Numerical solutions of the Navier-Stokes equations for the flow in a channel with a step


Book Description

The steady flow of a viscous fluid in a channel with a forward facing or a backward facing step is studied numerically. It is assumed that the channel is bounded by rigid walls, and the flow in the channel far from the step is the Poiseuille flow. It is shown that the length of a standing vortex behind a backward facing step increases roughly proportionally to the Reynolds number (R







Numerical Solutions of the Incompressible Navier-Stokes Equations in Two and Three-Dimensional Coordinates


Book Description

One of the most important applications of finite difference lies in the field of computational fluid dynamics (CFD). In particular, the solution to the Navier-Stokes equation grants us insight into the behavior of many physical systems. The 2-D and 3-D incompressible Navier-Stokes equation has been studied extensively due to its analogous nature to many practical applications, and several numerical schemes have been developed to provide solutions dedicated to different environmental conditions (such as different Reynolds numbers). This research also covers the assignment of boundary conditions, starting with the simple case of driven cavity flow problem. In addition, several parts of the equations are given implicitly, which requires efficient ways of solving large systems of equations.We also considered numerical solution methods for the incompressible Navier-Stokes equations discretized on staggered grids in general coordinates. Numerical experiments are carried out on a vector computer. Robustness and efficiency of these methods are studied. It appears that good methods result from suitable combinations of multigrid methods.Numerically solving the incompressible Navier-Stokes equations is known to be time-consuming and expensive; hence this research presents some MATLAB codes for obtaining numerical solution of the Navier-Stokes equations for incompressible flow through flow cavities, using method of lines, in three-dimensional space (3-D). The code treats the laminar flow over a two-dimensional backward-facing step, and the results of the computations over the backward-facing step are in excellent agreement with experimental results.




Numerical Simulation of Fluid Flow and Heat/Mass Transfer Processes


Book Description

Computational fluid flow is not an easy subject. Not only is the mathematical representation of physico-chemical hydrodynamics complex, but the accurate numerical solution of the resulting equations has challenged many numerate scientists and engineers over the past two decades. The modelling of physical phenomena and testing of new numerical schemes has been aided in the last 10 years or so by a number of basic fluid flow programs (MAC, TEACH, 2-E-FIX, GENMIX, etc). However, in 1981 a program (perhaps more precisely, a software product) called PHOENICS was released that was then (and still remains) arguably, the most powerful computational tool in the whole area of endeavour surrounding fluid dynamics. The aim of PHOENICS is to provide a framework for the modelling of complex processes involving fluid flow, heat transfer and chemical reactions. PHOENICS has now been is use for four years by a wide range of users across the world. It was thus perceived as useful to provide a forum for PHOENICS users to share their experiences in trying to address a wide range of problems. So it was that the First International PHOENICS Users Conference was conceived and planned for September 1985. The location, at the Dartford Campus of Thames Polytechnic, in the event, proved to be an ideal site, encouraging substantial interaction between the participants.




Numerical Solutions of the Navier-Stokes Equations for the Supersonic Laminar Flow Over a Two-dimensional Compression Corner


Book Description

Numerical solutions have been obtained for the supersonic, laminar flow over a two-dimensional compression corner. These solutions were obtained as steady-state solutions to the unsteady Navier-Stokes equations using the finite-difference method of Brailovskaya, which has the second-order accuracy in the spatial coordinates. Good agreement was obtained between the computed results and the wall pressure distributions measured experimentally by Lewis, Kubota, and Lees for Mach numbers of 4 and 6.06, and respective Reynolds numbers, based on free-stream conditions and the distance from the leading edge to the corner, of 6.8 x 104 and 1.5 x 105. In those calculations, as well as in others, sufficient resolution was obtained to show the streamline pattern in the separation bubble. Upstream boundary conditions to the compression-corner flow were provided by numerically solving the unsteady Navier-Stokes equations for the flat-plate flow field, beginning at the leading edge. The compression-corner flow field was enclosed by a computational boundary with the unknown boundary conditions supplied by extrapolation from internally computed points. Numerical tests were performed to deduce that the magnitude of the errors introduced by the extrapolation was small. Calculations were made to show the effect of ramp angle and wall suction on the interaction flow field. The pressure distributions obtained in the present calculations, including a case of incipient separation, were plotted together by using the free-interaction scaling of Stewartson and Williams. A good correlation of the numerical results was found, but only fair agreement was found between this correlation and the universal pressure distribution found numerically by Stewartson and Williams.