Nicolas Bourgeois (UCL)

Due to their highly non linear and very stiff behaviors, the systems of ODEs resulting from the chemical kinetics equations have to be solved using specific solvers that usually scales as O(N^2) with N the number of species of the kinetic mechanism.  Coupling CFD simulations to detailed kinetic mechanisms (i.e. with more than 1000 chemical species) is unaffordable in terms of CPU cost as such systems have to be solved in each cell. Reduction techniques have to be employed to tackle this problem. Such strategies act on two main aspects: first, the number of species can be dynamically decreased by selecting the deemed active species; the second option is to tabulate the results of previously computed solutions and to interpolate them in cells where conditions are assessed to be sufficiently similar. The TDAC (Tabulation of Dynamic Adaptive Chemistry) algorithm combines those two reduction techniques. In the present study, the low-compressible reactive RANS equations have been coupled to the TDAC algorithm and are solved using OpenFOAM. TDAC will also most probably be part of the next official release of OpenFOAM. Our current studies concern simulations of Rapid Compression Machines (RCM). A RCM is an experimental device dedicated to the investigation of auto-ignition phenomena. A reactive mixture is placed inside a reactive chamber that is rapidly compressed by a single-stroke piston that stops at top-dead-center, essentially reproducing the first part of the cycle of an internal combustion engine (compression followed by fuel ignition). A specific solver dedicated to RCM simulations has been developed, basically starting from the reactingFoam and engineFoam solvers available in the OpenFOAM library. Together with the TDAC algorithm, this solver allows us to obtain results that are the first to couple high fidelity CFD simulations to detailed chemistry in the context of RCM studies.