# I have a problem about possion pressure equation

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 November 24, 2011, 10:41 I have a problem about possion pressure equation #1 New Member   kanzaki urumi Join Date: Nov 2011 Posts: 2 Rep Power: 0 hello everyone. I have a problem about my research. my prof. give me a problem to me that i need to resolve this week. my research is about PIV,now i have velocity in x,y axis(u and v) but i know don't how to calculate pressure from velocity i go find in google but i don't understand much, how to use possion pressure equation. i need to know how to use velocity to calculate pressure because i have to write C++ program to calculate its for me and compare to openfoam in next step. anyone have any idea about it pls help me and thank you very much guy. ps. i'm sorry if my english is not correct clz i'm not a native eng speaker.

November 24, 2011, 14:18
#2
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Arjun
Join Date: Mar 2009
Location: Nurenberg, Germany
Posts: 491
Rep Power: 13
Quote:
 Originally Posted by rainbow66 hello everyone. I have a problem about my research. my prof. give me a problem to me that i need to resolve this week. my research is about PIV,now i have velocity in x,y axis(u and v) but i know don't how to calculate pressure from velocity i go find in google but i don't understand much, how to use possion pressure equation. i need to know how to use velocity to calculate pressure because i have to write C++ program to calculate its for me and compare to openfoam in next step. anyone have any idea about it pls help me and thank you very much guy. ps. i'm sorry if my english is not correct clz i'm not a native eng speaker.

you have to derive continuity equation from velocity, which would be like poisson equation. Solve this by any matrix solver.

 November 25, 2011, 09:21 #3 New Member   Carlos Join Date: Nov 2011 Location: The Netherlands Posts: 17 Rep Power: 6 You indeed need the continuity equation. However that will not be sufficient as only rho and V are the only quantities embedded into the continuity equation. How to proceed largely depends on the type of flow you have. Could you give us some more specifics about the type of flow? If the flow is for example incompressible, you will need both the continuity and the momentum equation (in x and y direction). The momentum equation is a vector equation and gives you two equations in 2D. Along with the continuity equation you have then three equations in total. The unknowns are then u, v and p. Thus the system is solvable. __________________ "Do not worry about your difficulties in Mathematics. I can assure you mine are still greater." - Albert Einstein

November 25, 2011, 19:41
#4
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Arjun
Join Date: Mar 2009
Location: Nurenberg, Germany
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Quote:
 Originally Posted by Caluca You indeed need the continuity equation. However that will not be sufficient as only rho and V are the only quantities embedded into the continuity equation. How to proceed largely depends on the type of flow you have. Could you give us some more specifics about the type of flow? If the flow is for example incompressible, you will need both the continuity and the momentum equation (in x and y direction). The momentum equation is a vector equation and gives you two equations in 2D. Along with the continuity equation you have then three equations in total. The unknowns are then u, v and p. Thus the system is solvable.
i thought he/she said he/she knows u,v,w. If he/she does not know than I am afraid the assignment is too much for 1 week.

 November 26, 2011, 11:25 #5 New Member   kanzaki urumi Join Date: Nov 2011 Posts: 2 Rep Power: 0 thank you every one now i know how to solve it thank you for advice

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