An Evaluation of Four Experimental Methods for Measuring Mean Properties of a Supersonic Turbulent Boundary Layer
Abstract
Surveys were made through a turbulent boundary layer on a flat plate by means of a pitot probe, an X-ray densitometer, and hot-wire and cold-wire probes. Results from these surveys were analyzed to determine (a) the reliability of the basic data and hence the methods by which they were obtained, and (b) how well the actual distributions of properties in the boundary layer compare with those commonly assumed in semiempirical and theoretical analyses. All surveys were made at the same longitudinal station on the flat plate. The tests were conducted in an 8- by 8-inch supersonic nozzle. The free-stream Mach number was 3.03 and the Reynolds number was approximately 210,000 based on boundary-layer thickness. Analysis of the data revealed the following points. The values of mean pitot pressure, mean density, and mean total temperature obtained from the pitot probe, X-ray densitometer, and cold-wire probe combined to produce consistent distributions of mean Mach number, mean total temperature, and mean mass flow throughout the boundary layer. The hot-wire probe, however, indicated values of mean mass flow over the outer portion of the boundary layer that were higher than the values obtained from the pitot, X-ray, and cold-wire surveys. This result was confirmed in an independent test performed in the Ames 1- by 3-foot supersonic wind tunnel. It is suggested, therefore, that caution should be used in interpreting hot-wire data to represent mean mass flows in turbulent supersonic boundary layers. Except for the region very near the plate surface, the assumption of constant total temperature through the boundary layer yielded negligible errors in velocity distribution and displacement and momentum thicknesses. The one-sixth power law was found to agree with the experimental velocity distribution within +/- 2 percent.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1956
- Accession Number
- ADA380503
Entities
People
- George J. Nothwang
Organizations
- National Aeronautics and Space Administration