The Concept of Tangential Stretching Rate in Reactive Systems and its Applications
10:45 - 11:15
Level 0 lecture hall between Al-Jazri and Al-Kindi (buildings 4 and 5)
The "stretching rate" is a measure of the dilation/contraction of the flow of a dynamical system. When the dynamical system describe the kinetics of a combustive mixture a positive/negative "stretching rate" characterizes the explosive/dissipative local nature of the reactive system. We combined the concepts of stretching rate with the decomposition of the local tangent space in eigen modes as done in the Computational Singular Perturbation methods to form a Tangential Stretching Rate (TSR) index.
The main feature of the TSR is its ability to identify unambiguously the most energetic scale at a given space location and time instant, both during the explosive and dissipative regimes. The TSR depends only on the local composition of the mixture, its temperature and pressure. As such, it can be readily computed during the post processing of spatially homogeneous reactive systems (ODEs problems). The TSR definition has been extended to cope with in-homogenous reactive flows (PDEs problems), where the transport terms (convection and diffusion) are accounted for on a local basis.
The talk will review the theoretical foundations of the TSR index, and will illustrate two recent applications of the TSR in relation with (i) the automatic generation of skeletal mechanisms with minimal user expertise, and (ii) the post-processing of DNS datasets of laminar and turbulent flows in view of detecting spontaneous ignition and deflagration fronts as well as the main cause-effect relations between driving processes (convection, diffusion, reactions) and the evolution of the state variable fields.