I'm trying to simulate a rigid object moving in a rigid fluid-filled channel in COMSOL. The inlet provides a velocity for the non-compressible fluid, which pushes the object. No problem so far, this works fine for time-dependent studies in 2D.
The issue is that I want to move to 3D, and I think that will become very computationally expensive. It was suggested that I use snapshots of static studies (it's Stokes flow, so supposedly that's ok -- regardless, that's a different issue), rather than doing time-dependent studies. But, a static study won't converge (which makes sense because there is no steady state given the continuous movement of the object down the channel).
I was told the solution to this was to use a moving wall. I have spent hours trying to figure out how to do this, and learned nearly nothing. The 1000+ page COMSOL reference guide has one paragraph on moving walls, and essentially says "If you use a moving wall, u = u sub w." Not very informative.
I would greatly appreciate it if someone could explain the theory of a moving wall in general (why and when is it used), and how it applies to this problem specifically (where does the wall go, and what are the parameters).
Thank you!
The issue is that I want to move to 3D, and I think that will become very computationally expensive. It was suggested that I use snapshots of static studies (it's Stokes flow, so supposedly that's ok -- regardless, that's a different issue), rather than doing time-dependent studies. But, a static study won't converge (which makes sense because there is no steady state given the continuous movement of the object down the channel).
I was told the solution to this was to use a moving wall. I have spent hours trying to figure out how to do this, and learned nearly nothing. The 1000+ page COMSOL reference guide has one paragraph on moving walls, and essentially says "If you use a moving wall, u = u sub w." Not very informative.
I would greatly appreciate it if someone could explain the theory of a moving wall in general (why and when is it used), and how it applies to this problem specifically (where does the wall go, and what are the parameters).
Thank you!