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-   -   rotating wall inside of an MRF zone - fixedValue or movingWallvelocity? (https://www.cfd-online.com/Forums/openfoam-solving/63025-rotating-wall-inside-mrf-zone-fixedvalue-movingwallvelocity.html)

 evrikon March 26, 2009 06:29

rotating wall inside of an MRF zone - fixedValue or movingWallvelocity?

Hello together,

I simulate a simple axial fan with MRFSimpleFoam. Everithing works fine, however, I have got very low pressure jump predicted. I' looking now where mistake in my settings is.

The question is what the type of boundary condition I should use for the rotor. Rotor in my simulation is a rotating fan wall inside of the MRF zone and rotates of course with the same angular velocity as the whole MRF zone. If I would use fixedvalue; uniform (0 0 0) like in the tutorial mixerVessel2D, does it stay at rest? Should I take movingWallVelocity instead (s. below)?

From my ../0/U;
.....
boundaryField
{
STATOR
{
type fixedValue;
value uniform (0 0 0);
}

ROTOR
{
type movingWallVelocity;
value uniform (0 0 0);
...........

Other question for my full understanding: does MRF model in OF use an absolute velocity formulation or relative velocity formulation? "absolute" means it solves the equations still in non-rotating coordinate system, relative I mean as rotating coordinate system. This question refers to the problem I encountered, namely with absolute velocity formulation the wall should rotate, with relative should stay at rest relatively to the rotating zone where it is located in.

Alex

 evrikon April 17, 2009 08:21

Resolved

In the meantime I tried itself, read through the forum etc. If the case set up correctly fixed value condition for a wall inside of a rotating zone leads to correct radial velocity distribution on this wall. One can see it in paraview.

 nash November 28, 2013 15:02

hi evrikon,

sorry for bringing this old thread up.
do you manage to get the right pressure rise?
i simulate the radial fan now, and i got lower value of pressure rise. and the residuals of velocity fall only to 3rd order of magnitude.

for this simulation, i use approach of mrf and turbulence model laundersharma and komegasst (low re model implementation).

any suggestion for better result?

 be_inspired April 30, 2015 03:51

Quick question.
Did you make any faceZone? It is to know if boundary faces are selected or not ( including wall faces)

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