combustion third order time accuracy using runge kutta method
 

Hello everyone,


This is the follow up post of my earlier thread as i didn't find error after long check out. However i realized that there is no combustion(no reaction and no heat release )in the simulation so i am getting lower temperature. Combustion was working fine before upgrading time accuracy using rk4 method.



i checked chemistry properties and combustion both are on and true. Also i am using "rhoCombustionModel" . can anyone suggest possible solution or error on the fomulation of species and energy equation specially involving reaction. Thank you.





I was facing the problem with time accuracy of the solution using first order Euler ddt. So, i thought of implementing rk4 third order time accuracy. Following represents the
equations:

rho = rhoOld + rkCoef[cycle] *runTime.deltaT()*(-fvc::div(Riemann.rhoFlux()))


momentum equations.
rhoU = rhoUOld + rkCoeff[cycle]*runTime.deltaT()*(-fvc::div(Riemann.rhoUFlux())+fvc::div(tauMC)+fvc:: laplacian(muEff, U));



species transport eqn:
fvScalarMatrix YiEqn
(
rhoYi - rhoYOldi
- rkCoeff[cycle]*runTime.deltaT()*(-fvc::div(Riemann.rhoScalarFlux(i))+
fvm::laplacian(turbulence->muEff(), Yi))
== rkCoeff[cycle]*runTime.deltaT()*reaction->R(Yi)
);


energy eqn


rhoE = rhoEOld + rkCoeff[cycle]*runTime.deltaT()*(
--fvc::div(Riemann.rhoEFlux() + fvc::div(sigmaDotU) + fvc::laplacian(turbulence->alphaEff(), h)
+fvc::laplacian(k,T)+reaction->Sh());

OF2.3.1


courant number and timesteps are calculated as per rhocentralFoam.






Thank you all.