The Effect of Pressure Gradients on Transition Zone Length in Hypersonic Boundary Layers


Book Description

Boundary layer transition was measured in zero, favorable, and adverse pressure gradients at Mach 8 using heat transfer. Models consisted of 7 degrees half angle forecones 0.4826 m long, followed by flared or ogive aft bodies 0.5334 m long. The flares and ogives produced constant pressure gradients. For the cases examined, favorable pressure gradients delay transition and adverse pressure gradients promote transition, but transition zone lengths are shorter in favorable pressure gradient. Results of the effect of adverse pressure gradient on transition zone lengths were inconclusive.




The Effect of Pressure Gradients on Transition Zone Length in Hypersonic Boundary Layers


Book Description

Boundary layer transition was measured in zero, favorable, and adverse pressure gradients at Mach 8 using heat transfer. Models consisted of 7 degrees half angle forecones 0.4826 m long, followed by flared or ogive aft bodies 0.5334 m long. The flares and ogives produced constant pressure gradients. For the cases examined, favorable pressure gradients delay transition and adverse pressure gradients promote transition, but transition zone lengths are shorter in favorable pressure gradient. Results of the effect of adverse pressure gradient on transition zone lengths were inconclusive.




Comments on Hypersonic Boundary-layer Transition


Book Description

This is a survey paper on the subject of hypersonic boundary-layer transition. Part 1 discusses boundary-layer stability theory, hypersonic boundary-layer stability experiments, and a comparison between theory and experiment. Part 2 contains comments on how many configuration and flow parameters influence transition. Part 3 discusses some additional general aspects of transition. Part 4 discusses problems of predicting transition and comments on three prediction methods. Part 5 contains some general guidelines for prediction methodology. Keywords: Boundary layer transition, Boundary layer stability, Hypersonic boundary layers.







Factors Affecting Transition at Supersonic Speeds


Book Description

This paper surveys the available material and summarizes what is known to date about boundary-layer transition at supersonic speeds. Variables studied include Mach number, Reynolds number, pressure gradients, heat transfer, surface roughness, and angle of attack. The discussion is limited to bodies of revolution because similar reliable data for wings is lacking.




Boundary Layer Transition at Supersonic Speeds


Book Description

Experiments carried out in the 12-inch supersonic wind tunnel to investigate the effect of three dimensional roughness elements (spheres) on boundary-layer transition on a 10-degree (apex angle) cone without heat transfer are described. The local Mach number for these tests was 2.71. The data show clearly that the minimum (effective) size of trip required to bring transition to its lowest Reynolds number varies power of the distance from the apex of the cone to the trip. Use of available data at other Mach numbers indicates that the Mach number influence for effective tripping is taken into account by a simple expression. Some remarks concerning the roughness variation for transition on a blunt body are made. Finally, a general criterion is introduced which gives insight to the transition phenomenon and anticipates effects of external and internal disturbances, Mach number transfer.







An Experimental and Analytical Investigation of Hypersonic Inlet Boundary Layers: Data reduction program and tabulated experimental data


Book Description

Detailed boundary layer surveys were made on four axisymmetric compression surface models simulating typical hypersonic inlet compression surfaces at free stream Mach numbers ranging from 4 to 8. The four models were designed to provide isentropic compression at design Mach numbers of 5, 6, 8 and 10. The Mach 8 design model had provisions for wall cooling. Quantitative heat transfer measurements were made on the Mach 8 model at free stream Mach numbers of 5, 6, and 8. Two existing turbulent boundary layer theories were modified to account for the various phenomena found to be of importance in hypersonic boundary layers. Theoretical results from these methods were correlated with the experimental data. A significant observation of the present program is the powerful favorable effect of centrifugal force phenomena on boundary layer development in continuous adverse pressure gradients. It was found that these effects become more pronounced with increasing Mach number and reductions in free stream Reynolds number.







Boundary-layer Transition Study of Several Pointed Bodies of Revolution at Supersonic Speeds


Book Description

Boundary-layer transition by the sublimation and impact-pressure techniques and force tests have been performed on three Haack-Adams bodies of revolution of fineness ratios 7, 10, and 13 at zero angle of attack for free-stream Mach numbers of 2.00, 2.75, and 4.63 and a range of Reynolds numbers based on model length of 6 to 15 X 10(to the 6 power) with and without a roughness strip. The grit method of inducing turbulence was found to provide for a nearly complete turbulent flow over the models at the lower Mach numbers and higher Reynolds numbers considered in this study while the amount of trip drag was less than 8 percent of the model drag with transition fixed. A method of interpreting sublimation data was discussed and used and the results compared well with the impact-pressure results.