Fluid dynamics beyond the continuum: A physical perspective on large-eddy simulation

High altitude relight is a matter of increasing importance for aero engine manufacturers, in which combustion plays literally a vital role. In this paper we want to evaluate the predictive capability of a combined Smoothed Particle Hydrodynamics (SPH) and Large Eddy Simulation with Conditional Moment Closure (LES-CMC) approach for a spray combustion process at these extreme conditions. The focus is on the SPH modelling of the kerosene primary atomization, the extraction of realistic spray boundary conditions for LES-CMC and the effect of the spray on combustion. Interestingly, it will be demonstrated that the fragment size distributions resulting from the airblast atomization are characterized by bimodal behaviour during the relight process and that small and large fragments differ significantly in their dynamical behavior. This is shown to affect the combustion in the Central Recirculation Zone (CRZ). Very large fragments are even able to supersede the flame from the CRZ, such that endothermic pyrolysis becomes dominant, but simultaneously essential to sustain and stabilize the remaining flame with reactive pyrolysis species. The study proves the ability of our methodology for extreme operating conditions, in which experimental insights are hardly possible.

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A Numerical Study of Aero Engine Sub-idle Operation: From a Realistic Representation of Spray Injection to Detailed Chemistry LES-CMC

Okraschevski

Mesquita

Koch

et al. 2023

Flow Turbulence Combust

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Characterization of flow-blurring atomization with Smoothed Particle Hydrodynamics (SPH)

Ates

Gundogdu

Okraschevski

et al. 2023

International Journal of Multiphase Flow

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Smoothed particle hydrodynamics physically reconsidered: The relation to explicit large eddy simulation and the issue of particle duality

et al. 2022

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In this work, we will identify a novel relation between Smoothed Particle Hydrodynamics (SPH) and explicit large eddy simulation using a coarse-graining method from non-equilibrium molecular dynamics. While the current literature points at the conclusion that characteristic SPH issues become restrictive for subsonic turbulent flows, we see the potential to mitigate these SPH issues by explicit subfilter stress modeling. We verify our theory by various simulations of homogeneous, isotropic turbulence at [Formula: see text] and compare the results to a direct numerical simulation [T. Dairay et al., “Numerical dissipation vs subgrid-scale modelling for large eddy simulation,” J. Comput. Phys. 337, 252–274 (2017)]. Although the simulations substantiate our theory, we see another issue arising, which is conceptually rooted in the particle itself, termed as particle duality. Finally, we conclude our work by acknowledging SPH as a coarse-graining method for turbulent flows, highlighting its capabilities and limitations.

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Fluid dynamics beyond the continuum: A physical perspective on large-eddy simulation

Cited by 3 publications

References 18 publications

A Numerical Study of Aero Engine Sub-idle Operation: From a Realistic Representation of Spray Injection to Detailed Chemistry LES-CMC

A Numerical Study of Aero Engine Sub-idle Operation: From a Realistic Representation of Spray Injection to Detailed Chemistry LES-CMC

Characterization of flow-blurring atomization with Smoothed Particle Hydrodynamics (SPH)

Smoothed particle hydrodynamics physically reconsidered: The relation to explicit large eddy simulation and the issue of particle duality

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