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Old   June 13, 2008, 05:07
Default If the pressure equation that
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If the pressure equation that potentialFoam solves is not laplacian(p)=0 then the manual should be corrected!

From the relation I've posted after some rearrangements it turns:

laplacian(p)=-rho*(d^2(phi)/(d(x_i)d(x_k)))^2

wich is different from the equation that you have posted. Also laplacian(p)=div(phi) is not dimensionally correct! and also: is it possible to define the divergence of a scalar field?

nice weekend to you!

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Old   June 13, 2008, 10:14
Default Hi I am wondering if we are
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Hi

I am wondering if we are chasing something which is not present in the solution. Have found the analytical solution of the potential around a cylinder, and it writes:

phi = -u_0 x (1 + R^2 / (x^2 + y^2))

Thus in increases for decreasing x and varies linearly in the farfield of the cylinder. Could it be that the solution is actual for phi and not p?

/ Niels
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Old   June 13, 2008, 14:18
Default The pressure field shown varie
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The pressure field shown varies linearly in the whole field, not only in the farfield. I don't know exactly what is the solution for the potential flow but if it is the one that you write you can write it in polar coordinates as:

phi=-u_o*(1+R^2/r^2)

where r^2 is the generical radius far from the cylinder. In this way the potential contours must be concentrical circles around the cylinder... and this is not the case of the field shown. So the pressure field shown is not the potential field...

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Old   June 14, 2008, 03:56
Default Please note the 'x' after u_0.
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Please note the 'x' after u_0.

- Niels
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Old   June 14, 2008, 05:22
Default i missed that parsicular! i've
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i missed that parsicular! i've plotted the function you posted and it shows good agreement with the pressure field shown... but why potentialFoam plots the potential field instead of the pressure field?

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Old   March 10, 2010, 11:38
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Did this issue ever get resolved? Both tutorials for potentialFoam seem to give incorrect pressure distributions if you run the simulation with the '-writep' argument. It does seem the pressure field resembles phi more than anything.
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Old   March 10, 2010, 11:42
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Also, the field phi is a scalar field - taking divergence of that field seems nonsensical.. What am I missing?
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Old   March 17, 2010, 08:55
Default Modeling the flow inside an annulus?!
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I' am trying to model the behavior of a non newtonian fluid inside an eccentric annulus. I need to get a profile of the annular velocity of the fluid for the whole cross section. I just discovered the OpenFoam and i was wondering if the "nonNewtonianIcoFoam" solver would manage a problem like this? Since i am new in this area any further help or suggestions is appreciated. What should i read to get started? Is there another solver that is more specialized in Annular flow? Will i need a mesh generation program(Boundary conforming grid generator) or Will the Openfoam handle the whole problem?

Really appreciate any help
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Old   March 17, 2010, 16:25
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Quote:
Originally Posted by Aelsawis View Post
I' am trying to model the behavior of a non newtonian fluid inside an eccentric annulus. I need to get a profile of the annular velocity of the fluid for the whole cross section. I just discovered the OpenFoam and i was wondering if the "nonNewtonianIcoFoam" solver would manage a problem like this? Since i am new in this area any further help or suggestions is appreciated. What should i read to get started? Is there another solver that is more specialized in Annular flow? Will i need a mesh generation program(Boundary conforming grid generator) or Will the Openfoam handle the whole problem?

Really appreciate any help
I'm pretty sure your question is in not related to this thread.
Open you own discussion!
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Old   March 17, 2010, 18:33
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yeah maybe ur right i am sorry for the disturbance.i just thought since the discussion began with the cylinder example ..that maybe someone would know something about the annular flow between two cylinders...
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Old   March 17, 2010, 19:44
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The p in the program has a dimension of m^2/s^2, so it is not simple a pressure. I think it is p/density. Becasue:

p - kg/(ms^2)
density - (kg/m^3)

p/density=kg/(ms^2)/(kg/m^3)=m^2/s^2

For potential flow, usually we start from solving phi, then get U by differentiation of phi. Then get pressure from Bernolli's equation. The U is correct here, so we could try to get pressure from it.

BTW, There is an analyticalFoam folder under the cylinder tutorial folder. Where this output is saved?

Cean

Last edited by shirazbj; March 18, 2010 at 23:45.
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Old   March 25, 2010, 12:32
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Cean - That's what I ended up doing - since my case had a uniform free stream velocity it was relatively trivial to modify the potentialFoam solver to calculate pressure.
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Old   April 2, 2010, 08:43
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Quote:
Originally Posted by kev4573 View Post
Did this issue ever get resolved? Both tutorials for potentialFoam seem to give incorrect pressure distributions if you run the simulation with the '-writep' argument. It does seem the pressure field resembles phi more than anything.
phi is the flux through the cell surface.

Does the equation means flux due to pressure change in the cell?
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Old   April 6, 2010, 09:25
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By phi I really meant potential, sorry for the confusion.
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Old   May 11, 2010, 01:52
Default Cylindrical boundary condition
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Hi
Could you send me your code about cylindrical boundary condition?
TANX
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Old   May 11, 2010, 02:58
Default Hi
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Hi
I think that in that file which I have send for you, is a link to cylindrical B.C.
Best regards
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