I am trying to simulate thermally driven square cavity with turbulence model k-kL to study natural convection. But i am not sure about the initialization as here velocity is zero initially. Please help me?

Quick answer: With most turbulence models, you should at least initialize the turbulence fields with very small values, even if the velocity is zero initially.

At the very least, there is always the explanation that turbulence always exists, it's just we can't measure it or we can ignore it, because it exists at the molecular scale...

Thanks. I will try to simulate by assuming small values at initialization. Let's see if i'm able to get the correct result.