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-   -   What pressure profile to provide to ABAQUS ??? (http://www.cfd-online.com/Forums/fluent/39378-what-pressure-profile-provide-abaqus.html)

thomas January 24, 2006 18:00

What pressure profile to provide to ABAQUS ???
 
Here is a quick question. I am having a high velcoity (60 m/s) flow impacting onto some blades. After convergence i am extracting the pressure values onto the blade to provide it to abaqus to check the stress contour. Which Pressure Profile Should I use ? The Static Pressure Profile or the TOTAL Pressure Profile - Static + Dynamic?.

In my head it is the Total Pressure profile to account the pressure due a fluid momentum but i am asking for a comfirmation here. THANKS in adavnce !!!

Thomas January 24, 2006 18:55

Re: What pressure profile to provide to ABAQUS ???
 
You should use the pressure that is seen by the blade. If the blade is not moving you should use the total pressure.

thomas

thomas January 24, 2006 19:23

Re: What pressure profile to provide to ABAQUS ???
 
Thanks effectively the blade is not moving, so i will use the total pressure ! THANKS MUCH !

Luca January 25, 2006 04:11

Re: What pressure profile to provide to ABAQUS ???
 
I'm sorry but to me you should use the static one. Luca

thomas January 25, 2006 09:46

Re: What pressure profile to provide to ABAQUS ???
 
OK, xould you explain to me why you think so ? .. also maybe theword blade is not the right term, i am not studying a pump or anything rotative just a high velocity flow around a wall. Thanks for your quick answer !


Luca January 25, 2006 09:53

Re: What pressure profile to provide to ABAQUS ???
 
Have you ever seen a Cp (pressure-coefficient) plot of an aerfoil? Remember how Cp is defined. Total pressure is just a definition. So sorry for my short answer... Luca

Razvan January 27, 2006 05:33

Re: What pressure profile to provide to ABAQUS ???
 
Dear fellow Fluent users, we are talking about hypersonic flows, multiphase, deforming meshes, extremely complicated heat transfer, but we seem to have forgotten even the basics of fluid mechanics!!!

Mr. Luca is wright, you should use static pressure! Why? The answer is simple: imagine only how these two pressures are measured (static and total).

- static pressure is measured using a gauge with a hole parallel to the main flow direction, so it measures actually the pressure that THE WALL THAT WOULD HAVE EXISTED THERE (instead of the hole!!) SHOULD HAVE FELT, with the fluid IN MOTION.

- total pressure is measured using a gauge with a hole normal to the flow direction, at the end of a tube, so it actually measures THE SAME FLUID pressure, in the same spot, but STATIONARY, so total pressure is the pressure that a wall would feel if the fluid was completely stationary.

Some people may get confused a little, and say something like: what about the stagnation point? Well, that's THE ONLY POINT where Pstatic=Ptotal in a moving fluid.

I hope this was a good enough explanation.

Best wishes, Razvan


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