how is rhoSimpleFoam a compressible steady statefor compressible flow

cleoo · September 21, 2016, 10:48

how can rhoSimpleFoam be a compressible solver and a steady state solver at the same ime?

From what I know (please correct me if I am wrong)
If its a compressible solver it means it takes into account that density is changing.
if its a steady state you don't take time into account.

so there comes my confusion it seems like the two are contradicting each other.

hunger · September 22, 2016, 04:00

The density can change in space, e.g. due to a certain temperature field present in your geometry. It can be stationary though, if in every single control volume, the density does not change over the time.

Another example: if you consider a steady-state solution for your velocity field, it doesn't mean that your velocity has to be constant in all your simulation domain. If the cross-section of a pipe gets smaller, the flow velocity will increase (assuming incompressible flow). This change in velocity is not connected with the time.

Best regards
Harald

cleoo · September 22, 2016, 04:23

thanks, that makes sense and great name 'hunger'

September 21, 2016, 10:48	how is rhoSimpleFoam a compressible steady statefor compressible flow	#1
cleoo Member annn Join Date: Jun 2016 Posts: 40 Rep Power: 10	how can rhoSimpleFoam be a compressible solver and a steady state solver at the same ime? From what I know (please correct me if I am wrong) If its a compressible solver it means it takes into account that density is changing. if its a steady state you don't take time into account. so there comes my confusion it seems like the two are contradicting each other.

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September 22, 2016, 04:00		#2
hunger New Member Join Date: Oct 2015 Location: Austria Posts: 9 Rep Power: 11	The density can change in space, e.g. due to a certain temperature field present in your geometry. It can be stationary though, if in every single control volume, the density does not change over the time. Another example: if you consider a steady-state solution for your velocity field, it doesn't mean that your velocity has to be constant in all your simulation domain. If the cross-section of a pipe gets smaller, the flow velocity will increase (assuming incompressible flow). This change in velocity is not connected with the time. Best regards Harald

September 22, 2016, 04:23		#3
cleoo Member annn Join Date: Jun 2016 Posts: 40 Rep Power: 10	thanks, that makes sense and great name 'hunger'