Evaluation of Flame Area Based on Detailed Chemistry DNS of Premixed Turbulent Hydrogen-Air Flames in Different Regimes of Combustion

Precise evaluation of flame surface area plays a pivotal role in the fundamental understanding and accurate modelling of turbulent premixed flames. This necessity is reflected in the requirement for the instantaneous flame area evaluation of the turbulent burning velocity (by making use of Damköhler’s first hypothesis). Moreover, the information regarding flame area is required in the context of flame surface density based modelling, and for determining the wrinkling factor or estimating the efficiency function. Usually flame surface areas in experiments and Direct Numerical Simulation (DNS) analyses are evaluated differently and the present analysis aims at comparing these approaches by making use of a detailed chemistry DNS database of turbulent, statistically planar flames. It has been found that the flame surface area evaluation is sensitive to the choice of scalar quantity and the isosurface level, and this holds particularly true for two-dimensional evaluations. The conditions, which provide a satisfactory agreement between experimental and numerical approaches in the flame area evaluation, have been identified by a detailed comparative analysis of the usual postprocessing techniques.