Effect of Doppler ambiguity on the measurement of turbulence spectra by laser Doppler velocimeter

For the measurement of turbulent flows, the effect of finite transit times of scatterers to cross the scattering region in a laser Doppler velocimeter is discussed. The result shows that in the measurement of the velocity spectrum, it is equivalent to a white spectrum noise with an amplitude inversely proportional to the average transit time. Theoretically, the noise becomes negligibly small when the wavelength of the laser light becomes very short.