Influence of Refraction on the Applicability of the Zehnder-Mach Interferometer to Studies of Cooled Boundary Layers
Abstract
In order to determine the applicability of the Zehnder-Mach interferometer to two-dimensional cooled-boundary-layer studies, an analytical investigation was conducted. It was found that for low wall to free-stream temperature ratios, the effects of light refraction may cause considerable error in the boundary-layer density profiles calculated from interferogram measurements if these effects are not taken into account and that it is impossible to observe the boundary layer very close to the cooled wall. This report therefore contains a discussion of the magnitude of the refraction effects that may be expected and acts as a guide in the design of two-dimensional test sections for the study of cooled boundary layers by the interferometric method. Equations are derived and used to compute the trajectories of light rays through particular boundary layers as well as the approximate corrections that must be applied to the boundary-layer density values to take into account the effects of refraction. The computations were made for a range of conditions that is mainly of interest in turbine-blade cooling studies. Laminar and turbulent boundary layers that have a free-stream Mach number of 1.0, no pressure gradients in the flow direction, and wall to free-stream temperature ratios from approximately 0.33 to 0.9 were considered.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1951
- Accession Number
- ADA380446
Entities
People
- Martin R. Kinsler
Organizations
- National Aeronautics and Space Administration