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rotatingWallVelocity normal to wall

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Old   June 21, 2012, 07:00
Default rotatingWallVelocity normal to wall
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Robert Castilla
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Hi,

I am working in a simulation with dynamic mesh. But, previously, I wanted to make the stationary simulation. A wall is rotating, and I wonder if I could use the rotatingWallVelocity. I tried with pimpleFoam, and the results are not correct (very high velocities in some cells, near to the rotating wall). Even with potential Foam, it gives velocity zero (no wall velocity?) around the domain, except on the wall.

I checked the rotatingWallVelocity BC source and I found that:


// Remove the component of Up normal to the wall
// just in case it is not exactly circular
const vectorField n(patch().nf());
vectorField::operator=(Up - n*(n & Up));



Does it mean that only the tangencial wall velocity is considered for the fluid motion? Why? Anyway, I will try to remove this constraint, and I see what happens... but I would like to know the reason of that.

Thanks

Robert
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Old   June 21, 2012, 16:21
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Kyle Mooney
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Quote:
Originally Posted by rcastilla View Post
Hi,

I am working in a simulation with dynamic mesh. But, previously, I wanted to make the stationary simulation. A wall is rotating, and I wonder if I could use the rotatingWallVelocity. I tried with pimpleFoam, and the results are not correct (very high velocities in some cells, near to the rotating wall). Even with potential Foam, it gives velocity zero (no wall velocity?) around the domain, except on the wall.

I checked the rotatingWallVelocity BC source and I found that:


// Remove the component of Up normal to the wall
// just in case it is not exactly circular
const vectorField n(patch().nf());
vectorField:perator=(Up - n*(n & Up));



Does it mean that only the tangencial wall velocity is considered for the fluid motion? Why? Anyway, I will try to remove this constraint, and I see what happens... but I would like to know the reason of that.

Thanks

Robert
I believe that this boundary condition is made for circular boundaries and to act as if it were a no slip no penetration rotating wall, as you described. Because it is a 'wall' no penetration is implied, hence the removal of the face normal component of the velocity. This is a relatively straight forward velocity boundary condition. I doubt that your issues with running it in conjunction with pimpleFoam are related to a bug or something to that nature.
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