Three-Dimensional Hypersonic Boundary Layer Stability and Transition


Book Description

The stability and transition of three-dimensional boundary layers was studied. In the first phase of the investigation, arrays of hot film probes were used to measure the three-dimensional structure of instability waves on an axisymmetric cone at Mach 8. In the second phase, linear stability theory was used to design a cone with an elliptic cross section, which was also tested at Mach 8. Results show that disturbances on the axisymmetric cone travel in wave packets with predominantly zero wave angle. On the elliptic cone, only weak evidence for stationary waves was found. The predominant waves were traveling waves at about 12 kHz. Additional waves, probably second mode, occurred near 80 kHz.










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.







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.




Three-dimensional Laminar Boundary-layer Analysis of Upwash Patterns and Entrained Vortex Formation on Sharp Cones at Angle of Attack


Book Description

Application of three-dimensional inviscid and viscous (laminar boundary layer) analyses for cold wall hypersonic flows over sharp cones at incidence is presented relative to experimental data, showing surface upwash angles and entrained vortex formation leading to crossflow-induced boundary-layer transition. Three-dimensional neutral inviscid stability theory for stationary disturbances is used to calculate the angular orientation of the entrained vortices in the boundary layer while a maximum crossflow Reynolds number concept is applied for correlation of the onset to vortex formation due to crossflow instability.










Instability, Transition, and Turbulence


Book Description

This volume contains the proceedings of the Workshop on In stability, Transition and Turbulence, sponsored by the Institute for Computer Applications in Science and Engineering (ICASE) and the NASA Langley Research Center (LaRC), during July 8 to August 2, 1991. This is the second workshop in the series on the subject. The first was held in 1989, and its proceedings were published by Springer-Verlag under the title "Instability and Transition" edited by M. Y. Hussaini and R. G. Voigt. The objectives of these work shops are to i) expose the academic community to current technologically im portant issues of transition and turbulence in shear flows over the entire speed range, ii) acquaint the academic community with the unique combination of theoretical, computational and experimental capabilities at LaRC and foster interaction with these capabilities, and iii) accelerate progress in elucidating the fundamental phenomena of transition and turbulence, leading to improved transition and turbulence modeling in design methodologies. The research areas covered in these proceedings include receptiv ity and roughness, nonlinear theories of transition, numerical simu lation of spatially evolving flows, modelling of transitional and fully turbulent flows as well as some experiments on instability and tran sition. In addition a one-day mini-symposium was held to discuss 1 recent and planned experiments on turbulent flow over a backward facing step.