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lost_soul May 10, 2000 04:42

programming glitch or concept error???
hi ppl.. i have trying to test my staggered grid code written in primitive variables over a simple problem which a rectangular box with an inflow on one side and the outflow on the other end.. however while solving the pressure poissons equation using the iterative method the solution doesnt coverge after some values.. its just stays the same. i have been following the algorithm as give in "introduction to theoretical and computational fluid dynamnics" by c.pozridikis(pg 618-620)..i guess there is some problem in the pressure boundary condition as if i comment the pressure codeline for 1 of the corner nodes it converges and gives me results as if there were a sink at that corner node..but i have sincerely tried to follow the algo in pozrikidis as it does take into the account the "correct" boundary conditions demonstrated by gresho and sani(1987). what could possibly be wrong???any hints on the rite algo?? ready to discuss with anyone on 1-to-1 basis./. just mail me.. thanks for all.. :) urs lost again.. lost_soul

John C. Chien May 10, 2000 20:01

Re: programming glitch or concept error???
(1). Corners are always very difficult areas to handle correctly in the first place. (2). Try to avoid geometry with corners first, and check out your code with rounded corners (with sufficient nodes on the rounded corner). (3). The best way to learn is to follow someone's working code, instead of following someone's published paper. In most cases, it is hard to reproduce the published results using your re-created code. (4). So, learn from the source code of a working code. Even with this method, from time to time, you will discover old bugs in a working code.

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