Experiments in Fluids

, 59:25 | Cite as

Inverse measurement of wall pressure field in flexible-wall wind tunnels using global wall deformation data

  • Kenneth Brown
  • Julian Brown
  • Mayuresh Patil
  • William Devenport
Research Article
  • 209 Downloads

Abstract

The Kevlar-wall anechoic wind tunnel offers great value to the aeroacoustics research community, affording the capability to make simultaneous aeroacoustic and aerodynamic measurements. While the aeroacoustic potential of the Kevlar-wall test section is already being leveraged, the aerodynamic capability of these test sections is still to be fully realized. The flexibility of the Kevlar walls suggests the possibility that the internal test section flow may be characterized by precisely measuring small deflections of the flexible walls. Treating the Kevlar fabric walls as tensioned membranes with known pre-tension and material properties, an inverse stress problem arises where the pressure distribution over the wall is sought as a function of the measured wall deflection. Experimental wall deformations produced by the wind loading of an airfoil model are measured using digital image correlation and subsequently projected onto polynomial basis functions which have been formulated to mitigate the impact of measurement noise based on a finite-element study. Inserting analytic derivatives of the basis functions into the equilibrium relations for a membrane, full-field pressure distributions across the Kevlar walls are computed. These inversely calculated pressures, after being validated against an independent measurement technique, can then be integrated along the length of the test section to give the sectional lift of the airfoil. Notably, these first-time results are achieved with a non-contact technique and in an anechoic environment.

Notes

Acknowledgements

Funding for this work was provided by the Stability Wind Tunnel at Virginia Tech. The authors would like to thank Dr. Rakesh Kapania and Dr. Robert Canfield for their valuable insights on inverse techniques and membrane mechanics. Dr. Aurelien Borgoltz also contributed meaningful knowledge both to the content in this article and to the preceding development of Kevlar-wall measurement techniques. Bill Oetjens and Tim Meyers of the Stability Wind Tunnel assisted greatly with the experiment. In addition, Julio Estrella and Stephanie Hoang are gratefully acknowledged for their measurements of the Kevlar pre-tension.

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of Aerospace and Ocean EngineeringVirginia TechBlacksburgUSA
  2. 2.Department of Mechanical EngineeringVirginia TechBlacksburgUSA

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