Canadian Journal of Chemical Engineering, Vol.85, No.2, 137-150, 2007
An improved les on dense particle-liquid turbulent flows using integrated Boltzmann equations
An improved large eddy simulation (LES) using a dynamic second-order subgrid stress (SGS) model has been developed for simulating dense particle-liquid two-phase turbulent flows. The governing equations of each phase are obtained from a microscopic point of view, using the kinetic theory of molecular gas. They are derived by multiplying the Boltzmann equation of each phase by property parameters and integrating over the velocity space. An inter-particle collision term is included in the governing equation of the particle phase. Assuming a Maxwellian distribution of the velocity for particle-phase, an inter-particle collision term is derived. A dynamic second-order SGS model is used in the LES to solve the governing equations. The coefficients of the second-order SGS model are obtained from the criteria of dimensional consistency and the invariants of strain-rate and rotation-rate tensors. During the simulation, the finite volume method (FVM) is used to discritize the governing equations with a staggered grid system. Continuity is conserved by the application of a mass-weighted method to the filtered governing equation. The SIMPLEC algorithm is used to solve the discretized governing equations. Body-fitted coordinates are used to simulate two-phase flows in complex geometries. This dynamic second-order SGS model has been successfully applied to simulate the dense particle-liquid two-phase turbulent flows in a centrifugal impeller and a duct. The simulated pressure and velocity distributions are in good agreement with experimental results.
Keywords:large eddy simulation;dense particle-liquid turbulent two-phase flows;integrated Boltzmann equation;second-order subgrid stress model;pump impeller and duct