Principles of LDA for Two-Phase Flows

The angle P is a function of L/R and 0. Since L/R is usually large and 0 is small it follows that also that P is small and Equation 7.1 yields the universal equation of laser Doppler anemometry  

for large values of L/R one obtains the classical equation of LDA. 

The findings described above are the basis for the application of LDA for particle velocity measurements in two-phase flows. A pre-requisite for successful applications of LDA for velocity measurements in two-phase flows is an unhindered optical access, putting a constraint on the permissible volume concentration and/or penetration depth. Nevertheless, numerous studies have 

Since the scattering intensity depends additionally on refractive index and particle shape, particle sizing based on intensity measurements generally requires calibration. 

Moreover, it is important to note that the intensity of the diffracted light is independent of the optical constants of the particle material, which is an advantage in sizing particles of different or unknown refractive index. 

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