CFD Online Discussion Forums (https://www.cfd-online.com/Forums/)
-   Main CFD Forum (https://www.cfd-online.com/Forums/main/)
-   -   Artificial Dissipation (https://www.cfd-online.com/Forums/main/8977-artificial-dissipation.html)

 Fereidoun-e-Jam April 6, 2005 07:43

Artificial Dissipation

Dear Friends,

I am trying to simulate the flow field over a 2d bump, i.e. 2d Euler equations. I have a question that how should I calculate the artificial dissipation terms on the first two rows of the cells near the wall (especially the first row over the wall). I need the value of the pressure on the wall for boundary condition, is it possible to extrapolate the unknown wall pressure from inside the field?

Your attention and help will be highly appreciated,

With the best regards,

F. Jam

 Mani April 7, 2005 14:51

Re: Artificial Dissipation

How do you implement boundary conditions (ghost cell?)

About the pressure: Yes, you can use extrapolation from the interior. In the simplest case you can assume the normal pressure derivative to be zero (pressure on the wall is the same as in the first cell). More accurately, you can apply the normal momentum equation to get the pressure (search for the reference by A. Rizzi).

 Fereidoun April 9, 2005 10:48

Re: Artificial Dissipation

Dear Sir,

Thanks for your comments. I wrote my code. But it does not work because in about 50 first iterations it diverges. I applied two ghost cells below the lower wall and two above the upper wall, also two before the inlet and two after outlet for calculating artificial dissipation terms. But for pressure on the wall I used extrapolation. My inlet boundary condition is supersonic. And outlet also is supersonic. So for inlet I set free stream values for my conservative variables and for the outlet I used extrapolation from the field. I do no know where is my mistake I checked my code many times but it does not converges at all. If you have a FVM code in FORTRAN for this problem (flow in a channel over a circular bump) would you send it for me please?

With the best regards,

F. Jam,

 Mani April 10, 2005 22:16

Re: Artificial Dissipation

which scheme do you use? JST?

 All times are GMT -4. The time now is 22:33.