DNS study of the bending effect due to smoothing mechanism

Propagation of either an infinitely thin interface or a reaction wave of a nonzero thickness in forced, constant-density, statistically stationary, homogeneous, isotropic turbulence is simulated by solving unsteady 3D Navier-Stokes equations and either a level set (G) or a reaction-diffusion equation, respectively, with all other things being equal. In the case of the interface, the fully developed bulk consumption velocity normalized using the laminar-wave speed S _L depends linearly on the normalized rms velocity u ⁰ /S _L . In the case of the reaction wave of a nonzero thickness, dependencies of the normalized bulk consumption velocity on u ⁰ /S _L show bending, with the effect being increased by a ratio of the laminar-wave thickness to the turbulence length scale. The obtained bending effect is controlled by a decrease in the rate of an increase δA _F in the reaction-zone-surface area with increasing u ⁰ /S _L . In its turn, the bending of the δA _F (u ⁰ /S _L )-curves stems from inefficiency of small-scale turbulent eddies in wrinkling the reaction-zone surface, because such small-scale wrinkles characterized by a high local curvature are smoothed out by molecular transport within the reaction wave.