[saisanthoshm88]

Could someone please let me know, why natural convection is inherently transient

[evcelica]

The turbulence intensity of natural convection is usually very high. There is a lot more fluid motion due to just turbulence than the mean flow velocity. think of smoke coming off a cigarette, It does not have a steady state solution. But a steady state model should give you a lot of information on the average flow (depending) It just will not converge the residuals since the flow keeps changing.