Krishnamurti 



move more rapidly to transport this Increased heat flux. If the fluid 

 must move faster, then the cells must be larger In order to allow 

 the hot rising fluid to be In the vicinity of the cold upper boundary for 

 a sufficiently long time to lose its heat before sinking and repeating 

 the process. Although there are many ways in which the fluid could 

 have transferred the increased heat flux, moving more rapidly with 

 increased cell size Is one of them. Of course. If the cells become 

 very large, the viscous dissipation of energy near the horizontal 

 boundaries would slow down the flow and defeat its own purpose. 

 This will be discussed later. It is seen in Fig. 4 that, when the cell 

 size is allowed to evolve freely (without being forced as in the ex- 

 periments of Chen and Whitehead [ 1968]), approximately one-half 

 of Busse's stability diagram Is filled with observations, but the 

 domain p > p^ is conspicuously bare. 



2x10* 



1x10* 



i? t 



5x10' 



3x10^ 



SxlC 



Fig. 4. The observed cell size plotted on Busse's stability diagram 

 for two-dimensional rolls 



296 



