Threedimensional Laser-Doppler AnemometryCopyright: EBC
To use Laser Doppler Anemometry (LDA) the air has to be seeded with tracer particles. Two laser beams (for each velocity component) are crossing and creating a small measurement volume. If the laser light is reflected inside this volume due to the moving particles, there will be a Doppler shift of the incident and scattered laser frequency and this shift is proportional to the particle velocity. With LDA only small volumes (compared to PIV) can be measured to a given time but the measurement is very exact. The application of LDA is similar to PIV.