Define Contact for a moving sphere
 

Dear All,
I am conducting a detailed study on a 3D sphere travelling in a pipe filled with water. I managed to get it moving under transient conditions using a compiled UDF to simulate the motion. Unfortunately, the model cannot go any further than 1.70 seconds as the sphere hits the wall and I ended up with an error saying "Negative Cell Volume".
The problem can be solved if I could restrict the motion of capsule in such a way that the cells between sphere and bottom wall doesn't get collapsed.
Because of the lack of information regarding this new thing, I do need a help in creating a UDF to control the motion in 3D.
Please help.

HI Sufyan,
I am working on a smiliar problem using dynamic mesh, i am going through ansys tutorial of falling box using dynamic mesh ,the simulation is running perfectly ,but i want to get the velocity V/S time plot for the box, but all the outputs are regarding the fluid velocity and pressure..
Please let me know if you know how to get that..
Thanks
Subodh

Hi Subodh21

That sounded great actually, and I started with the same tutorial. However, I wonder what kind of problems you are working on. Is it in a horizontal plane, and what kind of geometry you conducted.

Any way, the UDF was such a headache to me and I am still having issues when the sphere touches the lower wall. Please communicate with me and keep discussing that.

Plotting velocity versus time can be done in two ways. You could either enable the motion history in the dynamic mesh settings, or from graphics and contours you can enable writing anything into a file.

Thanks a lot Sufyan.

Currently i have just started to learn Dynamic mesh basics using Ansys tutorials.
My ultimate aim is to model a spherical ice model moving due to buoyancy and hitting a steel structure and compare with actual results.

Thanks a lot i could get the velocity profile :)
Let me know if you have any further suggestions.

Thanks
Subodh

Sounds great Subodh21
 

Happy to help, no worries.
But, I am still wondering if you conducted controlling the motion of that sphere though. If you did, please tell me how you managed as I am struggling to define the contact region of the sphere in my model by using a proper UDF. No tutorials been provided for that, so please if you got any information regarding this tell me.
Thanks for sending me a friendship request by the way.
Cheers

Hi Sufiyan,

I am sorry to say i have recently stated working with dynamic mesh,so learning my way around and getting used to it.

I am still working with the tutorials ,not yet conducted motion control.

I have a question while making a geometry for a multiphase like in our case sphere in water with air at the boundary.
The tutorial just gives the mesh file, how did you go about making a multiphase model in design modeller (workbench), for this problem.Let me know if you get some time.

Thanks
Subodh

Hi friend,
I haven't seen that tutorial yet, where did you get it from. Could you pass it to me as it might be helpful for my work as well.
Regarding the geometry, you need to contact Ansys supporting team. So, get yourself registered on the portal and they will definitely reply you.
Regards,

Sure
what's your email id?