BOUNDARY LAYER STABILITY AND TRANSITION.
BOUNDARY LAYER STABILITY AND TRANSITION.

Author:

Publisher:

Published: 1969

Total Pages: 45

ISBN-13:

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A review is given of boundary layer stability and transition. The normal modes procedures as they apply to boundary layers are briefly reviewed and the mechanism of instability is discussed. It is shown how normal modes results may be used to give guidance regarding the factors affecting transition. Some remarks are made about the prediction of transition and about the fixing of transition. It is concluded that the process of transition from laminar to turbulent flow remains unsolved. However, significant inroads into inroads into the understanding of transition are now possible because of our ability to do sophisticated theoretical and experimental studies of the stability of laminar boundary layers.

Review of the Effect of Distributed Surface Roughness on Boundary-layer Transition
Review of the Effect of Distributed Surface Roughness on Boundary-layer Transition

Author: A. L. Braslow

Publisher:

Published: 1960

Total Pages: 13

ISBN-13:

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A discussion is presented on the transition phenomena associated with distributed roughness, a correlation of three-dimensional roughness effects at both subsonic and supersonic speeds, and the effect of laminar boundary-layer stability as influenced by heat transfer, pressure gradients, and boundary-layer control on the sensitivity of laminar flow to distributed roughness. Results indicate that the transition-triggering mechanism of three-dimensionaltype surface roughness appears to be the same at supersonic and subsonic speeds. In either case, a Reynolds number based on the height of the roughness and the local flow conditions at the top of the roughness can be used to predict with reasonable accuracy the height of threedimensional roughness required to cause premature transition. Neither the three-dimensional roughness Reynolds number nor the lateral spread of turbulence behind the roughness is changed to any important extent by increasing the laminar boundary-layer stability to theoretically small disturbances. Therefore, for a given stream Mach number and Reynolds number, surface cooling, boundary-layer suction, or a favorable pressure gradient will, in the presence of three-dimensional roughness, promote rather than delay transition. (Author).