CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   CFX (http://www.cfd-online.com/Forums/cfx/)
-   -   Negative pressure in 2D problem (http://www.cfd-online.com/Forums/cfx/25233-negative-pressure-2d-problem.html)

 Micgre February 14, 2008 04:58

Negative pressure in 2D problem

Hello world,

I tried to study the pression lost in a valve. To simplify, I tried to work in a 2D problem. You can see my model here :

http://img101.imageshack.us/img101/1...opimagemi4.png

My parameters are : - Air at 25°C - Steady state - Inlet = Pressure at 2200Pa - Outlet = Mass air flow at 0.0009 kg/s - Symetry on both side

In the result, pressure on outlet is around -100000Pa !!!

When I tryed on an 3D model, with same parameters, the result are Ok.

Do you have any idea of this problem on 2D ?

Thanks a lot for your help

Micgre

 Glenn Horrocks February 14, 2008 17:45

Re: Negative pressure in 2D problem

Hi,

Did you scale the mass flow rate to reflect the smaller area of the 2D model? For example, if you are modelling a channel 1 metre wide using a 2D flow with a 1mm wide slice, you will need to reduce the mass flow rates by a factor of 1000.

Glenn Horrocks

 Micgre February 18, 2008 03:24

Re: Negative pressure in 2D problem

I already done this ratio :( I don't understand why this flow rate delta can create negative pressure ?