LDA experiments on a mixing layer

Abstract

Investigation on plane turbulent two phase mixing layers serves to get insight in the mutual interaction between the behaviour of the injected gas bubbles and the turbulence of the liquid phase. An experimental setup for investigations on such a mixing layer has been built. The measuring section is 20 cm in depth, 40 cm in width, and 150 cm in height. Measurements have been done on the liquid phase (water) with use of Laser Doppler Anemometry. These measurements mainly serve to determine the quality of the setup. The LDA measurements relate, first, to averaged velocities and their profiles, and second, to turbulent quantities, viz. rms values and ttu-stresses. From the turbulent quantities, ID-spectra and autocorrelation functions have been determined. As a direct result of the measurements, the air distribution was improved. The experimental results indicate that a leakage between the two sections exists. This should be repaired, along with the obliquity of the splitter plate. To get more reliable spectra, the data rate of the LDA measurements has to be increased. Another requirement for future measurements is the use of an accurate and more stable traverse system for the LDA probe.