Showing papers by "Suhas V. Patankar published in 1989"

Numerical Prediction of Heat Transfer and Fluid Flow in Rectangular Offset-Fin Arrays

Abstract: A computational study of laminar flow and heat transfer in the channels of a rectangular offset-fin heat exchanger is presented. Computations are carried out for the entrance region and continued till the flow becomes periodically fully developed due to the repetitive nature of the geometry. All the heat transfer surfaces are assumed to be at a uniform temperature. A parametric study is made for various values of the aspect ratio and the fin-length parameter. Results show that developing length is about 5-10 modules. Local results are presented to provide a good physical understanding of the flow and heat transfer phenomena. A comparison of the numerical results with the available experimental data is also presented.

Robust semidirect finite difference methods for solving the Navier–Stokes and energy equations

Abstract: Semidirect solution techniques can be an effective alternative to the more conventional iterative approaches used in many finite difference methods. This paper summarises several semidirect techniques which generally have not been applied to the Navier-Stokes and energy equations in finite difference form. The methods presented use both successive substitution and Jacobian-based updates as well as two variations of Broyden's full matrix update. A hybrid method is also presented, as is a norm-reducing search technique that can be used to enhance the convergence characteristic of any semidirect approach. See also the following Abstract.

A block-corrected subdomain solution procedure for recirculating flow calculations

Abstract: This paper describes a robust and efficient subdomain solution procedure for two-dimensional recirculating flows. The solution domain is divided into a number of overlapping subdomains, and a direct fully coupled solution is obtained for each subdomain using a sparse matrix form of LU decomposition. An effective parabolic block correction procedure, which calculates global corrections to the tentative solution by a marching technique similar to that used for boundary layer flows, is used to accelerate the convergence of the basic procedure. The use of effective block correction is found to be essential for the success of the subdomain approach on strongly recirculating flows. In a number of laminar two-dimensional flows, the new block-corrected method performed extremely well, rivaling the best direct methods in execution time, while requiring substantially less computer storage. The new method proved to be from two to ten times faster than conventional iterative methods, while requiring only a moderate increase in storage.

Equations for solving the navier-stokes and energy

Abstract: SUMMARY Semidirect solution techniques can be an effective alternative to the more conventional iterative approaches used in many finite difference methods. This paper summarizes several semidirect techniques which generally have not been applied to the Navier-Stokes and energy equations in finite difference form. The methods presented use both successive substitution and Jacobian-based updates as well as two variations of Broyden's full matrix update. A hybrid method is also presented, as is a norm-reducing search technique that can be used to enhance the convergence characteristics of Any semidirect approach. These methods have been compared with the well known iterative methods SIMPLE and SIMPLER. The comparison was performed on the natural convection and driven cavity problems. The semidirect methods proved to be reliably convergent without the need for a priori specification of variable under-relaxation factors, which was necessary with the iterative methods. Natural convection and driven cavity solutions have been readily obtained with the proposed methods for Rayleigh and Reynolds numbers up to 10" and 10' respectively. Of the semidirect techniques, the hybrid approach was the most robust. From an arbitrary zero initial guess this method was able to obtain a solution to the natural convection problem for Rayleigh numbers three orders of magnitude larger than was possible with the Newton--Raphson update. The computational effort required by the semidirect methods is comparable to that required by the iterative methods; however, the memory requirements can be significantly greater.