DEVELOPMENT OF FIBRE LDA AND TWO-COMPONENT VELOCITY MEASUREMENTS IN BOUNDARY LAYER ON AN INCLINED HEATED PLATE.

The present paper deals with the development of miniaturized Argon-Ion two-color LDA optical probe that can be easily traversed in any attitude. The miniaturization is achieved by employing step index single-mode fibres to transmit beams from a laser source to the probe head. This fibre LDA is operated in a two-color four-beam differential mode with frequency shifters (Bragg cells) to sense a backward flow and two-component velocities. An application of the fibre LDA is adopted to a boundary layer flow over an isothermally heated plate which is installed in a inclined wind tunnel, where the laminar boundary layer transits to turbulence with an increase in wall temperature. The experimental results indicate the velocity distributions of two-components, their turbulence intensities, Reynolds shear stresses, and correlations between two-component velocity fluctuations.