Drag and lift forces acting on a spherical gas bubble in a homogeneous linear shear flow were numerically investigated by means of a three-dimensional direct numerical simulation (DNS) based on a marker and cell (MAC) method. The effects of fluid shear rate and particle Reynolds number on drag and lift forces acting on a spherical gas bubble were compared with those on a spherical inviscid bubble. The results show that the drag force acting on a spherical air bubble in a linear shear flow increases with fluid shear rate of ambient flow. The behaviour of the lift force on a spherical air bubble is quite similar to that on a spherical inviscid bubble, but the effects of fluid shear rate on the lift force acting on an air bubble in the linear shear flow become bigger than that acting on an inviscid bubble in the particle Reynolds number region of 1≤Rep≤300. The lift coefficient on a spherical gas bubble approaches the lift coefficient on a spherical water droplet in the linear shear air-flow with increase in the internal gas viscosity.
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