Turbulence structure under a typical shear induced wave at a liquid/gas interface

Abstract

The turbulence structure of the liquid phase in a stratified two phase flow with a wavy interface was experimentally investigated in a 50 mm (H) {times} 100 mm (W) rectangular duct. Variable Interval Time Averaging with a positive slope was used to calculate the frequency of occurrence of organized motions from the velocity signals obtained with a two channel hot film anemometer. Experimental results showed that turbulence generation at the interface is dominated by the shear imposed at the free surface and the waves produced at the interface. Also, large scale cellular motions extending deep into the bulk of the liquid flow, which roll in the flow direction and sweep the entire liquid depth were detected. These cellular motions are stronger under the waves with greater amplitude. Detected large scale cellular motions are responsible for increased scalar transfer coefficients across a wavy sheared interface. It was shown that the frequency of occurrence of organized motions in both wall and free surface regions would increase with the increasing shear at the interface.