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Publications (23)
Hybrid turbulence models that can accurately reproduce unsteady three-dimensional flow physics across the entire range of grid scales and turbulence dynamics from Reynolds-averaged Navier–Stokes (RANS), through large-eddy simulation (LES), down to direct numerical simulations (DNS) are of increasing interest to the turbulence modeling community. Ho...
A Lagrangian analysis approach is used to examine the effects of heat release on the dynamics of the enstrophy during highly turbulent premixed combustion. The analysis is performed using data from a direct numerical simulation of a statistically planar premixed methane–air flame at a Karlovitz number of 100. Through cumulative, conditional, and co...
There is a substantial need to better understand multi-physics interactions in realistic laboratory experiments, yet it is currently unfeasible to perform direct numerical simulations (DNS) of most such problems. As a result, reduced-order models such as those used to represent unclosed subgrid-scale stresses in large-eddy simulations (LES) and adv...
Autonomic closure for large eddy simulations (LES) replaces traditional prescribed subgrid models with an adaptive self-optimizing closure that solves a local, nonlinear, non-parametric system identification problem for each subgrid term, potentially at every point and time in the simulation. This can be regarded as a type of dynamic closure based...
Turbulent mixing is a physical process of fundamental importance in high-speed premixed flames. This mixing results in enhanced transport of temperature and chemical scalars, leading to potentially large changes in flame structure and dynamics. To understand turbulent mixing in non-reacting flows, a number of classical theories have been proposed t...
Turbulent mixing is a physical process of fundamental importance in high-speed premixed flames. This mixing results in enhanced transport of temperature and chemical scalars, leading to potentially large changes in flame structure and dynamics. To understand turbulent mixing in non-reacting flows, a number of classical theories have been proposed t...
We use approximate Bayesian computation (ABC) combined with an "improved" Markov chain Monte Carlo (IMCMC) method to estimate posterior distributions of model parameters in subgrid-scale (SGS) closures for large eddy simulations (LES) of turbulent flows. The ABC-IMCMC approach avoids the need to directly compute a likelihood function during the par...
Theory and computations have established that thermodynamic gradients created by hot spots in reactive gas mixtures can lead to spontaneous detonation initiation. However, the current laminar theory of the temperature-gradient mechanism for detonation initiation is restricted to idealized physical configurations. Thus, it only predicts conditions f...
Theory and computations have established that thermodynamic gradients created by hot spots in reactive gas mixtures can lead to spontaneous detonation initiation. However, the current laminar theory of the temperature-gradient mechanism for detonation initiation is restricted to idealized physical configurations. Thus, it only predicts conditions f...
A three-dimensional wavelet multi-resolution analysis of direct numerical simulations of a turbulent premixed flame is performed in order to investigate the spatially localized spectral transfer of kinetic energy across scales in the vicinity of the flame front. A formulation is developed that addresses the compressible spectral dynamics of the kin...
A new scale-sensitive physical-space conditional analysis is outlined and used to examine the scaling and collapse of velocity structure functions in turbulent premixed flames. The conditioning is based on local instantaneous temperatures in the premixed flame, and structure function scaling and collapse are examined using Kolmogorov-type dimension...
A Lagrangian analysis approach is used to examine the effects of high-speed turbulence on thermochemical trajectories in unconfined, stoichiometric hydrogen–air (H2–air) premixed flames. Two different intensities of turbulence in the unburnt reactants are considered, giving premixed flames with Karlovitz numbers of roughly 150 and 450. These two ca...
Multi-scale interactions and kinetic-energy transfer between turbulence and flames are fundamental to understanding and modeling premixed turbulent reacting flows. In order to investigate these phenomena, direct numerical simulations of a turbulent premixed flame are analyzed in this study. The results reveal a flux of kinetic energy that involves...
Spectral kinetic energy transfer by advective processes in turbulent premixed reacting flows is examined using data from a direct numerical simulation of a statistically planar turbulent premixed flame. Two-dimensional turbulence kinetic-energy spectra conditioned on the planar-averaged reactant mass fraction are computed through the flame brush an...
Subsonic and low-supersonic propulsion systems based on detonation waves have the potential to substantially improve efficiency and power density compared to traditional engines. Numerous technical challenges remain to be solved in such systems, however, including obtaining more efficient injection and mixing of air and fuels, more reliable detonat...
