Dynamic Force Measurement in Hypersonic Wind Tunnels

Thumbnail Image
Publication or External Link
Draper III, John Willis
Lee, Sung W
In this dissertation, dynamic force measurement methodologies are developed and implemented for use in hypersonic wind tunnel testing. The chief application is implementation into Arnold Engineering Development Complex's Hypervelocity Wind Tunnel No. 9. The Sum of Weighted Accelerations Technique, Time Domain Deconvolution Method, and Frequency Domain Inverse Method are of particular interest for this study due to their implementation feasibility within Tunnel 9. The formulation of each "conventional" method is presented in its most basic or commonly used form. Then several modifications are made to improve the results of the various methods. Much of this work focuses on the specific alterations performed on each method and the consequences of each change. To improve the Sum of Weighted Accelerations Technique, modal separation and a damping matrix are added to the formulation. This allows for higher frequency accuracy and successful reconstructions on highly damped setups. A novel Time Domain Deconvolution Method is formulated in this dissertation which exhibits several advantages over the typical time domain approaches. Examples include elimination of inversion regularization, smooth reconstructions, and improved computational efficiency via response segmentation. The Frequency Domain Inverse Method was reformulated to solve directly for the frequency response function. This direct solution also allows for the use of multiple calibration tests during solution which improves accuracy. Each alteration is validated on numerical, bench top, and wind tunnel systems to provide a full theory to implementation understanding. Linked spring-mass-damper models are used for all of the numerical investigations with additive Gaussian noise and are used to draw early conclusions about each method and alteration. Bench top studies are performed on three separate support structures to build confidence in the methods on a more complex, experimental system. Finally, data obtained by tests performed in a transonic wind tunnel are used to demonstrate the capabilities and highlight some of the advantages of each method.