[Senbonzakura]

I am extremely new to CFD. This question might be silly, but in several solving methods we need to iterate the scheme at each time step multiple times to make it converge and then move on to the next one (like Roe Solver). But, the schemes like Maccormack, Richtmeyer, Lax Friedrichs etc. don't require such per time step iterations to attain convergence. So, I would like to know that why do they not require it?

This question came to my mind when I was coding the Sod's Shock Tube Problem in Matlab and simultaneously in Fluent.

[FMDenaro]

I suggest starting to learn explicit and implicit time integration for simple one-equation model. Then, you can understand their application in the case of a system of coupled equation. Use a good textbook of CFD or numerical analysis.

[mome]

Hi, are you maybe simply confused about explicit and implicit schemes? Maybe you can catch up on this by looking it up on google or your favourite CFD book
if a scheme is explicit, as FTCS or Lax-Friedrich, it can evaluate the next point only based on known values, so no iteration is required. if you're new to CFD, it is also helpful if you keep finite difference and finite volume schemes distinguished when comparing scheme properties if you want to avoid confusion (you listed a mix) have fun!

[mome]

oops too slow, sry

[Senbonzakura]

Thank You for the reply. Now, I do understand why this is happening.