CFD Online Discussion Forums

CFD Online Discussion Forums (
-   CFX (
-   -   adding source term confusion (

tedmcc August 9, 2001 02:09

adding source term confusion

I am confused about adding the source term in the command file.

I set up a 3D problem of 2 phase flow (air and water). I want to inject, through a source term, a cold stream consisting of both phases into a geometry containing hot fluid.

If known

- the flow rate/ volume composition for each phase

- the velocity and

- inlet temperature,

1. does the size of the USER3D patch defined matter the relationship between flow rate and velocity? I mean the velocity was calculated based on the flow rate and the area of original inlet device present in the real system.

2. I am very confused about which type of sources to specify. Is it "TOTAL", "TOTAL FOR PHASE" or ???

Please help! Thanks.

Sascha August 10, 2001 06:57

Re: adding source term confusion
1. Forget the usage of USER3D patches, We have made very bad experiences using them via IPALL. 2. The sources shall be defined via USRSRC total for each phase... But when you add mass take care that you have to add source terms for several equations...

tedmcc August 11, 2001 03:47

Re: adding source term confusion
Hi Sascha

1 . could you elaborate a bit more on the bad experience on USER3D-patch and IPALL?

2 . When adding sources through USRSRC, does that mean there's no need to set user3d patch but set an IP location where the source term is, right?

Thank you for your help.

Sascha August 13, 2001 08:52

Re: adding source term confusion
1. The USER-3D patch has never worked properly in my tests. Mostly I had needed to set two different patches at the same location (porous and USER-3D). And it had been a very big problem to access the IP of the USER-3D. So I recommend to use geometry function or pointer functions set in a User-Scalar.

2. Really the best is to use IP locations or any pointer function first set by USRINT and all teh time used within the program. So you can be sure to set the coprrect source term...

raymond September 27, 2001 05:05

Re: adding source term confusion
For the USER3D, I have applied it for a long time. It can work well with simple source term, such as constant heat source. For complex source term, the best way is using USESCR subroutine. It's more flexible than USER3D. I nerver meet the problem of IP with CFX4.2, but the IP must be applied carefully on the complex geometry.

All times are GMT -4. The time now is 14:09.