ideal gas law and imcompressible ideal gas

- July 25, 2020 at 3:52 am
  
  Weiqiang Liu
  Subscriber
  
  Hi all,
  
  During my recent simulation work, I found an interesting thing. That is if I use imcompressible ideal gas to calculate density of mixture, results would be a mess. In other words, results are very unreasonable. However, if I use ideal gas law as density method, results would be very reasonable.
  
  Ps: I used laminar flow in my model.
  
  I am wondering why would this happen?
  
  Best regards
  
  Weiqiang
- July 27, 2020 at 3:23 pm
  
  RK
  Ansys Employee
  
  Hi Weiqiang,
  
  Note the difference between using the incompressible and the ideal gas model for density. For the incompressible ideal gas, the density is a function of only the operating pressure where as for the ideal gas law, density is a function of the sum of operating pressure and gauge (local) pressure.
- July 30, 2020 at 7:51 pm
  
  DrAmine
  Ansys Employee
  
  That is obvious especially in case of closed cavities or flow underlying strong pressure variations.n
- August 6, 2020 at 2:22 am
  
  Weiqiang Liu
  Subscriber
  
  Hi all,nReplying to individual comment is not allowed in new version of this forum? Anyway, thank your guys for giving me suggestions!nBest regardsnweiqiangn