Flow diagnostics using fibre optics

Abstract. Research in the area of flow diagnostics using fibre-optics started in our laboratory in early 1998. The first-ever multi-component wind tunnel balance in the world, working with fibre-optic sensors was built and demonstrated in 1999. Since then, several new applications of the technique in the area of fluid dynamic load measurements have been tried successfully. Very recently, fibre-optic sensors have been effectively used for underwater applications, where conventional mea-surements are relatively very difficult. Since, different physical perturbations affect optical power flowing in a fibre in different ways, unique signatures can be obtained which allow absolute or relative measurement of the incident disturbances. Immu-nity to electromagnetic or radio frequency interference, high temperature capability, low fatigue, high sensitivity, small size, good corrosion resistance and the capa-bility to embed sensors within the model surface are some of the very attractive features of fibre-optic based instrumentation systems. In this paper, we describe the results of experiments of aerodynamic load measurements at hypersonic speeds (Mach 8·35 and 7·0) and studies carried out recently in a water tunnel over a lifting hypersonic vehicle with a 2-component fibre-optic strain-gauge balance