Abstract Owing to different flow conditions—for example, Poiseuille and Couette flow—one could expect different deformations of large-sized bubbles; however, bubble dynamics has been mostly investigated in channel flow. Consequently, an intermediate flow condition shared by both the channel and ship surface is needed for large-sized bubbles, although it can be difficult to simultaneously generate turbulent Couette flow in the channel and measure the shear stress on the ship’s surface experimentally. In this study, large-sized bubbles in turbulent Couette flow were investigated numerically to determine their common characteristics under such flow conditions. The interIsoFoam solver from OpenFOAM—which can directly capture the interface via the geometric volume of fluid method—was used to conduct the simulations of the gas–liquid interface problem. The turbulent Couette flow was driven by top wall velocity condition with an initial perturbation, and three different bubble sizes with Weber numbers in the range of 200–300 were chosen to determine the characteristics of large-sized bubbles. By monitoring the results according to bubble size, we could determine bubble characteristics that were distinguishable from those in turbulent Poiseuille flow. Consequently, bubble deformation was dominated by the velocity gradient and shear rate, which was greater than that during single-phase flow from the liquid-film region. These results allowed us to generalize the deformation mechanism of large-sized bubbles in turbulent Couette flow into five categories—namely, the initial shape, deformation on the front side, change of the center of gravity, pinch-off/breaking of the ligament, and deformation to a stable shape.Graphical abstract
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