Isotropic burn test problem for two different initial conditions—perturbed sphere (left) and sphere (right). Each of the contours marks the X( ¹²C) = 0.45 isocontours at t = 0, 0.01, and 0.02 s, with the initial conditions being the central contour. The spacing between contours is consistent with the laminar speed used to move the flame, v _l = 76 km s ⁻¹.