SimScale CAE Forum

Odd Behaviour in flow results


#1

Hello …

I have been using SimScale to do some simple CFD visualizations of relatively low speed water flows around simple bodies. i.e. https://www.simscale.com/projects/dstokes/plt_flow_response_1/
I do all the results visualization in Paraview.
I have noticed odd simulation behaviour for some rather simple flow conditions. In the example case, a simple fusiform body, dropping through water at speeds from 0.25, 0.5, 1.0 and 1.5 m per sec. Using a simple standard mesh, simple boundary conditions…nothing could be simpler. And, just looking at U in the results, I can see a believable flow field (viz with streamlines) from the simulation at 1.0 meter per second ( and U from about 0.6 to 1.2 m per sec). However if I try the same mesh, same orientation, same everything except the initial flow velocity at 0.25, 0.5 or 1.5 m per sec I vizualize a distorted flow field with instantaneous velocities exceeding 1000 meters per sec. I had first thought that the unit scale had changed from m per sec to mm per sec, but, the flow field is not accurate at all (I have done many such real world flow studies in water and wind tunnels so I am familiar with acceptable streamlines). I am new to SimScale so I suspect I must be doing something incorrect. I was trying to have a very simple test scenario hence the simple body and standard automatic mesh without refinements. It is troublesome because it looks ‘fine’ at 1 m per sec…


#2

Hi @dstokes!

First thought: Turn on Potential foam initialization in the Simulation Control and see what changes you can achieve inside the simulation. Tagging the @CFD-SQUAD in any case :slight_smile:

Keep us posted!

Jousef


#3

Will give it a try again at 1.5 m/s with the potential foam initialization activated.
Thanks!


#4

Setting the potential foam initialization to ON was successful. Thank you for the help. I apologize, if I had dug deeper into the forums I might have realized that others have experienced similar issues and that that was a potential solution.