A Note on the Effect of Short and Long Laminar Separation Bubbles on Desinent Cavitation

1981 ◽  
Vol 103 (1) ◽  
pp. 28-32 ◽  
Author(s):  
V. H. Arakeri ◽  
J. A. Carroll ◽  
J. W. Holl
Keyword(s):  
Flow Visualization ◽  
Viscous Flow ◽  
Critical Velocity ◽  
Film Flow ◽  
Separation Bubble ◽  
Sudden Change ◽  
Cavitation Number ◽  
The Body ◽  
Laminar Separation Bubble ◽  
Laminar Separation

Earlier desinent cavitation studies on a 1/8 caliber ogive by one of the authors (J. W. H.) showed a sudden change in the magnitude of the desinent cavitation number at a critical velocity. In the present work it is shown by means of oil-film flow visualization that below the critical velocity a long laminar separation bubble exists whereas above the critical velocity the laminar separation bubble is short. Thus the desinent cavitation characteristics of a 1/8 caliber ogive are governed by the nature of the viscous flow around the body.

The Initiation Of Gaseous Microbubble Growth In Laminar Separation Bubbles

1981 ◽  
Vol 103 (4) ◽  
pp. 543-549 ◽  
Author(s):  
B. R. Parkin
Keyword(s):  
Cavitation Bubble ◽  
Separation Zone ◽  
Separation Bubble ◽  
Practical Interest ◽  
The Body ◽  
Laminar Separation Bubble ◽  
Flow Conditions ◽  
Laminar Separation ◽  
Cavitation Inception ◽  
Air Diffusion

Flow conditions surrounding bubble-ring cavitation inception on hemispherical headforms are analyzed with respect to the initiation of air diffusion into microbubbles as is observed to occur at fixed positions in the boundary layer. Fairly recent observations have shown this phenomenon to occur in the laminar separation bubble on the body. The analysis shows, in agreement with the body of experimental evidence now available, that gaseous growth must be preceded by a period of vaporous growth starting in regions of low pressure upstream of the laminar separation bubble. It also appears that the most favorable condition for the initiation of gaseous growth should occur when a typical vapor bubble reaches its maximum radius as it enters the laminar separation bubble. The conditions for the initiation of subsequent gaseous growth, once the cavitation bubble is stabilized in the laminar separation zone, are more demanding. Nevertheless, it is found that the liquid in the water surrounding the bubble in the separation zone is definitely supersaturated for most flows of experimental or practical interest. Therefore, gaseous growth, as well as vaporous growth, is definitely to be associated with the onset of bubble-ring cavitation on both theoretical and experimental grounds.

Loss Production Mechanisms in a Laminar Separation Bubble

2012 ◽  
Vol 89 (4) ◽  
pp. 547-562 ◽  
Author(s):  
Daniele Simoni ◽  
Marina Ubaldi ◽  
Pietro Zunino
Keyword(s):  
Separation Bubble ◽  
Laminar Separation Bubble ◽  
Laminar Separation ◽  
Production Mechanisms
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