前後非対称な楕円形状を有する気泡に働く抗力

抄録

Direct simulations are performed for a deformable bubble rising steady through a quiescent viscous fluid for different Reynolds and Weber numbers. The axi-symmetric Navier-Stokes equations for the liquid phase are solved on a boundary-fitted mesh, which allows an accurate prediction of the bubble shape and the drag force acting on the bubble. The drag coefficients are in excellent agreement with previous experimental data, while the deviation of the Moore's theory from these numerical and experimental results is found to increase with decrease of the Reynolds number and with increase of the bubble aspect ratio. It is revealed that neither the fore-aft asymmetry nor the presence of a standing eddy at the rear of the bubble is of primal importance to the drag force.