Initial-value ordinary differential equation solution via variable order Adams method (SIVA/DIVA) package is collection of subroutines for solution of nonstiff ordinary differential equations. There are versions for single-precision and double-precision arithmetic. Requires fewer evaluations of derivatives than other variable-order Adams predictor/ corrector methods. Option for direct integration of second-order equations makes integration of trajectory problems significantly more efficient. Written in FORTRAN 77.

Solving Ordinary Differential Equations

Rayleigh–Taylor and Richtmyer-Meshkov instability induced flow, turbulence, and mixing. II

https://hal.archives-ouvertes.fr/hal-00803230/document

Large Eddy Simulations of gaseous flames in gas turbine combustion chambers

We review numerical methods for direct numerical simulation (DNS) and large-eddy simulation (LES) of turbulent compressible flow in the presence of shock waves. Ideal numerical methods should be accurate and free from numerical dissipation in smooth parts of the flow, and at the same time they must robustly capture shock waves without significant Gibbs ringing, which may lead to nonlinear instability. Adapting to these conflicting goals leads to the design of strongly nonlinear numerical schemes that depend on the geometrical properties of the solution. For low-dissipation methods for smooth flows, numerical stability can be based on physical conservation principles for kinetic energy and/or entropy. Shock-capturing requires the addition of artificial dissipation, in more or less explicit form, as a surrogate for physical viscosity, to obtain nonoscillatory transitions. Methods suitable for both smooth and shocked flows are discussed, and the potential for hybridization is highlighted. Examples of the application of advanced algorithms to DNS/LES of turbulent, compressible flows are presented.

Numerical Methods for High-Speed Flows

Direct numerical simulation of a three-dimensional spatially developing turbulent slot-burner Bunsen flame has been performed with a new reduced methane–air mechanism. The mechanism, derived from sequential application of directed relation graph theory, sensitivity analysis and computational singular perturbation over the GRI-1.2 detailed mechanism is non-stiff and tailored to the lean conditions of the DNS. The simulation is performed for three flow through times, long enough to achieve statistical stationarity. The turbulence parameters have been chosen such that the combustion occurs in the thin reaction zones regime of premixed combustion. The data is analyzed to study possible influences of turbulence on the structure of the preheat and reaction zones. The results show that the mean thickness of the turbulent flame, based on progress variable gradient, is greater than the corresponding laminar flame. The effects of flow straining and flame front curvature on the mean flame thickness are quantified through conditional means of the thickness and by examining the balance equation for the evolution of the flame thickness. Finally, conditional mean reaction rate of key species compared to the laminar reaction rate profiles show that there is no significant perturbation of the heat release layer.

Structure of a spatially developing turbulent lean methane–air Bunsen flame

Approximating the chemical structure of partially premixed and diffusion counterflow flames using FPI flamelet tabulation

Many models are now available to describe chemistry at a low CPU cost, but only a few of them can be used to describe correctly premixed, partially premixed and diffusion combustion. One of them is the FPI model that uses two coordinates: the mixture fraction Z and the progress variable c. In this paper, we introduce a new evolution of the FPI method that can now handle heat losses. After a short review of kinetic models used in turbulent combustion, the main features of the new three-dimensional FPI method, in which we introduce a third coordinate for enthalpy h, are presented. First, a one-dimensional radiative premixed flame validation case is presented for a large range of radiative heat losses. Second, we present the results of simulations of two laminar burners. Both the fully and the partially premixed burner simulations give a good estimation of all the flame features such as the flame stabilization (driven by heat losses), the flame structure and the profile of major and minor species.

Modelling non-adiabatic partially premixed flames using flame-prolongation of ILDM

https://hal.archives-ouvertes.fr/hal-00472611/document

A filtered tabulated chemistry model for LES of premixed combustion

Effects of water vapor addition on the laminar burning velocity of oxygen-enriched methane flames

Tabulated chemistry and presumed probability density function (PDF) approaches are combined to perform RANS modeling of premixed turbulent combustion. The chemistry is tabulated from premixed flamelets with three independent parameters: the equivalence ratio of the mixture, the progress of reaction, and the specific enthalpy, to account for heat losses at walls. Mean quantities are estimated from presumed PDFs. This approach is used to numerically predict a turbulent premixed flame diluted by hot burnt products at an equivalence ratio that differs from the main stream of reactants. The investigated flame, subjected to high velocity fluctuations, has a thickened-wrinkled structure. A recently proposed closure for scalar dissipation rate that includes an estimation of the coupling between flame wrinkling and micromixing is retained. Comparisons of simulations with experimental measurements of mean velocity, temperature, and reactants are performed.

Benoit Fiorina

Papers

Approximating the chemical structure of partially premixed and diffusion counterflow flames using FPI flamelet tabulation

Modelling non-adiabatic partially premixed flames using flame-prolongation of ILDM

A filtered tabulated chemistry model for LES of premixed combustion

Effects of water vapor addition on the laminar burning velocity of oxygen-enriched methane flames

Premixed turbulent combustion modeling using tabulated detailed chemistry and PDF