Lagrangian statistics of bubbles in a turbulent boundary layer

We are developing the capability to simulate bubbly flows in complex geometries using unstructured grids and an Euler--Lagrangian methodology. In the Lagrangian bubble model, the bubbles are treated as a dispersed phase in the carrier fluid, and individual bubbles are point--particles governed by an equation for bubble motion. The behavior of the bubble radius is determined by integrating the Rayleigh--Plesset equation. For this talk, direct numerical simulation is used to solve the Navier--Stokes equations for a spatially--evolving turbulent boundary layer ($Re_{\theta}\!=\!600\!-\!1800$) and bubbles are injected into the near-wall region. Except for the Reynolds number, the simulation matches all parameters of an experiment by Sanders, {\it et al.}\ (J. Fluid Mech., 2006). The bubbly suspension is dilute and one--way coupled equations are used. The temporal evolution of the bubble dispersion, probability density functions of the forces on a bubble and void--fraction profiles will be presented, and the impact of bubble behavior on drag reduction and the effect of cavitation number will be discussed.