ID 74

A new LES subgrid-scale approach for turbulence modulation by droplets

 

Abstract:

We present a new modelling approach for turbulence modulation by droplets on the subgrid-scale (SGS) level of Large-Eddy-Simulations (LES). Many SGS models exist for the effect of gas phase SGS on the droplet phase, but very few for the mechanisms vice versa on the turbulent intensity of the gas phase. The reasons are a lack of physical understanding and limited computational resources for extensive DNS studies. To address both problems a dimension-reduced and consequently less costly model, namely One-Dimensional- Turbulence (ODT), is used to gather information about this specific flow phenomena. ODT is a stochastic tool simulating turbulent flows along a notional 1D line of sights. For modeling the turbulent advection instantaneous maps are applied to the line which represent the effect of individual eddies on property fields and the dispersed phase. After validating the general test case of a droplet-laden shear flow against DNS data, a concept is presented on how to gather turbulence modulation for several parameter ranges in a data base and how to make them accessible on the flight for LES. The three most significant parameters, the unladen flow Reynolds number, the droplet loading and the particle momentum number, are chosen to construct an efficient data base.