  The compressibility and heat of reaction influence on the scalar mixing in
decaying isotropic turbulence and homogeneous shear flow are examined via data
generated by direct numerical simulations (DNS). The reaction is modeled as
one-step, exothermic, irreversible and Arrhenius type. For the shear flow
simulations, the scalar dissipation rate, as well as the time scale ratio of
mechanical to scalar dissipation, are affected by compressibility and reaction.
This effect is explained by considering the transport equation for the
normalized mixture fraction gradient variance and the relative orientation
between the mixture fraction gradient and the eigenvectors of the solenoidal
strain rate tensor.
