Implicit ddt and Courant Number

Aleksey_R · February 9, 2010, 13:17

Hello, colleagues.
Please, help me with the following problem.
I'm solving transport equations (convection + diffusion) for some species using Euler implicit representation of time derivative term (fvm::ddt in solver code and Euler scheme fvSchemes). Such implicit scheme must be unconditionally stable. Why anything crashes if Courant number > 1? I mean iterative process in solving discretized equations diverges.
And please, tell me, is there in OpenFOAM of method to solve Navier-Stokes equations for laminar flow, which lets to set Courant number > 1?

Best regards, Aleksey.

betakv · February 12, 2010, 04:41

Hi Aleksey,

try to use solver pimpleFoam. It's stable for Co > 1.

Vojta

February 9, 2010, 13:17	Implicit ddt and Courant Number	#1
Aleksey_R Member Aleksey Rukhlenko Join Date: Nov 2009 Location: Moscow Posts: 55 Rep Power: 16	Hello, colleagues. Please, help me with the following problem. I'm solving transport equations (convection + diffusion) for some species using Euler implicit representation of time derivative term (fvm::ddt in solver code and Euler scheme fvSchemes). Such implicit scheme must be unconditionally stable. Why anything crashes if Courant number > 1? I mean iterative process in solving discretized equations diverges. And please, tell me, is there in OpenFOAM of method to solve Navier-Stokes equations for laminar flow, which lets to set Courant number > 1? Best regards, Aleksey.

February 12, 2010, 04:41		#2
betakv Member Vojtech Betak Join Date: Mar 2009 Location: Czech republic Posts: 34 Rep Power: 18	Hi Aleksey, try to use solver pimpleFoam. It's stable for Co > 1. Vojta