CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   FLUENT (http://www.cfd-online.com/Forums/fluent/)
-   -   When the velocity is small, the dynamic mesh doesn't move (http://www.cfd-online.com/Forums/fluent/83552-when-velocity-small-dynamic-mesh-doesnt-move.html)

li2150 January 3, 2011 11:27

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


All times are GMT -4. The time now is 15:29.