# Negative pressure in 2D problem

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 February 14, 2008, 04:58 Negative pressure in 2D problem #1 Micgre Guest   Posts: n/a Sponsored Links 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

 February 14, 2008, 17:45 Re: Negative pressure in 2D problem #2 Glenn Horrocks Guest   Posts: n/a 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

 February 18, 2008, 03:24 Re: Negative pressure in 2D problem #3 Micgre Guest   Posts: n/a I already done this ratio I don't understand why this flow rate delta can create negative pressure ? Thanks for your help.

 February 21, 2008, 11:45 Re: Negative pressure in 2D problem #4 Micgre Guest   Posts: n/a I think my problem is from symetry because when I work with my 3D model and cut an half, I've got negative pressure... But I don't understand why...

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