Discussion Forum

Hello everyone,

I would like to make a model of a cylindrical, straight tube that pushes and sucks fluid from both sides. I need this to be an interactive model, as eventually the fluid will move valves at the ends of the tube, that will open and close passively to the flow. The whole system will be like a pump, where the valves allow unidirectional flow and prevent regurgitation.

In any case, I am a COMSOL beginner and I am trying to get the flow correct. I have tried sevelar approaches. To me, the approach that makes most sense is to use a prescribed mesh displacement at the part of the tube that contracts. I make a smooth, sinusoidal radius parameter to control the displacement (cosine oscillation 4um amplitude), but I end up getting the homogeneous solution (everything is zero). When I try adding a tube around the contracting section, representing a solid part that makes the tube contract, and apply a contraction through prescribed displacement of the solid, as soon as I reach time 0.35s (when the tube starts contracting), the simulation either crashes or becomes very very slow (time steps drop to 0.1ms).

Could you give me some direction on how to implement what I need? I am pretty sure this simulation is simple and I am doing something wrong. I have attached the model I made, without the solid section, using the prescribed mesh displacement. Eventually I will add the valves at the non-contracting spaces, hence I picked FSI.

Thank you for your time!