Turbulence Measurements in Two-Phase Bubbly Flows Using Laser Doppler Anemometry

An accurate and reliable laser Doppler anemometer technique (L.D.A.) was developed to measure the characteristics of two-phase bubbly flows. Most of these characteristics are the various statistical moments of the velocity fluctuations and the Reynolds stress tensor components within the continuous phase but also, under well defined conditions, the mean relative velocity of the dispersed phase. Although this technique was applied to a turbulent cocurrent vertical air-water bubbly flow, it is believed that it can be extended to many other two-phase dispersed flow patterns, since a wide variety of experimental conditions was successfully explored: the mean liquid velocity and the local void fraction ranged respectively from 0 to 1.2 m/s and from 0 to 7%, while the mean bubble diameter was of the order of 5 mm. Moreover, experiments were carried out in a large test section (450 × 450 mm2), i.e. in the least favourable situation for such measurements. The technique employed is derived from the classical differential Doppler detection and forward diffusion method, which is adapted to the case of a bubbly flow by choosing the appropriate signal processing method. Comparison with results previously obtained in the same facility with a conical hot film anemometer clearly demonstrates the accuracy of the method. All the details concerning this work can be found in the article by Marie (1983).