Reduce Damping
I am trying to simulate propellant slosh in a sphere tank which I'm comparing to experimental data. I am trying to validate my model by comparing the damping coefficient and frequency. It seems that my model has a very high damping coefficient compared to the experiment. I've calculate a damping ratio of around 0.02 where the experiment showed 0.004 (about 5 times smaller).
I've tried to reduce the damping by lower viscosity (artificial), decreasing/increasing particle spacing (dp), varying coef. speed of sound (10-30). I've also used the beta DualSPHysics 3.0 and applied delta SPH (=0.1).
The sphere that my fluid is in is pretty small with a radius around 0.1 meters. I've kept my particle spacing around 0.0007-0.002. I've run cases in both 2D and 3D and find similar results over an over damped system.
Any help that anyone may have would be extremely helpful.
Thank you.
I've tried to reduce the damping by lower viscosity (artificial), decreasing/increasing particle spacing (dp), varying coef. speed of sound (10-30). I've also used the beta DualSPHysics 3.0 and applied delta SPH (=0.1).
The sphere that my fluid is in is pretty small with a radius around 0.1 meters. I've kept my particle spacing around 0.0007-0.002. I've run cases in both 2D and 3D and find similar results over an over damped system.
Any help that anyone may have would be extremely helpful.
Thank you.
Comments
I'm wondering, what do you have the X-SPH coefficient set to? Perhaps try setting it to zero and seeing if your simulation remains stable as this can be a source of effective drag.
Yes I have set my X-SPH value to zero. I've actually I had the most success by increasing the coefficient value from 0.866025 to around 1.7. I believe that this allows particles to properly transfer their velocities to their neighbors. I think the only potential problem with this is that the boundaries could affect their neighboring particles more and slow them down but it doesn't seem to be an issue for me. Actually, this may create a sort of artificial wetting effect which I would like to have in my simulation.
Thank you for the input