Body-force effect on the lateral movement of cellular flames at low Lewis numbers - art. no. 026303

The body-force effect on the lateral movement of cellular flames is studied by unsteady calculations of reactive flows at low Lewis numbers. We employ the compressible Navier-Stokes equation including chemical reaction to tak e account of the hydrodynamic effect caused by thermal expansion. A sinusoi dal disturbance with the linearly most unstable wavelength is superimposed on a plane flame to simulate the formation of a cellular flame. The superim posed disturbance grows initially with time, and then the flame front chang es from a sinusoidal to a cellular shape. After the cell formation, the cel lular flame moves laterally at Lewis numbers lower than unity. The reason i s that the diffusive-thermal effect, and the nonlinear effect of the flame front, play a primary role in the appearance of the lateral movement of cel ls. The body-force effect has a great influence on the lateral velocity of cells. When flames are propagated upward, the lateral velocity decreases as the acceleration increases, even though the body-force effect has a destab ilizing influence. When flames are propagated downward, on the other hand, the lateral velocity takes a maximum value at the specific acceleration and decreases with an increase in acceleration. The dependence of lateral velo city on the acceleration is due to the augmentation and diminution in maxim um flame temperature and to the broadness and narrowness of a high-temperat ure region behind a convex flame front.