|April 24, 2011, 07:50||
Unphysical behaviour in dynamic mesh/vof model
Join Date: Oct 2009
Posts: 11Rep Power: 7
I've been experimenting with dynamic meshes for a while, but, however, was not able to calculate the simple example described below.
I am trying to let a cylinder (diameter 25mm) fall into water (pressure based/vof geo reconstruct/piso)
The whole domain is a 0.3x0.3m face with the cylinder falling from a height of 0.0625m into the water. (approx. 65000 tri elements) There is also a hex boundary layer around the cylinder. The motion is introduced with the 6dof solver and an appropriate udf.
I calculated the mass and moments of inertia of the cylinder assuming a depth of 1m. The density is around 612 kg/m^3.
Problem: The calculation is doing fine until the cylinder dips into the water(with a velocity of about 1 m/s). Then it suddenly accelerates and bounces off the water surface like a rubber ball (velocity ~3m/s), until it crashes at the upper side of the domain.
The UDF i use is pretty the same as from the UDF tutorial:
DEFINE_SDOF_PROPERTIES(stage, prop, dt, time, dtime)
prop[SDOF_MASS] = 0.30;
prop[SDOF_IXX] = 0.025;
prop[SDOF_IYY] = 0.025;
prop[SDOF_IZZ] = 0.000234;
printf ("\nstage: updated 6DOF properties");
I have uploaded a video to http://www.it-satisfies.com/bouncing.mpeg
Any help will be highly appreciated.
|dynamic mesh, fluent vof|
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