Photogrammetry Measurements of Blunt Body Dynamics in a Supersonic Wind Tunnel

Abstract This paper presents free-oscillation experiments of a blunt body conducted in a high-speed wind tunnel, with the model motion measured using photogrammetry. A faceted blunt model, mounted on a spherical air bearing, is free to rotate in roll, pitch, and yaw in response to the freestream flow ( M = 2). Four synchronised high-speed cameras capture the model from multiple angles, and the unique coded targets printed on the model’s surface are reconstructed as points in 3D space, achieving accuracy within $$\text {1}^{\circ }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mtext>1</mml:mtext> <mml:mo>∘</mml:mo> </mml:msup> </mml:math> for both static and dynamic measurements. The Kabsch algorithm is used to find the optimal rotation between two point clouds, hence allowing reconstruction of the angular motion over the entire run. The method shows promise for free-oscillation tests in high-speed ground facilities, offering advantages over ballistic range and free-flight tests such as a constant freestream velocity and hundreds of oscillation cycles. This capability enables the observation of dynamic instabilities that develop over extended timescales, thus revealing a precessional instability previously reported only for slender bodies at hypersonic Mach numbers.