[chennak]

Hi OpenFOAM community,

I have a question about the velocity BCs for the case of oscillatingDisplacement boundary field.

To test, I have set up a simple case with an oscillating square with oscillatingDisplacement field with A=(0,1,0), w=6.28318. There is no other velocity field. Since the displacement is of the form "A*sin(w*t)", I expect the velocity to satisfy "A*w*cos(w*t)". However, this does not seem to be the case.

The velocity at t=0.25 should be zero but the simulation gives it as 0.197335 with dt=0.01 and 0.039486 with dt=0.002, which does not seem to match with the expected value, although it seems to converge as dt ->0.

So, I am curious to know how the velocity is calculated for moving boundaries with specified displacement.