
[Sponsors] 
June 13, 2008, 05:07 
If the pressure equation that

#21 
New Member
Roberto
Join Date: Mar 2009
Posts: 17
Rep Power: 8 
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! Roberto 

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

#22 
Senior Member
Niels Gjoel Jacobsen
Join Date: Mar 2009
Location: Deltares, Delft, The Netherlands
Posts: 1,660
Rep Power: 25 
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
__________________
Please note that I do not use the Friendfeature, so do not be offended, if I do not accept a request. 

June 13, 2008, 14:18 
The pressure field shown varie

#23 
New Member
Roberto
Join Date: Mar 2009
Posts: 17
Rep Power: 8 
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... Roberto 

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

#24 
Senior Member
Niels Gjoel Jacobsen
Join Date: Mar 2009
Location: Deltares, Delft, The Netherlands
Posts: 1,660
Rep Power: 25 
Please note the 'x' after u_0.
 Niels
__________________
Please note that I do not use the Friendfeature, so do not be offended, if I do not accept a request. 

June 14, 2008, 05:22 
i missed that parsicular! i've

#25 
New Member
Roberto
Join Date: Mar 2009
Posts: 17
Rep Power: 8 
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?
Roberto 

March 10, 2010, 12:38 

#26 
Senior Member
Kevin Smith
Join Date: Mar 2009
Posts: 103
Rep Power: 8 
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.


March 10, 2010, 12:42 

#27 
Senior Member
Kevin Smith
Join Date: Mar 2009
Posts: 103
Rep Power: 8 
Also, the field phi is a scalar field  taking divergence of that field seems nonsensical.. What am I missing?


March 17, 2010, 08:55 
Modeling the flow inside an annulus?!

#28 
New Member
Sawi
Join Date: Mar 2010
Posts: 7
Rep Power: 7 
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 

March 17, 2010, 16:25 

#29  
Senior Member
Sebastian Gatzka
Join Date: Mar 2009
Location: Frankfurt, Germany
Posts: 729
Rep Power: 11 
Quote:
Open you own discussion!
__________________
Schrödingers wife: "What did you do to the cat? It's half dead!" 

March 17, 2010, 18:33 

#30 
New Member
Sawi
Join Date: Mar 2010
Posts: 7
Rep Power: 7 
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...


March 17, 2010, 19:44 

#31 
Senior Member
Cean
Join Date: Feb 2010
Posts: 128
Rep Power: 7 
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. 

March 25, 2010, 12:32 

#32 
Senior Member
Kevin Smith
Join Date: Mar 2009
Posts: 103
Rep Power: 8 
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.


April 2, 2010, 08:43 

#33  
Senior Member
Cean
Join Date: Feb 2010
Posts: 128
Rep Power: 7 
Quote:
Does the equation means flux due to pressure change in the cell? 

April 6, 2010, 09:25 

#34 
Senior Member
Kevin Smith
Join Date: Mar 2009
Posts: 103
Rep Power: 8 
By phi I really meant potential, sorry for the confusion.


May 11, 2010, 01:52 
Cylindrical boundary condition

#35 
New Member
Joseph
Join Date: Mar 2010
Posts: 14
Rep Power: 6 
Hi
Could you send me your code about cylindrical boundary condition? TANX Joseph 

May 11, 2010, 02:58 
Hi

#36 
Senior Member
ata kamyabi
Join Date: Aug 2009
Location: Kerman
Posts: 322
Rep Power: 9 
Hi
I think that in that file which I have send for you, is a link to cylindrical B.C. Best regards 

Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
3d mesh gambit (cylinder within a cylinder)  Jason  ANSYS Meshing & Geometry  29  October 30, 2015 09:59 
tutorial for solving oscillating cylinder problem  CH  FLUENT  8  April 2, 2014 10:56 
tutorial 6 in Fluent 6.2 tutorial and Mesh  pilli4u  FLUENT  2  April 2, 2007 05:09 
tutorial for 3D CYLINDERPISTON ARRANGEMENT  sachin bhalerao  FLUENT  0  February 28, 2006 04:05 
Help meeee: Wave cylinder (sine cylinder)  Ngoctq  FLUENT  0  December 29, 2005 21:46 