Measurement of skin friction at hypersonic speeds using fiber-optic sensors

Abstract

This paper describes the efforts that have been made in the development of various measurement systems based on fiber-optic sensors and associated signal processors at the Department of Aerospace Engineering, Indian Institute of Science during the last 3-4 years. Fiber-optic sensors have been developed in USA since 1990, for variety of applications in experimental stress analysis, skin friction measurement in fluid flows, smart structures, smart materials, sensing of acoustic emission and more recently in the development of compact devices for measurement of displacement, stress/strain, pressure, temperature, acceleration etc. Our group at IISc has been playing a lead role in the use of these fiber-optic sensors for successful measurement of aerodynamic loads in wind tunnels and the first ever six-component wind tunnel strain gauge balance in the world based on fiber optic sensors was built at the Indian Institute of Science in the year 1999. We report here the results of our efforts in the development of a skin friction measurement system for both low speeds as well as for high Mach numbers. Two different techniques have been employed to capture the skin friction loads viz..Fiber optic displacement sensors as well as Extrinsic Fabry - Perot Interferometer type strain gauge sensors.