Reply To: Tutorial or Help for 2 way FSI

[Paul Hutcheson]

Are you not modelling the lubricant in CFD? Is it just air? Sorry I misunderstood this.

If you are not modelling the lubricant film I agree, you need frictional contact to drive rotation instead. If you can assume no mechanical slip/lubricant slip, you can choose "rough" contact, which will rotate the ball exactly at the same speed as the IR with no slip. Otherwise this is a modelling uncertainty and the ball may drift as I think I saw in one of your videos.

Do you want to create an animation or find an engineering solution? You can do it all with moving mesh but it won't be as efficient to run as you'll need the full 360 deg. or rotate both fluid and mechanical sectors, possibly leading to errors down the line. This is why we solve rotating cases in rotating frame wherever possible.

As for the fluid forces, you need to monitor the ball torque. It's not possible to evaluate whether or not the ball should move based on the velocity or pressure field. We can imagine, but with the torque, and the rotational moment of inertia we can predict the rotation of the ball and know if it's a setup error or not.

Paul