About First order and second order upwind

arslandogukanitu · February 7, 2019, 01:47

Hi everyone,

I have a obstacle about convergence. I simulated 8/9 analysis about microchannel but other one (1/9) is not converged. In first order upwind scheme, it can be converged but in second order it cannot be converged. What should ı do?

For initial value, can ı use first order to solve in second upwind?

AliE · February 7, 2019, 03:32

Hi,

First order upwind is very diffusive and might shut down some instabilities (real or purerly numerical) that may impact the convergence. Restarting with the upwind field and switch to 2nd order can help. In any case does your case admit a steady solution or you have something like wake or vortex? A sketch of your problem might help!

FMDenaro · February 7, 2019, 03:34

Steady or unsteady simulation? In the latter case what about the time integration?

February 7, 2019, 01:47	About First order and second order upwind	#1
arslandogukanitu New Member Doğukan Arslan Join Date: Dec 2018 Posts: 2 Rep Power: 0	Hi everyone, I have a obstacle about convergence. I simulated 8/9 analysis about microchannel but other one (1/9) is not converged. In first order upwind scheme, it can be converged but in second order it cannot be converged. What should ı do? For initial value, can ı use first order to solve in second upwind?

February 7, 2019, 03:32		#2
AliE Senior Member Join Date: Dec 2017 Posts: 153 Rep Power: 8	Hi, First order upwind is very diffusive and might shut down some instabilities (real or purerly numerical) that may impact the convergence. Restarting with the upwind field and switch to 2nd order can help. In any case does your case admit a steady solution or you have something like wake or vortex? A sketch of your problem might help!

February 7, 2019, 03:34		#3
FMDenaro Senior Member Filippo Maria Denaro Join Date: Jul 2010 Posts: 6,776 Rep Power: 71	Steady or unsteady simulation? In the latter case what about the time integration?