Standard and consistent Detached-Eddy Simulation for turbulent engine flow modeling: an application to the TCC-III engine

Vesselin Krassimirov Krastev,Clara Iacovano,Alessandro D’Adamo,Stefano Fontanesi,Giovanni Di Ilio

doi:10.1051/e3sconf/202019706021

Abstract

Multidimensional modeling of Cycle-to-Cycle Variability (CCV) has become a crucial support for the development and optimization of modern direct-injection turbocharged engines. In that sense, the only viable modeling options is represented by scale-resolving approaches such as Large Eddy Simulation (LES) or hybrid URANS/LES methods.Among other hybrid approaches, Detached-Eddy Simulation (DES) has the longest development story and is therefore commonly regarded as the most reliable choice for engineering-grade simulation. As such, in the last decade DESbased methods have found their way through the engine modeling community, showing a good potential in describing turbulence-related CCV in realistic engine configurations and at reasonable computational costs.In the present work we investigate the in-cylinder modeling capabilites of a standard two-equation DES formulation, compared to a more recent one which we call DESx. The DESx form differs from standard DES in the turbulent viscosity switch from URANS to LES-like behavior, which for DESx is fully consistent with Yoshizawa’s one-equation sub-grid scale model. The two formulations are part of a more general Zonal-DES (ZDES) methodology, developed and validated by the authors in a series of previous publications. Both variants are applied to the multi-cycle simulation of the TCC-III experimental engine setup, using sub-optimal grid refinement levels in order to stress the model limitations in URANS-like numerical resolution scenarios. Outcomes from this study show that, although both alternatives are able to ouperform URANS even in coarse grid arrangements, DESx emerges as sligthly superior and thus it can be recommended as the default option for in-cylinder flow simulation.

Highlights

IntroductionAfter thirty years of development, hybrid URANS/Large Eddy Simulation (LES) turbulence models are considered a powerful and reliable tool for the numerical description of a large variety of turbulent flows
We focus the attention on the x = 0 plane, which represents a cross-cut of the large intake vortex structures and is, the most suitable for a careful analysis of the three-dimensional flow evolution
The computed numerical data sets include 50 consecutive engine cycles, with the flow field evaluated at three selected crank angle values, that is: 475 degrees, equivalent to the intake valve maximum lift; 540 and 630 degrees, equivalent to BDC and mid-compression stroke, respectively

Summary

Introduction

After thirty years of development, hybrid URANS/LES turbulence models are considered a powerful and reliable tool for the numerical description of a large variety of turbulent flows. Aside from wing aerodynamics, current typical examples of engineering-grade hybrid URANS/LES applications include full-scale turbomachinery, ship hydrodynamics, aeroacoustics, large-scale urban flows and jet propulsion [2,3,4,5,6]. But with a rapidly evolving track record in the past ten years, is the implementation of hybrid URANS/LES models for the scale-resolving simulation of flow through internal combustion engines [7]. The main reason for considering hybrid approaches for engine modeling is the increasingly compelling need for high-quality time and space resolved numerical data sets, but at a reduced computational cost compared to standard LES, as outlined in [8,9,10,11]. The remainder of the paper includes two more sections, one devoted to a brief description of the method and equations involved and the last one showing the simulation setup and results

Standard and consistent RNG k-ε DES formulations

Zonal-DES implementation

Conclusions