Index of Resolution Quality for Large Eddy Simulations

Çelik, İsmail; Cehreli, Zeynep N.; Yavuz, İbrahim

doi:10.1115/1.1990201

Cited by 542 publications

(352 citation statements)

References 22 publications

Supporting

Mentioning

345

Contrasting

Unclassified

Order By: Relevance

“…Here, is the resolved kinetic energy and is the total kinetic energy. The adequate values of _ for high Reynolds number flows are more than 0.75 [42]. The minimum _ in the current study was 0.91, confirming the adequacy of the number of cells.…”

Section: Grid Independency and Validationssupporting

confidence: 57%

On the dissipation and dispersion of entropy waves in heat transferring channel flows

2017

View full text Add to dashboard Cite

This paper investigates the hydrodynamic and heat transfer effects upon the dissipation and dispersion of entropy waves in non-reactive flows. These waves, as advected density inhomogeneities downstream of unsteady flames, may decay partially or totally before reaching the exit nozzle, where they are converted into sound. Attenuation of entropy waves dominates the significance of the subsequent acoustic noise generation.Yet, the extent of this decay process is currently a matter of contention and the pertinent mechanisms are still largely unexplored. To resolve this issue, a numerical study is carried out by compressible large eddy simulation (LES) of the wave advection in a channel subject to convective and adiabatic thermal boundary conditions. The dispersion, dissipation and spatial correlation of the wave are evaluated by post-processing of the numerical results. This includes application of the classical coherence function as well as development of nonlinear quantitative measures of wave dissipation and dispersion. The analyses reveal that the high frequency components of the entropy wave are always strongly damped. The survival of the low frequency components heavily depends upon the turbulence intensity and thermal boundary conditions of the channel. In general, high turbulence intensities and particularly heat transfer intensify the decay and destruction of the spatial coherence of entropy waves. In some cases, they can even result in the complete annihilation of the wave. The current work can therefore resolve the controversies arising over the previous studies of entropy waves with different thermal boundary conditions.

show abstract

Section: Grid Independency and Validationssupporting

confidence: 57%

On the dissipation and dispersion of entropy waves in heat transferring channel flows

2017

View full text Add to dashboard Cite

show abstract

“…In fact, the objective in LES is to generate an optimal mesh size within the Taylor microscale range allowing the capture of the most energetic turbulent structures (Ghosal, 1999;Celik et al, 2005). Otherwise, a classical grid independency would yield a DNS simulation altering the optimization approach of LES.…”

Section: Fig 2 Computational Gridmentioning

confidence: 99%

Flow Dynamics of a Plane Jet Impinging on a Slotted Plate: Large Eddy Simulation

Kharoua¹,

Khezzar²,

Alshehhi³

2017

JAFM

View full text Add to dashboard Cite

A turbulent plane jet impinging on a slotted surface is simulated using Large Eddy Simulation LES. The Reynolds number, based on the jet-exit velocity and width, is equal to 5435. The slotted surface is placed at a distance equal to four times the jet-exit width. Three computational grids were used to assess the accuracy of the LES simulations conducted. The interaction effects of the jet with the slot propagate away from the slot region and manifest into pressure perturbations. Interesting phenomena were observed when linking the dynamic flow features upstream and downstream of the slotted surface. LES predicted three dominant frequencies at different points from time signals of velocities and pressure. The dominant frequency of the pressure field, away from the slot, corresponds to that of coherent vortices which follow a trajectory that is far from being deviated towards the wall jet or into the slot of the impingement wall completely. Among these turbulent structures of interest, pairs of opposite, but in phase, vortices are responsible for promoting the occurrence of the throttling phenomenon. The characteristic frequencies of the pressure field are similar upstream and downstream of the impingement wall. The peaks of the fluctuating pressures, away from the slot, correlate well with the minimum flow rate through the slot which correspond to the throttling phenomenon.

show abstract

“…Determination of good or bad LES quality with a given resolution and numerical scheme has been extensively discussed in many studies [13,[38][39][40][41][42]. Focusing on engine simulations, some authors [12,37] have applied several LES quality indices [11,13].…”

Section: Les Quality Criteriamentioning

confidence: 99%

“…Focusing on engine simulations, some authors [12,37] have applied several LES quality indices [11,13]. These LES indices are used to estimate, whether a given resolution is sufficient for a "good LES".…”

Section: Les Quality Criteriamentioning

confidence: 99%

See 1 more Smart Citation

Investigation of Numerical Effects on the Flow and Combustion in LES of ICE

Nguyen

Kempf

2017

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

View full text Add to dashboard Cite

-This work investigates the influence of numerical dissipation on the modeled combustion in Large Eddy Simulations (LES). It is well known that capturing the dynamics of the in-cylinder flow is crucial for engine simulations, as it strongly affects flame propagation. The flame propagation during the power-stroke highly depends on the turbulence level that is developed throughout compression. This turbulence level will be strongly influenced by the accuracy of the numerical schemes employed. Even a small extent of upwinding, filtering, low-order implicit time-stepping, cell-stretching or mapping between grids may affect the flow field, the turbulence level, and hence the turbulent flame speed and the pressure curve. To provide a reference, the LES in-house code PsiPhi is used, which ensures a minimum of dissipation due to high order explicit time-stepping, homogeneous and isotropic filters and cells. Good stability of the code permits the use of a second-order Central Differencing Scheme (CDS) for the transport of momentum, avoiding numerical dissipation. To analyse the effect of numerical dissipation, simulations of a fired engine are performed using different numerical schemes for the convection of momentum. Physical quantities including the total kinetic energy, the velocity gradient, the turbulent viscosity, the in-cylinder pressure, the flame propagation or the burning rate of different test cases are evaluated and compared to each other to show the numerical effects on combustion. Furthermore, the suitability of common LES quality criteria including an energy criterion and viscosity ratio is discussed based on the comparison of simulations with less and more accurate numerics. It is shown that these LES quality indicators can be highly misleading.

show abstract

Index of Resolution Quality for Large Eddy Simulations

Cited by 542 publications

References 22 publications

On the dissipation and dispersion of entropy waves in heat transferring channel flows

On the dissipation and dispersion of entropy waves in heat transferring channel flows

Flow Dynamics of a Plane Jet Impinging on a Slotted Plate: Large Eddy Simulation

Investigation of Numerical Effects on the Flow and Combustion in LES of ICE

Contact Info

Product

Resources

About