Direct numerical simulation of a reacting turbulent channel flow with thermochemical ablation

Cabrit, Olivier; Nicoud, Franck

doi:10.1080/14685248.2010.522578

Cited by 3 publications

(2 citation statements)

References 48 publications

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“…Reproducing exactly the same condition with the numerical simulation was not possible with the computational resources available. For this reason, a strategy similar to the one proposed by Cabrit & Nicoud 45 was used, which consisted of performing an ensemble average over different simulations whose initial solutions were different. In this way, each numerical simulation could be limited to a simulation-time of 10 ms, without simulating the 1000 ms between each pulsation.…”

Section: Simulation Strategymentioning

confidence: 99%

Assessment of subgrid-scale models with a large-eddy simulation-dedicated experimental database: The pulsatile impinging jet in turbulent cross-flow

et al. 2014

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of subgrid-scale models with an LES-dedicated experimental database: the pulsatile impinging jet in turbulent cross-flow.1 Large-Eddy Simulation (LES) in complex geometries and industrial applications like piston engines, gas turbines or aircraft engines requires the use of advanced subgridscale (SGS) models able to take into account the main flow features and the turbulence anisotropy. Keeping this goal in mind, this paper reports an LES-dedicated experiment of a pulsatile hot-jet impinging a flat-plate in the presence of a cold turbulent cross-flow. Unlike commonly used academic test cases, this configuration involves different flow features encountered in complex configurations: shear/rotating regions, stagnation point, wall-turbulence, and the propagation of a vortex ring along the wall. This experiment was also designed with the aim to use quantitative and nonintrusive optical diagnostics such as Particle Image Velocimetry (PIV), and to easily perform an LES involving a relatively simple geometry and well-controlled boundary conditions. Hence, two eddy-viscosity-based SGS models are investigated: the dynamic Smagorinsky model 1 and the σ-model 2 . Both models give similar results during the first phase of the experiment. However, it was found that the dynamic Smagorinsky model could not accurately predict the vortex-ring propagation, while the σ-model provides a better agreement with the experimental measurements. Setting aside the implementation of the dynamic procedure (implemented here in its simplest form,i.e. without averaging over homogeneous directions and with clipping of negative values to ensure numerical stability), it is suggested that the mitigated predictions of the dynamic Smagorinsky model are due to the dynamic constant, which strongly depends on the mesh resolution. Indeed, the shear-stress near the wall increases during the vortex-ring impingement leading to a less refined mesh in terms of wall units, y + . This loss of resolution induces a poor damping of the dynamic constant, which is no longer able to adjust itself to ensure the expected y 3 -behaviour near the wall. It is shown that the dynamic constant is never small enough to properly balance the large values of the squared magnitude of the strain-rate tensor, 2S ij S ij . The experimental database is made available to the community upon request to the authors.

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Section: Simulation Strategymentioning

confidence: 99%

Assessment of subgrid-scale models with a large-eddy simulation-dedicated experimental database: The pulsatile impinging jet in turbulent cross-flow

et al. 2014

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“…Eq. (13) corresponds to the boundary condition for species mass fractions and constitutes a non-linear system of equations which is solved thanks to an iterative method [36,37]…”

Section: Accounting For Surface Chemistry Through Boundary Conditionsmentioning

confidence: 99%

Direct Numerical Simulation of combustion near a carbonaceous surface in a quiescent flow

Chabane

Truffin

Nicolle

et al. 2015

International Journal of Heat and Mass Transfer

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In this work, unsteady gasification and oxidation of carbonaceous materials with gas-phase combustion under oxy-combustion conditions is studied. An original analytical solution is derived to validate the numerical species boundary condition for the heterogeneous surface reactions with frozen gas-phase. Direct Numerical Simulations accounting for multi-species diffusion and detailed chemistry with both species and energy boundary conditions taking into account the Stefan flux were subsequently performed to study combustion near a carbonaceous wall. Transition from gasification to solid carbon oxidation and gas-phase ignition is evidenced. The competition between homogeneous and heterogeneous reactions is discussed based on the analysis of the time-dependent surface and gas-phase species consumption and production rates. Transient histories of surface species as well as spatial profiles of gas-phase species, heat release and temperature are presented for two identified structures of gas-phase CO/O 2 reaction zone. In order to quantify the error induced by the Hirschfelder & Curtiss approximation for the multi-species diffusion and to evaluate the importance of the Dufour and Soret terms, a library dedicated to the computation of complex diffusion phenomena has been used to rebuild a priori, species and Soret fluxes for mass diffusion as well as Fourier, species and Dufour diffusion heat fluxes. Eventually, characteristic times of gas and surface reactions and those corresponding to the switch between the two structures of the gas-phase reaction zone are obtained over a wide range of initial O 2 /CO 2 concentrations.

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A Dedicated Les Experimental Database for the Assessment of Les SGS Models: The Pulsatile Jet Impingement in Turbulent Cross Flow

Toda

Cabrit

Truffin

et al. 2013

Proceeding of Eighth International Symposium on Turbulence and Shear Flow Phenomena

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Direct numerical simulation of a reacting turbulent channel flow with thermochemical ablation

Cited by 3 publications

References 48 publications

Assessment of subgrid-scale models with a large-eddy simulation-dedicated experimental database: The pulsatile impinging jet in turbulent cross-flow

Assessment of subgrid-scale models with a large-eddy simulation-dedicated experimental database: The pulsatile impinging jet in turbulent cross-flow

Direct Numerical Simulation of combustion near a carbonaceous surface in a quiescent flow

A Dedicated Les Experimental Database for the Assessment of Les SGS Models: The Pulsatile Jet Impingement in Turbulent Cross Flow

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