PHASE-DOPPLER ANEMOMETRY WITH THE DUAL BURST TECHNIQUE FOR MEASUREMENT OF REFRACTIVE-INDEX AND ABSORPTION-COEFFICIENT SIMULTANEOUSLY WITH SIZE AND VELOCITY

The principle of the dual burst technique (DBT) based on phase-Doppler anemometry (PDA) is proposed for simultaneous particle refractive ind ex, size and velocity measurements. This technique uses the trajectory effects in PDA systems to separate the two contributions of the diffe rent scattering processes. In the case of forward scattering and refra cting particles, it is shown that from the phase of the reflected cont ribution, the particle diameter can be deduced, whereas from the refra cted contribution the particle refractive index and velocity can be ob tained. Furthermore, the intensity ratio of these two scattering proce sses can be used for absorption measurements. Simulations based on gen eralized Lorenz-Mie theory and experimental tests using monodispersed droplets of different refractive indices and absorption coefficients h ave validated this technique.