[lacunacoil]

Dear Sir/Madam,

I am trying to do LES simulation for supersonic combustion in combustion chamber. Would you recommend us to use solve/initialize/init-instantaneous-vel command while we are doing RANS simulation with volumetric reaction and after solution convergence change viscous model to LES or do we have to simulate cold flow RANS, solve/initialize/init-instantaneous-vel command, switch to LES simulation and open volumetric reactions?

Sincerely

[LoGaL]

Solve the RANS with the flame first, then turn on LES.

[LuckyTran]

It doesn't have to even be a converged RANS. But I would still put the flame in the RANS. You don't want to ignite it in LES because there's a good chance the flame will blowout because it's not anchored, or it'll flashback and go to places where you don't want it to go. Better to just have a reasonable flame shape from RANS and minimize these risks.

[LoGaL]

If the swirl is very high, It can also happen that you can't get a converged steady RANS, but still, ignite it before switching to LES