Direct numerical simulations of drag and lift forces acting on a spherical bubble near a plane wall

The drag and lift forces acting on an inviscid bubble moving near a plane wall in a quiescent liquid were numerically investigated using a three-dimensional direct numerical simulation (DNS) based on the marker and cell (MAC) method. The numerical results showed that the presence of the wall causes an increase in the drag force. The direction of the lift force acting on a bubble near the wall changed depending on the Reynolds number and the distance between the bubble and the wall. At low Reynolds numbers, the wall-induced lift coefficient of a bubble was positive, causing the bubble to move away from the wall. In contrast, at high Reynolds numbers, the negative wall-induced lift force appeared at a position away from the wall, although the wall-induced lift force became positive in the immediate vicinity of the wall. It seems that this direction change in the lift force causes the bouncing motion of the bubble, as reported by Takemura and Magnaudet (2003).