ID 296

Assessment of the grid requirements for the modelling of the dynamics of high speed evaporating sprays using LES / Eulerian-Lagrangian frameworks

 

Abstract:

The physics of high speed liquid jets injected in elevated temperature and pressure conditions are extremely complex due to the multi-scale and multi-phase flow characteristics. Large eddy simulations (LES) are widely applied for simulations of multi-phase flows because large scale mixing of ambient air with the liquid vapour (when evaporation is occurring) is better captured than other traditional CFD techniques, such as Reynolds Averaged Navier-Stokes. However, in order the LES predictions to be accurate, in addition to the required numerical accuracy of the solvers and the effect of sub-grid scale (SGS) models, the mesh dependence needs to be addressed when the mesh refinement is not enough due to limited computing resources. This work uses as the basis for our analysis fuel spray simulations of n-dodecane under non-reacting conditions injected in a high pressure, high temperature constant chamber known as "Spray A". Although previous works have presented the effect the grid has on the accuracy of the results based on "trial and error" basis, no insight of the dynamics of each phase was provided in the same conditions under different grids. In our work the novelty lies in the fact that the observed trends of each phase regarding to the mesh size are explained based on the code numerics and linked to the physics of the flow. It aims to improve the understanding of the role of mesh refinement in multi-phase coupling characteristics and to provide a guideline for mesh resolution requirements of high speed evaporating sprays within LES/Eulerian Lagrangian approaches.