CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   Main CFD Forum (http://www.cfd-online.com/Forums/main/)
-   -   The two drag contributions (http://www.cfd-online.com/Forums/main/3392-two-drag-contributions.html)

Hakeem April 28, 2001 13:33

The two drag contributions
 
Hi everybody ...

As most of you are aware, for creeping (slow) flow of Newtonian fluid moving over a sphere the ratio of pressure coefficient to viscous coefficient should be ~ 0.5. Unfortunately, when I use Fluent 5.3, it is not the case. The total coefficient is right, namely, for Re = 0.01, the total drag coefficient should be ~ 2400. I got it 2400.8. However the ratio of pressure coefficient to viscous coefficient is 640.66629/1760.1434 = 0.36. Could anyone think of possible reason.

John C. Chien April 28, 2001 15:08

Re: The two drag contributions
 
(1). Ask the code vendor whether what you are getting is consistent with the code you are using. (2). If they think, you are wrong, then ask them to show you how to get the right answer using the code. (3). We are not here to speculate reasons why you think you are not getting the right answer. (that is, a right answer from the code by you could be the wrong answer to the problem.) (4). There are endless reasons which could lead to such solution, mesh size, mesh distribution, not enough mesh points(cells), accuracy of numerical algorithm, convergence, location of boundary conditions, treatment of boundary conditions, etc... (5). Even the post-processing (graphic and derived variables) can give you headache from time to time.


All times are GMT -4. The time now is 23:49.