Journal of Fluid Mechanics

The onset of cellular convection in a fluid layer with time-dependent density gradients

L. M.  Blair a1 and J. A.  Quinn a1
a1 Department of Chemistry and Chemical Engineering, University of Illinois, Urbana, Illinois

Article author query
blair lm   [Google Scholar] 
quinn ja   [Google Scholar] 


Onset times for convection induced by buoyancy forces have been measured. Results on three aqueous systems are summarized in terms of a critical value for a time-dependent Rayleigh number. Because of the presence of minute traces of unavoidable surface-active contaminants, a ‘free’ water surface behaved as if it were inflexible and laterally rigid so far as determining first convective motion was concerned. The form of the onset motion was observed with schlieren photography for both top and side view. The pattern at onset was frequently in the form of plunging rings. Surface effects were demonstrated with an organic liquid layer in which onset times were measured for convection driven by surface tension gradients as well as by buoyancy forces. The data are compared with some recent predictions of linear stability analyses.

(Published Online March 29 2006)
(Received July 11 1968)