Problems of theory and practical use of a laser doppler velocimeter in the investigation of turbulent flows

At present great attention is being devoted to the development of laser Doppler velocimeters (LDV) for experimental investigation of turbulent flows. The main types of optical schemes of LDV are discussed in this article. Formulas for the output signal of the photoreceiver and the results of spectral analysis of this signal with the statistics of the scattering centers taken into consideration are presented. The uncertainty relation for the spatial resolution and the width of the Doppler spectrum is obtained. The optical scheme of a three-component velocimeter and the block diagram of its electronic part are given. The potentialities of the meter are demonstrated using, as an example, flow past a cylinder.