paper describes a numerical method for calculating incompressible viscous flows between two concentric rotating spheres. The dependent variables describing the axisymmetric flow field are the azimuthal components of the vorticity, of the velocity vector potential and of the velocity. The coupled set of governing partial differential equations is written as a system of strictly second-order equations by introducing vorticity conditions of an integral character in a meridional plane. Such conditions generalize the one-dimensional integral conditions employed by Dennis and Singh to calculate steady-state solutions of the same problem using Gegenbauer polynomials and finite differences. The basic equations are discretized in space and in time by means of the finite-difference method. A fourth-order accurate centred-difference approximation of the advection terms is employed and a nonlinearly implicit scheme for the discrete time integration is here considered. A general finite-difference algorithm for steady-state and time-dependent problems is obtained which has no relaxation parameter and makes extensive use of fast elliptic solvers. The numerical results obtained by the present method are found to be in good agreement with the literature and confirm the nonuniqueness of the steady-state solution in a narrow spherical gap at certain regimes.     

Finite element analysis of viscous,incompressible fluid flow: Part 2: Applications

The first part of this paper described a general numerical procedure for the analysis of two-dimensional flows of viscous, incompressible fluids, using the finite element method. A number of special computational procedures were also discussed that allowed significant reductions to be made in the computational effort required in the solution of problems. The present paper is devoted to demonstrating the utility of the methods described by the solution of several example problems. The illustrative examples consist of flow in a plane 90° T, flow in a cavity and flow around a circular cylinder.     

Finite element analysis of viscous,incompressible fluid flow: Part 1 : Basic methodology

A numerical procedure is developed for the analysis of general two-dimensional flows of viscous, incompressible fluids using the finite element method. The partial differential equations describing the continuum motion of the fluid are discretized by using an integral energy balance approach in conjunction with the finite element approximation. The nonlinear algebraic equations resulting from the discretization process are solved using a Picard iteration technique.A number of computational procedures are developed that allow significant reductions to be made in the computational effort required for the analysis of many flow problems. These techniques include a coarse-to-fine-mesh rezone procedure for the detailed study of regions of particular interest in a flow field and a special finite element to model far-field regions in external flow problems.     

Finite element analysis of viscous fluid flow

A finite element model for the analysis of two dimensional viscous flows is formulated using the virtual work method. The model is in part based on a finite element shell model, using the same reduced integration of quadratic interpolations for all variables[1]. Differences from preceding formulations are that integration by parts is applied to the continuity equation, yielding different loading terms which are more easily defined in some problems, and a new approach is used for the convective inertia terms, giving a clearer interpretation of their effects which are distributed to both sides of the nonlinear recurrence relation. In the case of compressible flow, for which comparatively few formulations have been proposed to date, the thermal energy equation is used to form a two stage solution and here this seems the most natural and economical approach.     

Theory and implementation of a semi-implicit finite element method for viscous incompressible flow

A numerical procedure for solving the time-dependent, incompressible Navier-Stokes equations is derived based on the operator-splitting technique. This operator split allows separate operations on each of the variable fields to enable pressure-velocity coupling. Discretizations of the equations are formed on a nonstaggered finite element mesh and the solutions are obtained in a time-marching fashion. Several benchmark problems, including a standing vortex problem, a lid-driven cavity and a flow around a rectangular cylinder, are studied to demonstrate the robustness and accuracy of the present algorithm.     

Error control and mesh optimization for high-order finite element approximation of incompressible viscous flow

We discuss the use of a posteriori error estimates for high-order finite element methods during simulation of the flow of incompressible viscous fluids. The correlation between the error estimator and actual error is used as a criterion for the error analysis efficiency. We show how to use the error estimator for mesh optimization which improves computational efficiency for both steady-state and unsteady flows. The method is applied to two-dimensional problems with known analytical solutions (Jeffrey-Hamel flow) and more complex flows around a body, both in a channel and in an open domain.     

Two-dimensional nonsteady viscous flow simulation on the Navier-Stokes Computer miniNode

The needs of large-scale scientific computation are outpacing the growth in performance of mainframe supercomputers. In particular, problems in fluid mechanics involving complex flow simulations require far more speed and capacity than that provided by current and proposed Class VI supercomputers. To address this concern, the Navier-Stokes Computer (NSC) was developed. The NSC is a parallel-processing machine, comprised of individual Nodes, each comparable in performance to current supercomputers. The global architecture is that of a hypercube, and a 128-Node NSC has been designed. New architectural features, such as a reconfigurable many-function ALU pipeline and a multifunction memory-ALU switch, have provided the capability to efficiently implement a wide range of algorithms. Efficient algorithms typically involve numerically intensive tasks, which often include conditional operations. These operations may be efficiently implemented on the NSC without, in general, sacrificing vector-processing speed. To illustrate the architecture, programming, and several of the capabilities of the NSC, the simulation of two-dimensional, nonsteady viscous flows on a prototype Node, called the miniNode, is presented.     

Finite difference methods for viscous incompressible global stability analysis

In the present article some high-order finite-difference schemes and in particularly dispersion-relation-preserving (DRP) family schemes, initially developed by Tam and Webb [Dispersion-relation-preserving finite difference schemes for computational acoustics, J. Comput. Phys. 107 (1993) 262-281.] for computational aeroacoustic problems, are used for global stability issue. (The term global is not used in weakly-non-parallel framework but rather for fully non-parallel flows. Some authors like Theofilis [Advances in global linear instability analysis of non-parallel and three-dimensional flows, Progress in Aerospace Sciences 39 (2003) 249-315] refer to this approach as “BiGlobal”.) These DRP schemes are compared with different classical schemes as second and fourth-order finite-difference schemes, seven-order compact schemes and spectral collocation scheme which is usually employed in such stability problems. A detailed comparative study of these schemes for incompressible flows over two academic configurations (square lid-driven cavity and separated boundary layer at different Reynolds numbers) is presented, and we intend to show that these schemes are sufficiently accurate to perform global stability analyses.     

Pseudospectral multi-domain method for incompressible viscous flow computation

We present a multi-domain pseudospectral method for the calculation of incompressible viscous flow. Governing equations are written in primitive variables formulation. Velocity components and pressure are discretized on the same grid of collocation points. A coupling algorithm for the Stokes problem is investigated and preliminary results are presented in the two-dimensional case.     

Solution domain decomposition method for viscous incompressible flow

A solution domain decomposition method is developed for steady state solution of the biharmonic-based Navier-Stokes equations. It consists of a domain decomposition in conjunction with Chebyshev collocation for spatial discretization. The interactions between subdomains are effectively decoupled by means of a superposition of auxiliary solutions to yield a set of independent elementary problems which can be solved concurrently on multiprocessor computers. Assessments are carried out to a number of test problems including the two-dimensional steady flow in a driven square cavity. Illustrative examples indicate a good performance of the proposed methodology which does not affect the convergence and stability of the discretization scheme. Spectral accuracy is retained with absolute error decaying in an exponential fashion. The numerical solutions for the driven cavity compare favorably against previously published numerical results except for a slight overprediction in the vertical velocity component at Reynolds number of 400. TheC ³ continuity is speculated to be its cause.     

On the velocity-vorticity approach to viscous incompressible flow

Archives of Computational Methods in Engineering - This work present a selection of recent analytical and numerical results on the equations describing 2D and 3D laminar flows of a newtonian...     

Double-disk rotating viscous micro-pump with slip flow

In this paper numerical solution was provided for the 2D, axisymmetric Navier-Stokes equations coupled with energy equation for gaseous slip flow between two micro rotating disks pump. A first-order slip boundary condition was applied to all internal solid walls. The objective is to study the effect of Knudsen number, rotational Reynolds number and gap height on pump head, flow rate, coefficient of moments and overall micro-pump efficiency. Pump head, flow rate, coefficient of moments and pump efficiency were calculated for various pump operating conditions when the mass flow rate is applied at the pump inlet port. Detailed investigations were performed for rotational Reynolds number equals to 10. Effect of gap height between the two disks was studied. Effect of rotational Reynolds number on maximum flow rate and maximum pressure rise was simulated. The present numerical results for no-slip were compared with previously published experimental and theoretical data and found to be in a very good agreement. Knudsen number Kn values were found to be major parameters that affect the performance of pump. Pump performance decreases with increasing Kn. Optimal pump performance occurs around middle point of pump operating range. Pump operating range decreases with increasing Kn numbers. Pump performance is found to experience a steep degradation for Kn approaching 0.1. Maximum flow rate increases with rotational speed almost linearly. Maximum pressure rise also increases with rotational speed. Reducing gap height results in increasing maximum pressure rise, while increasing gap height results in larger maximum flow rate.     

On the flow between two rotating shrouded discs

Numerical solutions to the full Navier Stokes equations for the flow enclosed between two rotating discs and a sidewall are presented. The sidewall remains fixed throughout, while we consider examples in which: (i) the bottom disc is rotating and the top disc is fixed; (ii) the two discs rotate in the same sense; (iii) the two discs rotate in opposite senses. We present solutions up to a Reynolds number of 1200, using second order central finite differencing.     

An auxiliary potential velocity method for incompressible viscous flow

In this article a novel auxiliary potential velocity scheme for incompressible flows is presented. The present method is characterized by high accuracy, robustness and simple implementation. Its advantages are highlighted by applying it to several benchmark problems (internal duct flow, flow over a backward facing step) and by extensive comparison with other numerical methods such as SIMPLE and CVP concerning accuracy and convergence. The accuracy of the predictions of the present method is demonstrated through comparison with experimental data.     

Time-dependent solutions of the viscous incompressible flow past a circular cylinder by the method of series truncation

Semi-analytic solutions of the Navier-Stokes equations are calculated for two-dimensional, symmetrical, viscous incompressible flow past a circular cylinder. The stream and vorticity functions are expanded in the finite Fourier series and then substituted in the Navier-Stokes equations. This led to a system of coupled parabolic partial differential equations which are solved numerically. More terms of the series are required as Reynolds number increases and the present calculations were terminated at Reynolds number 600 with 60 terms of Fourier series. The results are compared with similar calculations and experimental data for Reynolds numbers 60, 100, 200, 500, 550 and 600. At the termination of the calculations for Reynolds numbers 60 and 100, the separation angle, the wake length, the drag coefficient, and the vorticity distributions around the surface were very close to their steady-state values. A secondary vortex appeared on the surface of the cylinder in the case of Reynolds numbers 500, 550 and 600. The wake length, the drag coefficient and the separation angle differ slightly at a given instant in the case of Reynolds numbers 500, 550 and 600.