Lagrangian-Eulerian correlation functions

Turbulent flows the particle phase is usually modelled by using diffusion theory. This means that the particle phase is described by a convention-diffusion equation for the particle concentration where the eddy-diffusivity concept is invoked in order to model the interaction between the turbulent fluid velocity and the particle concentration. It is well-known that this concept is only a crude approximation, in which the eddy diffusivity has to be fitted for each new application. In this project we intend to describe the particles by a stochastic Langevin equation. The coefficients in this equation can be found form langrangian velocity correlation functions calculated by means of DNS. Further, ways to model the particle-turbulence interactions in large-eddy simulation are studied.