Criteria for Predicting the Transition to Turbulence in Natural Convection Along a Vertical Surface

This paper evaluates the existing criteria for predicting the transition to turbulence in natural convection adjacent to a vertical surface. We have conducted an experiment that establishes the point of transition in mercury by means of both hot-film anemometry and local heat transfer measurements. These results confirm the claim of Bejan and Lage that the Grashof number correlates transition data better than the Rayleigh number. We have also concluded that the laminar-turbulent transition in liquid metals as well as regular fluids occurs in the vicinity of Gr_x=10⁹. Furthermore, we show that the E parameter suggested by Gebhart and his co-workers for predicting the onset of transition, when appropriately modified, yields a criterion that depends on the Grashof number alone.