Instability and transition on a von Karman ogive in a Mach-6 quiet tunnel
Abstract
A von Karman ogive model was tested in the Boeing/AFOSR Mach-6 Quiet Tunnel (BAM6QT). This geometry consists of a hemispherical nosetip, followed by a von Karman ogive, with a cylindrical aft-body. Nosetip roughness was a concern for this design, as well as a possible step at the nosetip-body joint. Therefore, several roughness configurations were tested on the model. With a 3-in. base-diameter model at 0° angle of attack, there was a region of higher heating near the aft end of the model in the smooth-nose configuration, which could be an indication of transition. Additionally, the bow shock from the blunt nosetip reflected from the wind tunnel walls and impinged on the model. A 2-D roughness strip and a distributed roughness on the nosetip did not significantly affect the flow, but an isolated roughness element produced a wedge of higher heating behind the element. When the 3-in. model was tested at angle of attack, it was unclear if the tunnel started. The tunnel did start with the 3-in. model at 0° angle of attack and with a 2-in. model at 0° angle of attack and 2° angle of attack. Most of the testing was performed with the 2-in. base-diameter model at 2° angle of attack. In the smooth configuration, there was a region of higher heating at the aft end of the model on the leeward side, indicating transition. Forward- and aft-facing steps had little effect on the transition location. However, a distributed roughness appeared to move the transition location forward on the model, and an isolated roughness element again created a wedge of higher heating. An attempt was made to measure instability waves on the model. While no second-mode waves were detected, there were indications of first-mode waves.
Degree
M.S.A.A.
Advisors
Schneider, Purdue University.
Subject Area
Aerospace engineering
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