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When the velocity is small, the dynamic mesh doesn't move

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Old   January 3, 2011, 10:27
Default When the velocity is small, the dynamic mesh doesn't move
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My UDF is quite simple, but the velocity is very small:
DEFINE_CG_MOTION(plunge, dt, cg_vel, cg_omega, time, dtime)
cg_vel[0] = 1e-6;

When I set the time step size as 1s, the dynamic mesh moves correctly, but if I set the time step size as 0.1s, the dynamic mesh doesn't move. And with the time step size 0.1s but the velocity is 1e-5, the dynamic mesh can move again.

I guess that the product of velocity and time step size has to be larger than some particular value, but I don't know what this value is and how to change this value. I changed the mesh size and material, but the problem still exists.

Can someone help me? Thanks a lot.
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