Numerical simulation of body-force effect on hydrodynamic flame stability.

Abstract

Unsteady motions of two-dimensional reactive flows have been simulated to investigate the body-force effect on hydrodynamic flame instability. The numerical model contains compressibility, viscosity, heat conduction, molecular diffusion, chemical reaction, and convection. We have calculated the evolution of a disturbed flame and numerically reproduced that the disturbance on the flame grows exponentially in time, as predicted by the linear theory. The growth rate of disturbance depending on its wave number was obtained and the critical wave number for neutral stability was determined. The disturbances having small wave number rather than the critical one are unstable: i.e., long wave disturbances are unstable. The body-force has great influence on the flame instability: the growth rate of disturbance increases and the unstable region becomes wide for body-force in the direction of the hot burned gas, and the growth rate decreases and the unstable region becomes narrow for the other case. Moreover, the cellular structure of the flame front as observed in the experiment is reproduced in the simulation.