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A numerical methodology to simulate the high pressure spray evolution and the fuel-air mixing in Diesel engines is presented. Attention is focused on the employed atomization model, a modified version of the Huh and Gosman, on the definition of a turbulence length scale limiter and of an adaptive local mesh refinement technique to minimize the result grid dependency. All the discussed models were implemented into Lib-ICE, which is a set of libraries and solvers, specifically tailored for engine simulations, which runs under the open-source CFD technology OpenFOAM

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and available online here Cet article fait partie du dossier thématique ci-dessous publié dans la revue OGST, Vol. 69, n°1, et téléchargeable ici D o s s i e rDOSSIER Edited by/Sous la direction de : C. Angelberger IFP Energies nouvelles International Conference / Les Rencontres Scientifiques d'IFP Energies nouvelles LES4ICE 2012 -Large Eddy Simulation for Internal Combustion Engine FlowsLES4ICE 2012 -La simulation aux grandes échelles pour les écoulements dans les moteurs à combustion interne Oil & Gas Science and Technology -Rev. IFP Energies nouvelles, Vol. 69 (2014) des e´coulements froids dans des ge´ome´tries complexes, comme dans les cylindres des moteurs a`combustion interne. L'imple´mentation de conditions aux limites a`l'entre´e pour la ge´ne´ration de turbulence synthe´tique et de deux mode`les des e´chelles infe´rieures a`la maille, le mode`le local dynamique de Smagorinsky et le mode`le SGS (Sub-Grid Scales) de viscosite´WALE (Wall-Adapting Local Eddy), est de´crite. Le mode`le WALE est baseś ur le carre´du tenseur du gradient de vitesse. Il prend en compte a`la fois les effets de la pression et du taux de rotation des plus petites fluctuations turbulentes de´tectables et il de´crit de manie`re ade´quate l'e´chelle y 3 a`proximite´des parois de la viscosite´turbulente sans ne´cessiter de pression dynamique. Il est ainsi cense´repre´senter un mode`le tre`s fiable pour les simulations ICE. La validation du mode`le a e´te´effectue´e sur deux bancs laminaires stationnaires : une ge´ome´trie a`gradin inverse´(backward-facing) et une ge´ome´trie simple de moteur a`combustion interne avec une unique vanne centrale. L'exhaustivite´de la simulation LES (i.e. la qualite´de la simulation LES) est aussi discute´e.Abstract -Boundary Conditions and SGS Models for LES of Wall-Bounded Separated Flows: An Application to Engine-Like Geometries -The implementation and the combination of advanced boundary conditions and subgrid scale models for Large Eddy Simulations are presented. The goal is to perform reliable cold flow LES simulations in complex geometries, such as in the cylinders of internal combustion engines. The implementation of an inlet boundary condition for synthetic turbulence generation and of two subgrid scale models, the local Dynamic Smagorinsky and the Wall-Adapting Local Eddy-viscosity SGS model (WALE) is described. The WALE model is based on the square of the velocity gradient tensor and it accounts for the effects of both the strain and the rotation rate of the smallest resolved turbulent fluctuations and it recovers the proper y 3 near-wall scaling for the eddy viscosity without requiring dynamic pressure; hence, it is supposed to be a very reliable model for ICE simulation. Model validation has been performed separately on two steady state flow benches: a backward facing step geometry and a simple IC engine geometry with one axed central valve. A discussion on the completeness of the LES simulation (i.e. LES simulation quality) is given.

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