Instabilities of convection rolls in a high Prandtl number fluid

• DOI: 10.1017/s0022112071001071
• Publication Date: 2006-03-29T05:41:58Z
• Authors: F. H. Busse; J. A. Whitehead
• Keywords: 0103 physical sciences; 01 natural sciences

An experiment on the stability of convection rolls with varying wave-number is described in extension of the earlier work by Chen & Whitehead (1968). The results agree with the theoretical predictions by Busse (1967a) and show two distinct types of instability in the form of non-oscillatory disturbances. The ‘zigzag instability’ corresponds to a bending of the original rolls; in the ‘cross-roll instability’ rolls emerge at right angles to the original rolls. At Rayleigh numbers above 23,000 rolls are unstable for all wave-numbers and are replaced by a three-dimensional form of stationary convection for which the name ‘bimodal convection’ is proposed.