Basic LDA Principles

Laser Doppler anemometry utilizes the Doppler effect to measure instantaneous particle velocities [5, 97, 213]. The laser Doppler technique generally uses a collimated, monochromatic and coherent laser as light source. Lasers with wavelengths A 

Relation (13.1) shows that in principle the particle velocity can be determined from measurements of the Doppler shift Af. For this reason the system interpretation is named the Doppler-shift method. However, in practice this frequency shift can only be measured directly for very high particle velocities. For this reason the Doppler-shift interpretation is not commonly used in practice. 

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