Investigation of Boundary-Layer Transition on Smooth Hemispherical Bodies
NAVAL AIR WARFARE CENTER WEAPONS DIV CHINA LAKE CA
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The main goal of this project was to determine if known correlations can be used to predict the occurrence and location of boundary-layer transition on smooth hemispherical surfaces with very small roughness heights 25 -tin . A number of empirical correlations were evaluated against experimental data, however, no universal correlation was found that could acceptably describe the observed transition events during the flight tests analyzed. Only a sparse set of data was available for deriving and assessing the various correlations correlations derived from a larger set of data may be better suited for predicting transition. The correlations examined implement many of the parameters traditionally used such as geometry, surface roughness, edge Mach number, boundary-layer momentum thickness, and Reynolds number, but are based on an incomplete understanding of the relevant physics. Because these correlations do not account for the physical processes driving transition, they cannot be used to accurately predict the occurrence or location of transition from laminar to turbulent flow. In addition, two of the flight tests considered showed periods of higher heating inconsistent with predictions based on laminar theory that were not investigated by the original authors. Transition during these periods appears to be forced by transitory events related to the operation of the sounding rockets, such as motor burnout transients and other unidentified mechanisms. In order to be able to better predict transition, it will be necessary to obtain a clear understanding of the physical processes that cause transition.
- Fluid Mechanics