The impact of high order refraction on optical microbubble sizing in multiphase flows

High order refractions have been found to have a great impact on optical particle sizing using phase-Doppler anemometry (PDA) especially when the relative refractive index of the media is less than one. The high order refractions cannot be neglected because of the differences in spatial frequencies and motion directions of each order. A model of phase-size correlation is proposed that considers these high order refractions. By using the conversion factors of the high order refractions, the particle diameter can be determined. The capability of the newly developed method was evaluated by using generalized Lorenz Mie theory (GLMT), which was validated by experiments. The results of the simulation and experiments are compared with those based on the conventional method. An optimization method for accurately sizing air bubbles in water has been suggested.