単一中間サイズ気泡の抵抗低減効果に対する直接数値シミュレーション

抄録

Air lubrication systems have gained considerable popularity as a promising drag reduction technology in recent years. However, the numerical simulations of intermediate-sized bubbles is quite challenging because of the numerical diffusion of the conventional method and the high deformability of the bubbles. This hinders the study of the physical mechanisms involved in a variety of phenomena in such types of bubbles, such as the bubble–liquid interaction effect, high bubble deformation, and flow in the liquid film generated above the bubble. In this study, direct numerical simulation is conducted for intermediate-sized bubble in turbulent channel to investigate the drag reduction around the bubble. To capture sharp-interface between gas and liquid, a solver viz. interIsoFoam of OpenFOAM, which is directly captured by the improved Volume of Fluid method, was applied. The numerical results for skin friction trends around the bubble are shown as the Weber number. The drag reduction is achieved from rear part of liquid film and frontside of secondary flow.