23 rd ICDERS July 24–29, 2011 Irvine, USA A Numerical Study of the Markstein Hypothesis in Finite Thickness Flames with Realistic Chemistry Nadeem A. Malik King Fahd University of Petroleum and Minerals, Department of Mathematics and Statistics P.O. Box 5046, Dhahran 31261, Kingdom of Saudi Arabia 1 Introduction Markstein’s hypothesis for the burning velocity of stretched laminar flames characterizes the effect of local heat release of a propagating flame on variations in the surface area along the flame front and the associated local flame curvature. However the general validity of Markstein.s theory is still debated in the combustion community; of special interest is whether this hypothesis is valid under conditions of realistic chemistry in finite thickness flames. The need to describe reacting systems with realistic chemistry has been recognised in a number of recent studies, [1, 2, 3]. One of the main drivers behind this trend relates to the energy and environmental sectors; restrictions on emissions of greenhouse gases, NOX, soot and other hazaradous substances to lower and lower levels places greater demands on the development of new fuels and on the optimisation of devices such as automotive engines and gas turbines. This in turn places greater demands on the accuracy of predictive simulations which must now include realistic chemistry. A critical issue, therefore, in the computational study of combustion and reacting flow systems is the capability of coupling of the unsteady compressible flow to the detailed chemistry and transport proper- ties. The recent progress in numerical software and in computer technology now offers the possibility to meet these demands, and implicit methods in particular have been receiving some attention due to their greater stability, although at the cost of large memory requirements [3, 4]. In [3] an implicit combus- tion code TARDIS(Transient Advection Reaction Diffusion Implicit Simulations) was developed which features the coupling of the fully compressible flow to the comprehensive chemical mechanisms. The method can resolve all the convective and chemical length and time scales present in stiff chemically reacting systems. In this study, TARDIS is used to investigate the Markstein hypothesis in premixed hydrogen/air and methane/air flames at atmospheric pressure. The flame stretch rate κ is the relative rate of change of an infinitesimal surface area A(t) surrounding a point on the surface of a flame, κ = 1 A dA dt (1) from which the non-dimensional Karlovich number Ka is defined, Ka = κt c (2) Correspondence to: namalik@kfupm.edu.sa (Permanent: n.malik@tsfirst.com) 1