Instabilities and Vovtiaes Between Two Rotating Spheres 



that in the field between the two boundary layers of the rotating and 

 the fixed sphere -- according to the large gap --a flow is established 

 that moves with a constant but smaller angular velocity than the inner 

 rotating sphere. Obviously this type of motion prevents or at least 

 delays the development of the Taylor vortices. A similar pattern is 

 known to exist also in the gap between two discs [ 8] with one of them 

 rotating. 



II. This regime is characterized by a flow with vortices that 

 begin at the poles (Fig. 9). The axes of these vortices are inclined 



Fig. 9 Motion of Mode II. s = 1 2. 15 mm, Re = 8, 300 , 

 Ta = 630 



slightly to the streamlines close to the fixed sphere. With increasing 

 Reynolds number these vortices advance around the poles to the 

 equator. The axes become more and more wavy and finally the flow 

 turns turbulent. The physical explanation of these vortices is by no 

 means evident. We have the conjecture that we have here a situation 

 analogous to the occurrences close to a free rotating sphere [ 9] or 

 disc [ 10] . Very often these vortices are called Stuart vortices, 

 Contrarily to the familiar pattern of vortices, rotating with alternating 

 direction the Stuart vortices rotate all in the same direction, 



III. Two Taylor vertices develop symmetrical to the equator. 

 Outside the vortex zone we have mode I flow. Surprisingly at the 

 equator -- where the centrifugal force has its maximum -- the flow 



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