Turbulence in two-phase bubbly flow

Two-dimensional turbulence measurements in air-water two-phase bubbly flow in a pipe using a dual-sensor hot-film anemometry are presented. In contrast to the authors' previous work, the turbulence is highly promoted by the existense of bubbles. And the data confirm the roughly isotropic behaviour for highly turbulent bubbly flow conditions. The effect of bubble-induced velocity fluctuations is discussed based on the turbulence intensity measurements and was found to increase as a 0.8 power of the void fraction. The measured turbulent shear stress shows the highest values in the wall proximity, corresponding to the maxima in the phase distribution. This reflects the enhanced turbulence energy producing there. Eddy diffusivity correlations are proposed to predict profiles of liquid velocity and turbulent shear stress. Finally, the turbulence energy spectra for axial and lateral velocity components u and v, and that for shear stress term uv are calculated, using Fast Fourier Transform techniques. Results show an augmentation of high frequency component for bubbly two-phase flow conditions. Macro and micro scales are also measured and discussed. (orig.)