Ultrasonic Lift Measurement Technique for Flow-Induced Structural Vibrations
Publication: Journal of Aerospace Engineering
Volume 18, Issue 2
Abstract
Deficiencies exist in our current ability to measure lift forces in wind-tunnel experiments on vibrating structures in a fluid flow. The ultrasonic lift measurement (ULM) technique has been previously developed to measure time-averaged fluid circulation and lift on stationary structures. The ULM technique is based on measuring transit times of acoustic pulses along paths enclosing the structure. A quasi-steady method based on the Kutta–Joukowski theorem has been used in the past to convert fluid circulation to lift values in ULM studies. In this paper, the largely unstudied extension of the ULM technique to measure unsteady lift forces in flows involving structural vibration is considered. Analytic methods are developed that can be used to properly convert the instantaneous circulation measurements (attainable from ULM experiments) to lift values. These unsteady methods are validated by using numerical simulations of flows over flat plates undergoing oscillating motion. It is shown that the addition of unsteady terms provides a method with improved accuracy over the previous quasi-steady assumption. The methods are also applied to ULM data from an oscillating airfoil experiment in a preliminary study.
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Acknowledgments
This work was partially supported by the Office of Naval Research. We thank Prof. H. Johari for useful discussions regarding the ULM technique, Prof. A. N. Alexandrou for his guidance on the finite element simulations, and G. Balasubramanian for his help with the numerical grids.
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Information & Authors
Information
Published In
Journal of Aerospace Engineering
Volume 18 • Issue 2 • April 2005
Pages: 111 - 119
Copyright
© 2005 ASCE.
History
Received: Mar 7, 2003
Accepted: Apr 27, 2004
Published online: Apr 1, 2005
Published in print: Apr 2005
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