SIMULTANEOUS MEASUREMENT OF LIQUID-FILM THICKNESS, WALL SHEAR-STRESS AND GAS-FLOW TURBULENCE OF HORIZONTAL WAVY 2-PHASE FLOW

Wall shear stress, liquid film thickness and streamwise gas velocity are measured simultaneously, respectively, with a hot-film, conductance probe and hot-wire at a fully developed location of air-water wavy two-phase flow in a horizontal tube. A conditional sampling technique is applied to eliminate the effect of wire-wetting on the output signal of the hot-wire anemometer. A gradual decrease and successive rapid increase in the gas velocity are clearly observed just before large wave peaks are detected. Minimum gas velocities caused by several waves are lower than the propagation velocity of each wave. This may suggest the existence of a separation bubble attached to the front of large waves. An increase in the wall shear stress caused by the passing of large waves is also observed.