The dependence on the lateral distance
to the center-plane and on time
of the average of the scalar dissipation rate
conditioned on the scalar
has been investigated in a temporally-evolving shear layer using a direct numerical simulation. As the inviscid scaling of the unconditional mean dissipation rate is approached, the conditional mean
follows also an approximate self-similar behavior within the time interval considered in the simulations and
shows two strong peaks at a distance of about one vorticity thickness from the center-plane, with dissipation values about 3 times the one in the central region. It is showed that this spatial variation is introduced by the nonturbulent/turbulent transition regions, which are identified by means of gradient trajectories of the scalar field.