Direct numerical simulation of three-dimensional flame instabilities

The evolution of premixed gas flames near extinction and stability limits is of primary interest for many applications in combustion technology. Under such conditions the flames are very sensitive, and exhibit quasi-steady state behaviour so that they are well-suited to determine flammability limits. We show three-dimensional numerical simulation of the transient behaviour of lean H-2-air flames. The thermo-diffusive equations are solved by means of a parallelized Fourier-pseudospectral code. We compute the evolution of freely propagating spherical flames, whereby the influence of the initial flame radius is investigated. The results exhibit different behaviour as found in experimental studies under microgravity conditions, i.e. the splitting due to cellular instabilities, extinction, and stationary flame balls.