Tripping of a Hypersonic Low-Reynolds-Number Boundary Layer
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2016 by the American Institute of Aeronautics and Astronautics, Inc. An array of NASA-designed diamond-shaped trips was employed to induce transition of a low-Reynolds-number (Re = 3600) Mach 5.65 laminar boundary layer. The purpose was to quantify the flow structure of a low-Reynoldsnumber turbulent boundary layer that was accessible to high-fidelity numerical simulation. The transition process and subsequent turbulent boundary layer were experimentally examined using hot-wire anemometry, pitot pressure probes, schlieren photography, and surface oilflow visualization. Downstream of the trips, peak disturbances near the boundary-layer edge were observed to grow in amplitude in the axial direction. By the aft measurement location (x/0 = 78), the energy was distributed across the boundary layer, indicating breakdown to turbulence. A spectral peak near 58 kHz was observed in the tripped flows at all measurement locations, which indicated the presence of KelvinCHelmholtz instabilities. Compressibility scaling of the velocity was found to collapse the sub-and log-layer region data with expected theory. When the turbulent boundary-layer power spectra were analyzed, the decay was found to follow the Kolmogorov-5/3 power law. Conversely, it was expected that the turbulence production and viscous dissipation balance was not fully established.