  We perform a computationl study of front speeds of G-equation models in time
dependent cellular flows. The G-equations arise in premixed turbulent
combustion, and are Hamilton-Jacobi type level set partial differential
equations (PDEs). The curvature-strain G equations are also non-convex with
degenerate diffusion. The computation is based on monotone finite difference
discretization and weighted essentially nonoscillatory (WENO) methods. We found
that the large time front speeds lock into the frequency of time periodic
cellular flows in curvature-strain G-equations similar to what occurs in the
basic inviscid G-equation. However, such frequency locking phenomenon
disappears in viscous G-equation, and in the inviscid G-equation if time
periodic oscillation of the cellular flow is replaced by time stochastic
oscillation.
