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 sometimes1900 November 4, 2008 06:33

different pressures in CFX-Post

Hi CFX user, in the compressible flow simulation there are three pressures in the CFX-Post, Absolute Pressure, Pressure and Total pressure. Can anyone tell me what the diffence is? Which pressure is used as the static pressure? thanx in advance Regards

 John S. November 4, 2008 10:51

Re: different pressures in CFX-Post

Pressure = Static Pressure - Reference Pressure Absolute Pressure = Static Pressure + Reference Pressure

 CycLone November 4, 2008 11:39

Re: different pressures in CFX-Post

Total Pressure = Static Pressure + Dynamic Pressure

I.e. it is the Stagnation Pressure

 Pascal November 5, 2008 06:02

Re: different pressures in CFX-Post

Are you sure Cyclone that in CFX-Post Total Pressure= static pressure + dynamic pressure? Isn't it Total Pressure=static pressure+dynamic pressure-Pref?

(I know that your definition is the right one, but I think that CFX-post is internaly changing the definition, 'cause if you plot pressure and total pressure over a wall surface you find the same...)

Let me know if you think I'm wrong, because it's something that I have only noticed by myself...

 CycLone November 6, 2008 12:30

Re: different pressures in CFX-Post

Sorry, you're right. It is reported relative to the domain reference pressure.

At a wall, the velocity is zero, so the dynamic pressure is zero and thus the total pressure is equal to the static pressure.

-CycLone

 powpow February 5, 2013 12:10

Hi!
In CFD-Post I can only choose between "pressure" and "total pressure" to be shown on my plane.
I need the "static pressure", so I have to choose "pressure"?

Am I right?

 ghorrocks February 5, 2013 18:13

Pressure is the static pressure. Note it has the hydrostatic component removed, if that is relevant. See the documentation for more information.

 gemxx July 12, 2015 09:14

Is it possible to draw dynamic pressure directly in Ansys CFX ?
Because I can draw the figures whic can show the distrubition of the static pressure and total pressure, but I wanna see the distrubition of the dynamic pressure.

If you can explain how it can be possible, I would be very gratefull.

 ghorrocks July 12, 2015 18:47

Define a variable with an expression Total Pressure - Pressure. Then it is a variable you can do anything you like with.

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