Abstract
A variety of gas-liquid two-phase flow patterns observed in a horizontal channel is introduced in the paper. The motivation of the experiment originates from drag reduction technique development for marine vessels in sea water, which requires physical mechanism toward practical utilization. The authors' group carried out high-speed air-water mixture visualization as well as low-speed silicone oil loop experiment so that what the figure of the gas-liquid interfaces imply when we discuss about the mechanism. The series of visualization showed multiple novel interpretation of the mechanism; spanwise clustering of bubbles takes place in laminar bubbly two-phase flow, streamwise striping of bubble distribution is formed in turbulent condition, and chained bubbles with large deformation appear at the intermediate conditions. The difference of the bubble clustering is understood to have a correlation to wall shear stress that has been reduced when clustering becomes strong.
