SIMULATION OF COALESCENCE, BREAK UP AND MASS TRANSFER IN GASLIQUID SYSTEMS BY USING MONTE CARLO AND QUADRATURE-BASED MOMENT METHODS

The description of the fluid-dynamics and of mass transfer in gas-liquid systems requires the evaluation of bubble size and composition distributions, dictated by bubble breakage, coalescence and mass exchange with the liquid phase. In our previous work, gas-liquid systems were investigated by coupling CFD with mono-variate population balance equation (PBE) solved with the quadrature method of moments (QMOM). The problem is here extended to the solution of multi-variate PBE. In this work the Conditional Quadrature Method of Moments (CQMOM) is for the first time validated by comparison with Direct Simulation Monte Carlo (DSMC). Results, obtained from the comparison of the two methods, show that the quadrature approximation implicitly used in CQMOM for overcoming the closure problem is very accurate. CQMOM is then implemented in ANSYS/Fluent and OpenFoam and predictions are compared with experiments, resulting in very good agreement.