Internally mounted laser-Doppler-anemometry system for boundary layer measurement

摘要

This paper describes a fibre-optic laser-Doppler-anemometry (LDA) system for measuring the boundary layer around a cylinder in a water tank. The laser head is located inside the cylinder, and the beams are focused in the flow near the surface of the cylinder through a transparent window. The main difficulties were in minimising the deformation of the interference pattern of the measuring control volume in order to obtain a sufficient signal in back-scattering operation.