Learning Forum

[Saeed]

Hi,

 

I am seeing a convergence issue with my CFD-DEM coupling simulation. first that i run my fluent to get my case and data all the parameters converge with 10 iterations . when I use those case and date for the Rocky, beginning of the simulation all converge in 10 iterations but as simulation goes on it needs more iterations to converge( 30 to 40) and that is just for the continuty the rest converge with a few iterations. i tried lowering the time step and still it is happaning. what should i do that during the whole simulation continuty converge as it does beginning of the simulation?

Thanks 

[Rob]

You need to review the flow and see what's going on in the Fluent model. It could be the jump in source term from Rocky is a problem, but could just be you're triggering something in the flowfield that's causing the problem. 

[Saeed]

Dear Rob,

Thank you for your help. I have attached my velocity contour and vectors. can you please let me know what do you think about them ?

Also, how can I check  rocky source term or what is triggering flow field? 

[Rob]

I think you need to post process in Fluent. CFD Post always takes the wrong velocity formulation (relative/absolute) by default. Plot once with node values on, and once with them off. 

[Saeed]

Dear Rob,

Attached is the plots in fluent

 

[Rob]

It looks like the mesh could do with some refinement. How does the contact area look for the nonconformal? 

[Saeed]

Dear Rob,

This is how my mesh looks like. 

[Rob]

How does the mesh vary over the interface? More resolution may be needed given the apparent vortex that's forming.