Multiscale Simulation of Bubbly Flows

Large eddy simulation coupled with a Lagrangian bubble tracker is used to investigate the dynamics of a liquid containing microbubbles in a turbulent, horizontal channel flow. Such flows are relevant in a number of engineering and environmental applications, including bubble columns, gas-liquid reactors, fluidised beds and fluid transfer in pipelines. Sub-grid scale stresses are parameterised using a dynamic model, with the microbubbles assumed to be spherical and non-deformable, and subject to drag, lift, gravity, buoyancy, added mass and pressure gradient forces. The bubbles are also momentum-coupled with the carrier fluid. A channel flow of water at a shear Reynolds number, Reτ = 150, and bubble diameter, d = 80 μm, is considered. Results are consistent with those from previous direct numerical simulations, and demonstrate bubble migration towards the upper channel wall with time due to buoyancy effects, and the associated impact on the flow velocity and bubble concentration distribution.