A dynamic model for the Lagrangian stochastic dispersion coefficient

Abstract

A stochastic sub-grid model is often used to accurately represent particle dispersion in turbulent flows using Large Eddy Simulations. This type of models have a free parameter, the dispersion coefficient, which is not universal and is strongly grid-dependent. In the present paper, a dynamic model for the evaluation of the coefficient is proposed and validated in decaying homogeneous isotropic turbulence. The grid dependence of the static coefficient is investigated in a turbulent mixing layer and compared to the dynamic model. The dynamic model accurately predicts dispersion statistics and resolves the grid-dependence. Dispersion statistics of the dynamically calculated constant are more accurate than any static coefficient choice for a number of grid spacings. Furthermore, the dynamic model produces less numerical artefacts than a static model and exhibits smaller sensitivity in the results predicted for different particle relaxation times.

Numerical and experimental investigation on droplet dynamics and dispersion of a jet engine injector

“…3 (c) with a cell size of 400 µm was used to guarantee an adequate resolution of eddy length. However, the effects of small turbulent structures within the unresolved subgrid-scale, as studied in (Jones et al, 2012(Jones et al, , 2014Pesmazoglou et al, 2013), were not considered in this work. The influence of the subgrid-velocity on droplet dispersion is typically negligible in jet engine injectors (Apte et al, 2003).…”

Large eddy simulation of particle aggregation in turbulent jets

“…In the present work, the aggregation model presented by Pesmazoglou et al (2016) is coupled to Large Eddy Simulations (LES), using the spray-pdf approach by Williams (1958). The aggregation model was validated against analytic solutions Pesmazoglou et al (2016), the spray-pdf approach was validated by Pesmazoglou et al Pesmazoglou et al (2013) Pesmazoglou et al (2014). The model focuses on applications with large numbers of particles in the domain, > O(10 8 ), mostly on the nano-scale, where one-to-one collision approaches are intractable.…”

Large-eddy simulation of turbulent dispersed flows: a review of modelling approaches

“…There are several other formulations available in the open literature (see e.g. [3,12,92,126,127]), which are also based on Eq. (20) but adopt different correlations for the timescale τ SG S and for the diffusion term constant C 0 .…”