A combined laser Doppler anemometry and electrical probe diagnostic for bubbly two-phase flow

A review of the literature on laser Doppler anemometry (LDA) techniques to discriminate liquid from bubble velocities reveals that the techniques are unsuitable for large bubbles at moderate void fractions. A statistical technique, based on the separation of the combined gas and liquid velocity distribution function, was investigated. It was found to be appropriate for uniformly sized bubbles, a condition which is most easily achieved with small bubbles (<4 mm dia). A combined LDA and electrical probe (EP) technique was also developed to simultaneously measure the velocities from both the liquid and gaseous phase in unconfined two-phase bubbly plumes. The simultaneous time series of LDA velocities and EP signals from a chain of bubbles permitted separation of gas and liquid velocities at high volume fractions and for large, irregular bubbles.