This paper demonstrates that a Large Eddy Simulation (LES) combustion model based on tabulated chemistry and Eulerian stochastic fields can successfully describe the flame dynamics of a premixed turbulent swirl flame. The combustion chemistry is tabulated from one-dimensional burner-stabilized flamelet computations in dependence of progress variable and enthalpy. The progress variable allows to efficiently include a detailed reaction scheme, while the dependence on enthalpy describes the effect of heat losses on the reaction rate. The turbulence-chemistry interaction is modeled by eight Eulerian stochastic fields. A LES of a premixed swirl burner with a broadband velocity excitation is performed to investigate the flame dynamics, i.e. the response of heat release rate to upstream velocity perturbations. In particular, the flame impulse response and flame transfer function are identified from LES time series data. Simulation results for a range of power ratings are in good agreement with experimental data.
Digital rock analysis has proven to be useful for the prediction of petrophysical properties of conventional reservoirs, where the pore space is captured well by a modern µCT scanner with a resolution of 1-5 µm. Nevertheless, this resolution is not enough to accurately capture the pore space of tight (low-permeable) rock samples. As a result, derived digital rock models do not reflect the real rock topology, and permeability predictions yield unreliable results. Our approach deploys high-contrast µCT scanning technique and Focused Ion Beam milling combined with Scanning Electron Microscopy to improve the quality of digital rock models and, hence, the permeability prediction. This workflow is successfully applied to a low-permeable rock sample of Achimov deposits. The computed permeability compares well to the experimental value.
We quantify initial-data uncertainties on a shock accelerated heavy-gas cylinder by two-dimensional well-resolved direct numerical simulations. A high-resolution compressible multicomponent flow simulation model is coupled with a polynomial chaos expansion to propagate the initial-data uncertainties to the output quantities of interest. The initial flow configuration follows previous experimental and numerical works of the shock accelerated heavy-gas cylinder. We investigate three main initial-data uncertainties, (i) shock Mach number, (ii) contamination of SF6 with acetone, and (iii) initial deviations of the heavy-gas region from a perfect cylindrical shape. The impact of initial-data uncertainties on the mixing process is examined. The results suggest that the mixing process is highly sensitive to input variations of shock Mach number and acetone contamination. Additionally, our results indicate that the measured shock Mach number in the experiment of Tomkins et al. [“An experimental investigation of mixing mechanisms in shock-accelerated flow,” J. Fluid. Mech. 611, 131 (2008)] and the estimated contamination of the SF6 region with acetone [S. K. Shankar, S. Kawai, and S. K. Lele, “Two-dimensional viscous flow simulation of a shock accelerated heavy gas cylinder,” Phys. Fluids 23, 024102 (2011)] exhibit deviations from those that lead to best agreement between our simulations and the experiment in terms of overall flow evolution.
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