Krishnamurti 



II. TRANSITION TO TURBULENT CONVECTION IN A NON- 

 ROTATING LAYER OF FLUID 



Unlike the fast transition to turbulence in plane parallel shear 

 flows, the horizontal convecting layer undergoes a number of discrete 

 transitions, remaining in each regime for a finite range of Rayleigh 

 number. The transition to turbulent convection appears to result in 

 the following manner: at sufficiently low values of the Rayleigh 

 number the fluid system is stable to all small disturbances. As the 

 value of R is Increased the system becomes unstable to one kind of 

 disturbance. As R is increased still further the fluid becomes un- 

 stable to more kinds of disturbances. At sufficiently large Rayleigh 

 numbers the flow is unstable to so many kinds of disturbances, each 

 occurring with uncontrolled phase, that the flow may be called tur- 

 bulent. Before discussing the first three of these transitions, the 

 experimental apparatus will be described. 



Apparatus 



One of the possible designs of experimental apparatus is 

 shown in Fig. 1. The fluid layer occupies a region 51 by 49 cm, 

 with a depth that can be chosen (usually between 1/2 and 5 cm). 



C0NST4NT 

 TEMPERATURE 

 CiRCULftTING 

 COOLER 



o 



o 

 w 



oooooooo 

 o o o o o o o 



METMftCRYLflTE 



Fig. 1 . Apparatus 



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