Boundary Conditions and SGS Models for LES of Wall-Bounded Separated Flows: An Application to Engine-Like Geometries

Piscaglia, F.; Montorfano, A.; Onorati, Angelo; Brusiani, Federico

doi:10.2516/ogst/2013143

Cited by 17 publications

(14 citation statements)

References 31 publications

(51 reference statements)

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“…It was found that LSR provides a more precise estimation of the local grid resolution and may provide hints about the overall simulation quality [22,23]. Experience showed that LSR ≤ 5 can be used as a quality threshold to assess local mesh resolution.…”

Section: Averaged Fieldsmentioning

confidence: 95%

“…LES was performed using the finite volume CFD code OpenFOAM [31], which was extended for this work by the WALE subgrid scale (SGS) model in its compressible formu- [23] and by an improved mesh motion strategy, which is particularly suitable for IC engines [14,21].…”

Section: Large Eddy Simulationmentioning

confidence: 99%

“…In particular, the DNS code was was extended with an arbitrary Lagrangian/Eulerian approach (ALE) to account for moving grids, while specific sub-models for LES were implemented by the authors in the OpenFOAM technology [18][19][20]23] and were used in the present work; modifications included the implementation of a compressible WALE subgrid-scale model [17], improvements to the mesh motion strategy [14,21,22] and appropriate boundary and initial conditions for LES which includes turbulent structures (generated artificially at the boundary), with physically sound spatial and temporal correlations [13]. Algorithms for data post-processing methods like the Proper Orthogonal Decomposition (POD) have also been implemented [15].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Comparison of Direct and Large Eddy Simulations of the Turbulent Flow in a Valve/Piston Assembly

Montorfano

Piscaglia

Schmitt

et al. 2015

Flow Turbulence Combust

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Section: Averaged Fieldsmentioning

confidence: 95%

Section: Large Eddy Simulationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Comparison of Direct and Large Eddy Simulations of the Turbulent Flow in a Valve/Piston Assembly

Montorfano

Piscaglia

Schmitt

et al. 2015

Flow Turbulence Combust

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“…Several efforts have been devoted to implement solution-adaptive gridding methodology (Pope, 2004;Celik et al, 2005;Brusiani and Bianchi, 2008;Davidson, 2009;Piscaglia et al, 2014;Xiao et al, 2014), however, here we only undertook an assessment of the results quality after the grid was prescribed.…”

Section: Assessment Of Les Results Qualitymentioning

confidence: 99%

Large-Eddy Simulation (LES) of Spray Transients: Start and End of Injection Phenomena

Battistoni

Xue

Som

2015

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

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-This work reports investigations on Diesel spray transients, accounting for internal nozzle flow and needle motion, and demonstrates how seamless calculations of internal flow and external jet can be accomplished in a Large-Eddy Simulation (LES) framework using an Eulerian mixture model. Sub-grid stresses are modeled with the Dynamic Structure (DS) model, a non-viscosity based oneequation LES model. Two problems are studied with high level of spatial and temporal resolution. The first one concerns an End-Of-Injection (EOI) case where gas ingestion, cavitation, and dribble formation are resolved. The second case is a Start-Of-Injection (SOI) simulation that aims at analyzing the effect of residual gas trapped inside the injector sac on spray penetration and rate of fuel injection. Simulation results are compared against experiments carried out at Argonne National Laboratory (ANL) using synchrotron X-ray. A mesh sensitivity analysis is conducted to assess the quality of the LES approach by evaluating the resolved turbulent kinetic energy budget and comparing the outcomes with a length-scale resolution index. LES of both EOI and SOI processes have been carried out on a single hole Diesel injector, providing insights in to the physics of the processes, with internal and external flow details, and linking the phenomena at the end of an injection event to those at the start of a new injection. Concerning the EOI, the model predicts ligament formation and gas ingestion, as observed experimentally, and the amount of residual gas in the nozzle sac matches with the available data. The fast dynamics of the process is described in detail. The simulation provides unique insights into the physics at the EOI. Similarly, the SOI simulation shows how gas is ejected first, and liquid fuel starts being injected with a delay. The simulation starts from a very low needle lift and is able to predict the actual Rate-Of-Injection (ROI) and jet penetration, based only on the prescribed needle motion. Finally, guidelines and future improvements of the model are discussed concerning the simulation of the transient injection phases.Résumé -Simulations aux grandes échelles (Large-Eddy Simulation, LES) de transitoires de jets liquides : phénomènes de début et fin d'injection -Le présent article rend compte d'études sur les transitoires de jets Diesel, prenant en compte l'écoulement interne de l'injecteur et le mouvement de l'aiguille, et démontre comment des calculs d'écoulement interne et de jet peuvent être réalisés dans le cadre d'une approche de type simulation aux grandes échelles (Large-Eddy Simulation, LES) en utilisant un modèle eulérien de mélange. Les contraintes sous-mailles sont modélisées avec un modèle de Structure Dynamique (Dynamic Structure, DS), un modèle LES à une équation non basé sur une viscosité turbulente. Deux problèmes sont étudiés avec un niveau élevé de résolution spatiale et temporelle. Le premier concerne un cas de fin d'injection (End-Of-Injection, EOI), où l'ingestion de gaz, la cavitation, et la for...

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“…In spite of its relative simplicity, this case is quite popular among engine CFD modelers [7,[10][11][12][39][40][41], because of its close resemblance to an actual engine intake flow. Figure 2a sketches the domain configuration, while Table 2 contains the dimensional parameters and flow conditions used for the simulations' setup.…”

Section: Fixed Intake Valvementioning

confidence: 99%

A Modified Version of the RNG k–ε Turbulence Model for the Scale-Resolving Simulation of Internal Combustion Engines

2017

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Abstract:The unsteady and random character of turbulent flow motion is a key aspect of the multidimensional modeling of internal combustion engines (ICEs). A typical example can be found in the prediction of the cycle-to-cycle variability (CCV) in modern, highly downsized gasoline direct injection (GDI) engines, which strongly depends on the accurate simulation of turbulent in-cylinder flow structures. The current standard for turbulence modeling in ICEs is still represented by the unsteady form of Reynold-averaged Navier Stokes equations (URANS), which allows the simulation of full engine cycles at relatively low computational costs. URANS-based methods, however, are only able to return a statistical description of turbulence, as the effects of all scales of motion are entirely modeled. Therefore, during the last decade, scale-resolving methods such as large eddy simulation (LES) or hybrid URANS/LES approaches are gaining increasing attention among the engine-modeling community. In the present paper, we propose a scale-resolving capable modification of the popular RNG k-ε URANS model. The modification is based on a detached-eddy simulation (DES) framework and allows one to explicitly set the behavior (URANS, DES or LES) of the model in different zones of the computational domain. The resulting zonal formulation has been tested on two reference test cases, comparing the numerical predictions with the available experimental data sets and with previous computational studies. Overall, the scale-resolved part of the computed flow has been found to be consistent with the expected flow physics, thus confirming the validity of the proposed simulation methodology.

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Boundary Conditions and SGS Models for LES of Wall-Bounded Separated Flows: An Application to Engine-Like Geometries

Cited by 17 publications

References 31 publications

Comparison of Direct and Large Eddy Simulations of the Turbulent Flow in a Valve/Piston Assembly

Comparison of Direct and Large Eddy Simulations of the Turbulent Flow in a Valve/Piston Assembly

Large-Eddy Simulation (LES) of Spray Transients: Start and End of Injection Phenomena

A Modified Version of the RNG k–ε Turbulence Model for the Scale-Resolving Simulation of Internal Combustion Engines

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