Learning Forum

[Zen]

I want to perform an analysis of air recirculation and determine the percentage of dirty air that enters the intake duct (forcing fan system, 2 ducts) instead of exiting through the exhaust fan (green box). In this context, I encountered an error stating "floating point exception" (FIG. 2) and I suspect that there is a mistake in defining my boundary conditions (inlet, outlet, interior, wall). The boundary condition definitions I have made can be seen on FIG.1.
Can someone help me and tell me what I need to do so that I can run the calculation without any issues?

[Rob]

Have a look at the mesh. Just because the cell quality is (just about) acceptable doesn't mean the mesh is appropriate. You need to resolve the flow in the domain so where you have 3-4 cells across the duct/tunnel isn't good enough. You may want to review splitting surface in the geometry tool too as I don't think you need the stubs on the outlet. 

[Zen]

 

Thank you, I have resolved my issue by improving the mesh. I have another question regarding my case. I want my intake forcing duct to draw air from the inlet tunnel located at the bottom left and top right. What boundary condition should I use in your opinion? Would using a pressure outlet at the front of the duct represent this condition correctly? or using 'fan' boundary condition would suit it better?

 

[Rob]

If you're sucking air in use a pressure boundary. What property model are you using for air density? That may determine some of the solve settings to prevent fluid "falling" through the domain.