Large velocity error near sliding mesh interface
 

Hi all,

So I'm running CFD simulations of a helicopter rotor in ANSYS CFX. I'm using a sliding mesh interface with and outer stationary region and an inner rotating region. I'm also using a k-omega turbulence model and have enabled `alternate rotation model'.

Near the sliding mesh interface I'm getting a large velocity error. I've attached an image showing a cross section of velocity contours and vectors. The large velocity error is quite clear and is occurring in a region where I would expect the velocity to be very close to zero.

I'm not sure if the source of this error is the sliding mesh interface itself, or if it has something to do with how CFX adds the rotational component of velocity to the flow within the rotating region.


I'd really appreciate any help I can get with this problem!

Cheers, David.

Are you showing velocity or velocity in the stationary frame - in other words, are you aware of this FAQ: http://www.cfd-online.com/Wiki/Ansys...f_reference.3F

I think that FAQ is talking about a different issue, btu I just want to be sure you are aware of this.

Do you get these spurious velocities when you do not use alternate rotation model? Also, have you tried a tighter convergence tolerance?

The contours are velocity in the stationary frame (not local frame).

My understanding is that the alternate rotation model uses the stationary frame velocity (rather than the local frame) to calculate advection. When I disable it I get a wildly inaccurate result throughout the rotating region (not just near the interface).

I'll try adjusting the convergence limit - will let you know how I get on.

Thanks for your help.