Method of phase-Doppler anemometry free from the measurement-volume effect

A novel method is developed to improve the accuracy of particle sizing in l aser phase-Doppler anemometry (PDA). In this method the vector sum of refra ctive and reflective rays is taken into consideration in describing a dual- mechanism-scattering model caused by a nonuniformly illuminated PDA measure ment volume. The constraint of the single-mechanism-scattering model in the conventional PDA is removed. As a result the error caused by the measureme nt-volume effect, which consists of a Gaussian-beam defect and a slit effec t, can be eliminated. This new method can be easily implemented with minima l modification of the conventional PDA system. The results of simulation ba sed on the generalized Lorenz-Mie theory show that the new method can provi de a PDA system free from the measurement-volume effect. (C) 1999 Optical S ociety of America.