Studies of Transitional Flow,Unsteady Separation Phenomena and Particle Induced Augmentation Heating on Ablated Nose Tips.

摘要

This report describes the results of two distinct studies of the aerodynamic heating of nose tips. In Part 1 the development of laminar, transitional and turbulent boundary layers over ablated nose shapes at Mach numbers from 8 to 13 for Reynolds numbers up to 80x10 to the 6th power based on model diameter were studied experimentally. Two groups of models were employed in this study; blunt elliptic, blunt biconic and triconic models were used in the first phase of this investigation where the greatest emphasis was placed on examining the length and structure of the transition region and the parameters which influence it. The second phase of this study was devoted to examining the flow over 'highly ablated' nose shapes, over which flow separation and gross flow instabilities occurred. The influence of nose tip configuration, roughness and model incidence, as well as the Mach number and Reynolds number of the free stream on the occurrence and structure of large scale periodic instabilities was studied. These studies demonstrated the strong effect of pressure gradient and roughness on the length and characteristics of the transition region. In turn these parameters, along with nose tip geometry, strongly influence the occurrence of flow instabilities over highly-indented nose shapes. In Part 2 of this investigation, the generation of disturbances in the stagnation region of the flow as a particle, (which comes from the model surface), interacts with the bow shock was studied in detail.