LES and URANS modelling of turbulent liquid—liquid flowin a static mixer:Turbulent kinetic energy and turbulence dissipation rate

摘要

The present study deals with numerical simulations of turbulent flow of a liquid-liquid system ina Kenics static mixer with ten inserts. CFD approach was used in two modes: large eddy simulation(LES) and unsteady Reynolds averaged Navier—Stokes (URANS). Large eddy simulation in thestatic mixer was carried out using the dynamic kinetic energy subgrid-scale model with standardwall functions whereas in URANS approach the standard k-s turbulent model and standard wallfunctions were applied. Two-phase flow was modelled employing the "mixture model" of the Euleriantype. The simulations were performed mainly for the Reynolds number of 10000 with the volumetricratio of 99 % of water to 1 % of oil. The investigations revealed that due to distinct distributionsof the turbulence measures, the drop breakup process occurs with varying intensity in differentlocations within the mixer inserts. Significantly higher local values of the dissipation rate, E, werepredicted in URANS than in LES. However, both modelling methods indicated high values of v atthe beginning and the end of the mixer inserts, which implies the maximum shearing action exertedon the drops. Consequently, the inflow and outflow zone of each insert are the regions of the highestbreakup intensity.