Journal of Fluid Mechanics

Double-diffusive instability in an inclined fluid layer. Part 1. Experimental investigation

R. C.  Paliwal a1p1 and C. F.  Chen a1
a1 Department of Mechanical, Industrial and Aerospace Engineering, Rutgers University, New Brunswick, N.J. 08903

Article author query
paliwal rc   [Google Scholar] 
chen cf   [Google Scholar] 


The stability boundary of a density-stratified fluid contained in an inclined slot subjected to a lateral temperature gradient was determined experimentally. The initial stratification due to salt was stable and linear in the vertical direction. Experiments were conducted in a 1·0 × 11.1 × 25·7 cm slot with the inclination angle θ from the vertical varying from −75° to + 75°. A positive angle denotes heating from the lower wall while a negative angle denotes heating from the upper wall. The temperature difference across the slot was increased slowly until the onset of instability was observed by means of a shadowgraph. The critical thermal Rayleigh number was found to be non-symmetrical with respect to θ = 0°, with heating of the upper wall less stable than heating of the lower wall. This is because there is a larger vertical solute gradient in the steady-state regime prior to the onset of instabilities when the lower wall is heated. The secondary flow consisting of horizontal convecting layers was very stable θ < 0° cases because of the stabilizing temperature effect. The motion of the layers when θ > 0° was quite vigorous. At θ = +75°, the secondary flow became unstable in a rather dramatic manner not observed heretofore.

(Published Online April 19 2006)
(Received May 21 1979)
(Revised October 18 1979)

p1 Present address: Electronic Associates, Inc., West Long Branch, N.J. 07764.