ABSTRACT
Flow velocity and its nondimensional form known as the Mach number are some of the most important parameters in fluid flow analysis. Some of the popularly used techniques are velocity measurement through pressure measurements, through optical properties like Doppler shift using laser Doppler anemometer, through measurement of the vortex shedding frequency, and through the heat transfer principle; using hot-wire anemometer. The principle underlying laser Doppler anemometer is that a moving particle illuminated by a light beam scatters light at a frequency different from that of the original incident beam. Although a number of configurations have been used for laser Doppler anemometer, the basic system can be broadly classified into two major categories, namely the reference beam system and the fringe system. In a reference beam system the scattered beam of light is optically mixed with the original beam and the difference is obtained as the Doppler shift in frequency.
