  We investigate the effects of viscosity and heat conduction on the onset and
growth of Kelvin-Helmholtz instability (KHI) via an efficient discrete
Boltzmann model. Technically, two effective approaches are presented to
quantitatively analyze and understand the configurations and kinetic processes.
One is to determine the thickness of mixing layers through tracking the
distributions and evolutions of the thermodynamic nonequilibrium (TNE)
measures; the other is to evaluate the growth rate of KHI from the slopes of
morphological functionals. Physically, it is found that the time histories of
width of mixing layer, TNE intensity, and boundary length show high correlation
and attain their maxima simultaneously. The viscosity effects are twofold,
stabilize the KHI, and enhance both the local and global TNE intensities.
Contrary to the monotonically inhibiting effects of viscosity, the heat
conduction effects firstly refrain then enhance the evolution afterwards. The
physical reasons are analyzed and presented.
