Multiscale computations of mass transfer from buoyant bubbles

Mass transfer in the liquid phase of gas–liquid multiphase flows usually takes place at a considerably slower rate than the transfer of momentum, so mass flux boundary layers are much thinner than momentum boundary layers. In Direct Numerical Simulations (DNS) the resolution requirement for flows with mass transfer are therefore significantly higher than for flow without mass transfer. Here we develop a multiscale approach to compute the mass transfer from buoyant bubbles, using a boundary-layer approximation next to the bubble and a relatively coarse grid for the rest of the flow. This approach greatly reduces the overall grid resolution required.

► Direct numerical simulation of high Schmidt number two phase flows.
► Boundary layer description of mass transfer at the phase boundary.
► The necessary grid resolution is reduced significantly, especially for high Schmidt numbers.
► The accuracy of this approach is demonstrated by comparison with fully resolved results.