rotatingWallVelocity bc
Hi Foamers,
i try to calculate a flow between two cylinders. The inner cylinder is rotating so i used the rotatingWallVelocity bc for the inner wall. My 0/U file: dimensions [0 1 -1 0 0 0 0]; internalField uniform (0 0 0); boundaryField { movingWall { type rotatingWallVelocity; origin (0 0 0); axis (0 0 1); omega 25; } fixedWall { type fixedValue; value uniform (0 0 0); } frontandback { type empty; } } Paraview shows that the rotating wall velocity is exact twice bigger then expected. The diameter of the inner cylinder is 0.035 m OpenFoam wall velocity 0.875 m/s. What is the unit of omega in the U ? Thanks an best regards Lodda |
velocity (m/s) = omega (1/s) * radius (m)
Are you using the cylinder diameter or the radius to compute the rotational velocity? That could be why your velocity is twice as big as you were expecting. |
The OpenFoam result for the rotating wall velocity is 0.875 m/s. I expected according to v = omega * r = 25 * 0.0175 = 0.4375 m/s. I dont know what is wrong.
boundaryField { movingWall { type rotatingWallVelocity; origin (0 0 0); axis (0 0 1); omega 25; value nonuniform List<vector> 200 ( (0.0137422 -0.874784 0) (0.0412131 -0.873921 0) (0.0686432 -0.872195 1.86596e-27) (0.0960057 -0.869609 -0) (0.123273 -0.866164 0) (0.150419 -0.861864 0) This are the components of the calculated velocity. The magnitude at the rotating wall is always 0.875 m/s. http://img21.imageshack.us/img21/8669/rotcylinder.jpg Best regards Lodda |
Ok, one thing to check (which I am sure you have done) is that the diameter you are using is correct. Second is to make sure your origin is in the right place. What am I looking at in the image? Do you have a cylinder within a cylinder? Apart from this, I'm a bit stumped tbh. I have it working without an issue on a more complex problem that this one.
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This are two cylinders and the inner cylinder is rotating with omega = 25 as explained above and thats it.
Sorry, i checked my blockMeshdict the diameter is wrong! Thanks for answering :) |
Heh, no worries. It's a surprisingly easy mistake to make!
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Lodda, I'm trying to simulate cylinder with rotating bottom, filled with a viscous laminar incompressible fluid. Your case is very similar to mine. Maybe you could send me your files, because I'm new to OpenFOAM, and can not figure out how I do it.
Sorry for my English :) |
train moving in tunnel
hello ,
can any body help me as i am getting floating error: invalid number. my email sheikhnasir39@gmail.com with regards:confused: |
Quote:
I am wanted ask to what do you mean by 'make sure your origin is in the right place'? I also have an annulus-type geometry in which the inner cylinder is rotating. Also, if we look at the source code: const vectorField Up ( (-om)*((patch().Cf() - origin_) ^ (axis_/mag(axis_))) ); Shouldn't the distance be the perpendicular distance from the axis rather than the distance between the face center and the origin? Thanks Viraj |
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