How do I properly set outlet conditions?

- November 9, 2019 at 1:56 pm
  
  Bran
  Subscriber
  
  Hello,
  
  I have been using pressure-outlet for my simulation, but I often find during the calculation, that there is Reversed flow on 31 faces (13.1% area) of pressure-outlet 70.
  
  As well as this, I am unsure if this flow reversal leads to turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 28 cells, which results in divergence.
  
  In the dialog box for pressure-outlet, there are turbulence parameters and gauge pressures, I am wondering how to best understand what conditions to put there.
  
  My scenario is cold air entering a closed container with the intent to cool heat generating components.
  
  The pressure outlet is placed in a location close to the inlet, as it is modelling an air conditioner into the container, a picture is shown.
- November 12, 2019 at 1:50 pm
  
  Rob
  Forum Moderator
  
  The aim is to avoid reverse flow. However, in this case I suspect it's always going to happen, so prevention isn't really an option. It's also a finding for your report.
  
  The viscosity ratio doesn't tend to cause divergence (I regularly hit it and/or increase to run a model), more likely you've not resolved something due to the mesh. Post some images and (hopefully) someone can help you. I'd suggest velocity contours with & without node values as a starting point.
- November 12, 2019 at 8:26 pm
  
  Bran
  Subscriber
  
  Thank you for your suggestion. A mesh refinement at the inlets and outlets has resolved this problem