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Abstract: A 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. The model consisted of Reynolds-averaged Navier–Stokes (RANS) transport equations, a standard k–ω 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 the density ratio effect on the drag reduction was carried out. The study indicated that simple mixture density variation effect plays one of the major roles in the microbubble drag reduction phenomenon. Also, the influence of the density ratio (the ratio of density of injected gas to that of water) on gas volume fraction profiles was found to be minimal within studied parameter range. [Copyright &y& Elsevier]

In this paper, a simplified 3D algebraic slip mixture (ASM) model is introduced to obtain the numerical solution in sand–water slurry flow. In order for the study to obtain the precise numerical solution in fully developed turbulent flow, the RNG K–ϵ turbulent model was used with the ASM model. An unstructured (block-structured) non-uniform grid was chosen to discretize the entire computational domain, and a control volume finite difference method was used to solve the governing equations. The mean pressure gradients from the numerical solutions were compared with the authors’ experimental data and that in the open literature. The solutions were found to be in good agreement when the slurry mean velocity is higher than the corresponding critical deposition velocity. Moreover, the numerical investigations have displayed some important slurry flow characteristics, such as volume fraction distributions, slurry density, slip velocity magnitude, slurry mean velocity distributions, and slurry mean skin friction coefficient distributions in a fully developed section, that have never been displayed in the experiments. [Copyright &y& Elsevier]