The approximate deconvolution model (ADM) for the large-eddy simulation of incompressible flows is detailed and applied to turbulent channel flow. With this approach an approximation of the unfiltered solution is obtained by repeated filtering. Given a good approximation of the unfiltered solution, the nonlinear terms of the filtered Navier–Stokes equations can be computed directly. The effect of nonrepresented scales is modeled by a relaxation regularization involving a secondary filter operation. Large-eddy simulations are performed for incompressible channel flow at Reynolds numbers based on the friction velocity and the channel half-width of Reτ=180 and Reτ=590. Both simulations compare well with direct numerical simulation (DNS) data and show a significant improvement over results obtained with classical subgrid scale models such as the standard or the dynamic Smagorinsky model. The computational cost of ADM is lower than that of dynamic models or the velocity estimation model.

An alternative approach to large-eddy simulation based on approximate deconvolution (ADM) is developed. The main ingredient is an approximation of the nonfiltered field by truncated series expansion of the inverse filter operator. A posteriori tests for decaying compressible isotropic turbulence show excellent agreement with direct numerical simulation. The computational overhead of ADM is similar to that of a scale-similarity model and considerably less than for dynamic models.

A formulation of the approximate deconvolution model (ADM) for the large-eddy simulation (LES) of compressible flows in complex geometries is detailed. The model is applied to supersonic compression ramp flow where shock-turbulence interaction occurs. With the ADM approach an approximation to the unfiltered solution is obtained from the filtered solution by a series expansion involving repeated filtering. Given a sufficiently good approximation of the unfiltered solution at a time instant, the flux terms of the underlying filtered transport equations can be computed directly, avoiding the need to explicitly compute subgrid-scale closures. The effect of nonrepresented scales is modeled by a relaxation regularization involving a secondary filter operation and a dynamically estimated relaxation parameter. Results of the large-eddy simulation of the turbulent supersonic boundary layer along a compression ramp compare well with filtered DNS data. The filtered shock solution is correctly predicted by the ADM procedure, demonstrating that turbulent and nonturbulent subgrid-scales are properly modeled. We found that a computationally expensive shock-capturing technique was not necessary for stable integration. As a consequence, the computational effort for simulations with ADM is approximately as large as for a coarse-grid DNS with a hybrid compact-upwind-ENO scheme, since the additional computational cost for the subgrid-scale model is more than compensated due to the fact that in the LES flux-derivatives can be computed by linear central finite differences on the entire domain.

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Propylene glycol and triacetin are chemical compounds, commonly used as food additives. Though the usage of the pure chemicals is not considered harmful when used as dietary supplements, little is known about the nature of their thermal degradation products and the impact they may have on human health. For these reasons, in this manuscript we investigate the thermal decomposition mechanisms of both neutral propylene glycol and triacetin in the gas phase by a novel simulation framework. This is based on a free energy sampling methodology followed by an accurate energy refinement. Structures, Gibbs free energy barriers, and rate constants at 800 K were computed for the different steps involved in the two pyrolytic processes. The thermal decomposition mechanisms found theoretically for propylene glycol and triacetin were validated by a qualitative experimental investigation using gas-phase chromatography-mass spectroscopy, with excellent agreement. The results provide a validation of the novel simulation framework and shed light on the potential hazard to the health that propylene glycol and triacetin may have when exposed to high temperatures.