Learning Forum

[TSADEGHI]

Hello, 
I am using the DPM model to simulate the spray plume inside an L shape tube. The viscose model is K-w SST and I am using species transport which is just H2O and air. For boundary conditions, My inlet is defined as a pressure outlet, and my outlet is defined as a velocity inlet. In my simulation, I receive this error saying "floating point exception. Error Object: #f while I am getting regular convergence ( please see attached document). However, I am able to open another data file a few time steps before the error and by changing URF (just momentum) I can pass the error but it will happen again after a while. (let's say I receive the error after 350-time steps, so I open a file after 300-time steps and change the URF and run it again. This time for example I receive the error at 600-time step, so  I have to repeat the process again and again). Please help me to find what is the problem. I have already changed the number of meshs and made my cell size finer and it did not work. I have changed the viscose model and scheme and it did not work. Let me know if you need more information. 

Thank you!

[Rob]

As a guess you've got a load of particles stuck in the boundary layer somewhere and the energy/mass source is causing hot & cold spots. That'll eventually confuse the solver and diverge.  
Assuming you're looking at wet particles in a medical throat model use less refinement near the wall (you may want deeper near wall cells for DPM) and review the mesh: there's no need to use an O-grid in a modern solver, there's a reason we did all the work on the Fluent Meshing poly & poly-hexcore methods. 

[TSADEGHI]

Hello Rob, 

Yes, you are right; that is a medical throat model. Well, I could prevent the divergence (somehow) by using first-order discretization for the energy and the H2o phase. But it leads to less accurate results, which are not acceptable. 

Could you please explain what is an O-grid ? I couldn't find any helpful information in the manual. 

 

Also, I am getting dpm mass source data with positive and negative signs. What is the difference? Does the negative sign mean it is evaporated mass?