Incipient thermal choking and stable shock-train formation in the heat-release region of a scramjet combustor. Part II: Large eddy simulations

Larsson, Johan; Laurence, Stuart J.; Bermejo-Moreno, Iván; Bodart, Julien; Karl, Sebastian; Vicquelin, Ronan

doi:10.1016/j.combustflame.2014.09.017

Cited by 102 publications

(31 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The massively paralleled CharLES x , developed at Center for Turbulence Research, Stanford University, is used in this study as the finite-volume solver. CharLES x has been applied to studies of several different flow problems including aeroacoustics [21], supercritical flows [22], supersonic combustion [23], and aerodynamic flows [24]. A brief summary of the numerical schemes is provided here, and for more details the interested readers are referred to the work by Ham et al [25] and Khalighi et al [26].…”

Section: Finite-volume Discretizationmentioning

confidence: 99%

MVP-Workshop Contribution: Modeling of Volvo bluff body flame experiment

Peter

et al. 2017

55th AIAA Aerospace Sciences Meeting

View full text Add to dashboard Cite

The Volvo burner features the canonical configuration of a bluff-body stabilized premixed flame. This configuration was studied experimentally under the Volvo Flygmotor AB program. Two cases are considered in this study: a non-reacting case with an inlet flow speed of 16.6 m/s and a reacting case with equilibrium ratio of 0.65 and inflow speed of 17.3 m/s. The characteristic vortex shedding in the wake behind the bluff body is present in the non-reacting case, while two oscillation modes are intermittently present in the reacting case. A series of large-eddy simulations are performed on this configuration using two solvers, one using a high-resolution finite-volume (FV) scheme and the other featuring a high-order discontinuous-Galerkin (DG) discretization. The FV calculations are conducted on hexahedral meshes with three different resolution (4mm, 2mm, and 1mm). The DG calculations are performed using two different polynomial orders on the same tetrahedral mesh. For the non-reacting cases, good agreement with respect to the experimental data is achieved by both solvers at high numerical resolution. The reacting cases are calculated using a two-step global mechanism in combination with the thickened-flame model. Reasonable agreement with experiments is obtained by both solvers at higher resolution. Models for combustion-turbulence interaction are necessary for the reacting case as it contains the length scale of the flame, which is smaller than the grid resolution in all calculations. The impact of such models on the flame stability and flow/flame dynamics is the subject of future research.

show abstract

Section: Finite-volume Discretizationmentioning

confidence: 99%

MVP-Workshop Contribution: Modeling of Volvo bluff body flame experiment

Peter

et al. 2017

55th AIAA Aerospace Sciences Meeting

View full text Add to dashboard Cite

show abstract

“…The symmetry boundary condition is obviously an approximation to the physical combustor and carries implications for the overall fidelity that can be achieved. Despite this, it is a reasonable concession given the cost constraints and has been used in other investigations [25,26]. Simulations of the full HF2 domain (i.e., no Specific inflow boundary conditions of the isolator, primary injectors, and secondary injectors are shown in Table 1.…”

Section: Boundary Conditionsmentioning

confidence: 99%

Large eddy simulations of the HIFiRE scramjet using a compressible flamelet/progress variable approach

Saghafian

Shunn

Philips

et al. 2015

Proceedings of the Combustion Institute

View full text Add to dashboard Cite

In this study, large eddy simulations (LES) of supersonic combustion using a compressible flamelet/progress variable (CFPV) approach are performed for the HIFiRE scramjet at Mach 8 flight conditions. The LES results show good agreement with the ground test experimental measurements. The combustion model is based on an efficient flamelet approach, where compressibility corrections are devised based on assumed functional forms of important thermo-chemical quantities. Specifically, the source term of the progress variable is rescaled with the local density and temperature in the LES, leading to improved predictions relative to existing flamelet models. A modified equilibrium wall-model, capable of predicting the viscous heating, is used in the viscous near-wall region. Temperature near the wall increases significantly due to viscous heating, enhancing the reaction rate and heat-release. This is shown to be a crucial step for accurately predicting the pressure rise in the combustor.

show abstract

“…The unstructured LES-solver CharLES x is used in this study. This code has been extensively used for turbulent flow calculations [51,52,53,54,55,56]. A brief summary of the numerical schemes is provided here, and for more details the interested readers are referred to the work by Ham et al [57] and Khalighi et al [58].…”

Section: Mathematical Modelmentioning

confidence: 99%

Lyapunov exponent and Wasserstein metric as validation tools for assessing short-time dynamics and quantitative model evaluation of large-eddy simulation

Peter

et al. 2018

2018 AIAA Aerospace Sciences Meeting

View full text Add to dashboard Cite

and velocity. This data is obtained from various diagnostics techniques, including nonintrusive methods such as laser spectroscopy and particle image velocimetry, or intrusive techniques such as exhaustgas sampling or thermocouple measurements [7,8,9,10]. Instead of directly measuring physical quantities, they are typically inferred from measured signals, introducing several correction factors and uncertainties [11]. Depending on the experimental technique, these measurements are generated from single-point data, line measurements, line-of-sight absorption, or multidimensional imaging at acquisition rates ranging from single-shot to high-repetition rate measurements to resolve turbulent dynamics [12]. This data is commonly processed in the form of statistical results from Favre and Reynolds averaging, conditional data, probability density functions, and scatter data. However, the diversity of data, it makes it difficult to fully utilize this data for a complete model assessment.3. Dynamic description: LES is inherently unsteady and a dynamic measure is desirable to further characterize the LES quality in representing the dynamic content of a simulation. This is particularly relevant for flows that are inherently transient. The key observation is that turbulence is a deterministic chaotic phenomenon, which is characterized by an aperiodic long-term behavior exhibiting high sensitivity to the initial conditions. Different approaches exist to measure and characterize a chaotic solution [13,14,15,16,17]. On one hand, geometric approaches estimate the fractal dimension of the chaotic attractor, which, in turn, gives an estimate of the active degrees of freedom of the chaotic dynamical system. An accurate measure is the Hausdorff dimension [14], which is often approximated by box counting, based on phase-space partitioning and correlation dimension based on time series analysis [16]. On the other hand, dynamical approaches estimate the entropy content of the solution, namely the frequency with which a solution visits different regions of an attractor, for example by the Kolmogorov-Sinai entropy.The objective of this contribution is to introduce methods that enable the quantitative analysis of LES.The first metric introduces the Lyapunov exponent [18] as a metric for the assessment of the dynamic content of LES-calculations. Specifically, the Lyapunov exponent provides a measure of chaos in turbulent flows, and represents the rate of separation, and its reciprocal is closely related to the predictability horizon of a chaotic solution. In particular, the Lyapunov exponent, λ, is amenable to a simple physical interpretation:If a system is chaotic, given an infinitesimal initial perturbation to the solution, two trajectories of the system separate in time exponentially until nonlinear saturation. The average exponential separation is the Lyapunov exponent. A solution is typically regarded as being chaotic if there exists at least one positive Lyapunov exponent. The Lyapunov exponent is (i) a robust indicator of chaos, (ii)...

show abstract

Incipient thermal choking and stable shock-train formation in the heat-release region of a scramjet combustor. Part II: Large eddy simulations

Abstract: International audienc

Cited by 102 publications

References 32 publications

MVP-Workshop Contribution: Modeling of Volvo bluff body flame experiment

MVP-Workshop Contribution: Modeling of Volvo bluff body flame experiment

Large eddy simulations of the HIFiRE scramjet using a compressible flamelet/progress variable approach

Lyapunov exponent and Wasserstein metric as validation tools for assessing short-time dynamics and quantitative model evaluation of large-eddy simulation

Contact Info

Product

Resources

About