Validation of a zonal hybrid URANS/LES turbulence modeling method for multi-cycle engine flow simulation

Abstract

A zonal hybridization of the RNG [Formula: see text]-[Formula: see text] URANS model is proposed for the simulation of turbulent flows in internal combustion engines. The hybrid formulation is able to act as URANS, DES or LES in different zones of the computational domain, which are explicitly set by the user. The resulting model has been implemented in a commercial computational fluid dynamics code and the LES branch of the modified RNG [Formula: see text]-[Formula: see text] closure has been initially calibrated on a standard homogeneous turbulence box case. Subsequently, the full zonal formulation has been tested on a fixed intake valve geometry, including comparisons with third-party experimental data. The core of the work is represented by a multi-cycle analysis of the TCC-III experimental engine configuration, which has been compared with the experiments and with prior full-LES computational studies. The applicability of the hybrid turbulence model to internal combustion engine flows is demonstrated, and PIV-like flow statistics quantitatively validate the model performance. This study shows a pioneering application of zonal hybrid models in engine-relevant simulation campaigns, emphasizing the relevance of hybrid models for turbulent engine flows.

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

“…where ∆ is a grid-related filter length scale and C DES ≈ O(1). The ∆ parameter is calculated as the cubic root of the computational cell volume, while C DES is set to 0.61 [27]. As stated above, the expressions (5) and 6are general and can be applied to any URANS form, by just adapting l RANS accordingly.…”

“…The bore × stroke values are equal to 92 × 86mm, with a (nominal) compression ratio of 10:1. This engine has already been the object of extensive numerical studies by the authors [26,27,35,36], in which the zonal hybrid methodology shown above has been implemented into the STAR-CD software [37] and then assessed and validated on a relatively fine computational grid (2×10 6 elements at the BDC). Nonetheless, a head-to-head comparison between the DES and DESx modes of operation was still missing and is, therefore, proposed here.…”

“…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]. Most of the studies currently reported in the scientific literature are based on the Detached-Eddy Simulation (DES) concept and its derivatives [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27], while a few of them relies on the Scale-Adaptive Simulation (SAS) approach [15,16,28,29].…”

3D-CFD Simulation of a GDI Injector Under Standard and Flashing Conditions

“…In this panorama, a crucial role is played by CFD analyses which allow to reduce time-and cost-to-market thanks to a proper prediction of the knock onset. Simulations are based, on the one hand, on reliable knock models [12][13][14][15][16] and, on the other hand, on a robust numerical framework able to fairly reproduce flow field, cycle-to-cycle variability, heat transfer, spray, film formation, fuel chemistry and combustion [17][18][19][20][21][22][23][24][25][26][27][28].…”

Evaluation of a Scale-Resolving Methodology for the Multidimensional Simulation of GDI Sprays

“…Broadly speaking, a hybrid URANS/LES method should be based on the ability to adapt its behavior by applying the best-fitting modeling option with respect to the available numerical resolution. In the past 10 years, the number of engine-related hybrid modeling applications has been constantly increasing [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26], but hybrid/LP investigations are almost absent [27,28]. In our study, we evaluated two previously developed hybrid scale-resolving approaches [21,24,28,29] for a computational analysis of the "Spray G" reference GDI injector [30].…”