Density Ratio and Turbulence Intensity Effects in Microbubble Drag Reduction Phenomenon

Two-dimensional single phase computational fluid dynamics (CFD) model of microbubble-laden flow over a flat plate was used to assess the role of mixture density variation in microbubble drag reduction for high Reynolds number flows. The model consisted of Reynolds-averaged Navier-Stokes (RANS) transport equations, a standard k-ε turbulence model, and a convection-diffusion species transport model. Performance of the model was validated with available experimental data and numerical simulations of more advanced multiphase two-fluid model. A parametric study of density ratio and free stream turbulence intensity effects on drag reduction was carried out. The study indicated that the model taking into account only mixture density effect could still predict drag reduction reasonably well. In addition to this, higher values of free stream turbulence intensity are predicted to result in lower drag reduction.