|
[Sponsors] |
![]() |
![]() |
#1 |
New Member
Join Date: Mar 2012
Posts: 5
Rep Power: 14 ![]() |
Dear all,
I have some questions regarding a simple case for MRFSimpleFoam. I have a cylindrical domain in which one side is inlet, the other is outlet and in it there is a small fan that is rotating. Ideally, I want to let the fan determine the input flowfield. For this problem I used laminar flow which I plan to change it to turbulent when the inlet velocity is determined. I tried to use the following boundary conditions: Inlet U: zeroGradient p: zeroGradient Outlet U: zeroGradient p: fixedValue Walls U: fixedValue 0 p: zeroGradient With the above settings I cannot get convergence and in the flow field there are backflows happening in various areas of the domain, which seems logical due to U zeroGradient at inlet and outlet. I also tried to use pressureInletVelocity for U at the inlet but the results were worse. If I impose U: fixedValue at the inlet, then everything works and I get convergence quite quickly. Any ideas on this? |
|
![]() |
![]() |
![]() |
![]() |
#2 |
Senior Member
zaynah K.
Join Date: Jun 2012
Location: Mauritius
Posts: 138
Rep Power: 14 ![]() |
hi
have you been able to solve that? |
|
![]() |
![]() |
![]() |
![]() |
#3 |
New Member
Join Date: Mar 2012
Posts: 5
Rep Power: 14 ![]() |
I was able to solve the problem only when I had defined an inlet velocity.
I have not been able to solve the case if I want the fan to determine the inflow. |
|
![]() |
![]() |
![]() |
![]() |
#4 |
Senior Member
zaynah K.
Join Date: Jun 2012
Location: Mauritius
Posts: 138
Rep Power: 14 ![]() |
hi can you please explain to me how you had defined the inlet vel?
thnaks zaynah |
|
![]() |
![]() |
![]() |
![]() |
#5 |
New Member
Join Date: Mar 2012
Posts: 5
Rep Power: 14 ![]() |
for the case that worked you can either define e.g.
inlet { type fixedValue; value uniform (1 0 0); } or inlet { type surfaceNormalFixedValue; refValue uniform -1; } both of the above work. |
|
![]() |
![]() |
![]() |
![]() |
#6 | |
Senior Member
zaynah K.
Join Date: Jun 2012
Location: Mauritius
Posts: 138
Rep Power: 14 ![]() |
the (1 0 0)
1 define 1m/s in x drection right? but what does the Quote:
|
||
![]() |
![]() |
![]() |
![]() |
#7 |
New Member
B
Join Date: Oct 2012
Posts: 17
Rep Power: 13 ![]() |
surfaceNormalFixedValue uses the outward normal vector (the vector normal to your inlet, pointing outside of the domain). If you give it a value of -1, it should give you a velocity of 1 m/s into your cylindrical domain.
|
|
![]() |
![]() |
![]() |
![]() |
#8 |
Senior Member
Niels Nielsen
Join Date: Mar 2009
Location: NJ - Denmark
Posts: 556
Rep Power: 27 ![]() |
Pretty easy to let the fan determine the inflow.
U Code:
inlet { type pressureInletVelocity; phi phi; value uniform (0 0 0); } outlet { type inletOutlet; inletValue uniform (0 0 0); value uniform (0 0 0); } Code:
inlet { type totalPressure; p0 uniform 0; phi phi; U U; rho none; psi none; gamma 1.0; } outlet { type fixedValue; value $internalField; }
__________________
Linnemann PS. I do not do personal support, so please post in the forums. |
|
![]() |
![]() |
![]() |
![]() |
#9 |
New Member
Join Date: Mar 2012
Posts: 5
Rep Power: 14 ![]() |
Linnemann thank you very much.
totalPressure and pressureInletVelocity worked very well. Maybe I could have realized it after studying a little more the manual. From what I understand, totalPressure BC is linked with pressureInletVelocity, pressureInletOutletVelocity, etc conditions or the opposite? |
|
![]() |
![]() |
![]() |
![]() |
#10 |
Member
Aathavan
Join Date: Nov 2012
Posts: 70
Rep Power: 13 ![]() |
Hi Linnemann,
The explained boundary conditions are fine, but i have small doubt. how to define are where to define the quantity of the flow. If i want to define 5 m3/s. how to define this with the above given example BC. Thanks, Aadhavan |
|
![]() |
![]() |
![]() |
![]() |
#11 |
Senior Member
Niels Nielsen
Join Date: Mar 2009
Location: NJ - Denmark
Posts: 556
Rep Power: 27 ![]() |
Hi
With the above BC's you cant define the volume flow. Then you switch to the below BC's U Code:
inlet { type flowRateInletVelocity; flowRate constant 0.5; // m3/s for incompressible and kg/s for compressible value uniform (0 0 0); } outlet { type zeroGradient; } Code:
inlet { type zeroGradient; } outlet { type fixedValue; value $internalField; }
__________________
Linnemann PS. I do not do personal support, so please post in the forums. |
|
![]() |
![]() |
![]() |
![]() |
#12 |
Member
Aathavan
Join Date: Nov 2012
Posts: 70
Rep Power: 13 ![]() |
Hi Linnemann,
Thanks for your reply, This BC already i am using. I want to use pressureInletVelocity BC, if I use this, how can I understand that, at what flow rate it is the simulation is going on. in my case the fan is designed for 5m3/s, if I want to see the performance at different flowRate, can I use this BC (pressureInletVelocity), if so how can I implement it. thanks, Aadhavan Last edited by Aadhavan; November 23, 2012 at 14:58. |
|
![]() |
![]() |
![]() |
![]() |
#13 | |
New Member
k zhang
Join Date: Jun 2012
Location: China
Posts: 9
Rep Power: 14 ![]() |
Quote:
Hi Linnemann, i have some doubts with the U value of inlet. if write it like : type fixedValue; value uniform (0.5 0 0); OK? if i have a model like this: inlet U=0.5, outlet contact the atmosphere. the fluid flow from the inlet to the outlet. Attacted are the Pd and U , run the interFoam, wrong... can you give me some advises?P.jpg U.jpg |
||
![]() |
![]() |
![]() |
Tags |
bcs, boundary conditions, mrfsimplefoam |
|
|
![]() |
||||
Thread | Thread Starter | Forum | Replies | Last Post |
Suggestions on Mesh and Schemes for MRFSimpleFoam | mixer | OpenFOAM Running, Solving & CFD | 3 | September 1, 2009 10:50 |