Observations of Turbulent-Burst Geometry and Growth in Supersonic Flow
Abstract
One step in the process of boundary-layer transition is the formation and spread of turbulent spots or bursts. A study of the shape, growth, and formation rate of turbulent bursts in supersonic boundary layers has been made using spark shadowgraphs of small gun-launched models in free flight through still air and through a countercurrent supersonic air stream. The shadowgraph data were obtained from a number of previous investigations which, collectively, represent a variety of model shapes, and a fairly wide range of Mach numbers, unit Reynolds numbers, surface roughnesses, and heat transfer rates. The model shapes include cones, ogive-cylinders, and hollow cylinders alined with the stream. The approximate ranges of the flow variables are as follows: free-stream Mach numbers from 2.7 to 10; unit Reynolds numbers from 1.6 million to 6.3 million per inch; surface roughness maximum peak-to-valley distance 10 micro inches to 2100 microinches; and ratio of wall temperature to free-stream temperature either 1.0 (still air) or 1.8 (countercurrent air stream). Three-dimensional burst geometry was determined for two typical turbulent bursts. From a comparison of burst plan forms and thickness profiles observed under different flow conditions, burst geometry was found to be insensitive to variation of Mach number, unit Reynolds number, and surface roughness. These variables, together with body shape, were found to have significant effects on the rate at which a burst is swept along the surface, its growth rate (relative to distance traveled), and the rate of burst formation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1958
- Accession Number
- ADA380488
Entities
People
- Carlton S. James
Organizations
- National Aeronautics and Space Administration