Natural Convection Flow, Instability, and Transition

Abstract

In any estimation of transport rates in a convection process one must be concerned whether the flow is laminar or turbulent since the transport effectiveness is very different for these two flow regimes. The increasingly active research in natural convection processes generally has included, in the past few years, intensive study of how and when laminar natural convection flows, over surfaces, become turbulent. The following presentation summarizes what is known at this time concerning the total process. Initially unstable laminar flows amplify disturbances which eventually convert the flow to turbulence. The question of initial instability of laminar flow is considered, from theory and from experimental evidence. Calculations and observations of disturbance amplification are summarized. Experimental evidence concerning transition is discussed. Finally, based on the evidence of date, conjectures are made concerning additional aspects of the overall process. A number of appropriate unanswered questions are indicated.