  The decompositions of the skin-friction and heat transfer coefficients based
on the two-fold repeated integration in hypersonic transitional and turbulent
boundary layers are analyzed to explain the generations of the wall skin
friction and heat transfer. The Reynolds analogy factor slightly increases as
the wall temperature decreases, especially for the extremely cooled wall. The
integral analysis is applied to explain the overshoot behaviours of the
skin-friction and heat transfer coefficients in hypersonic transitional
boundary layers. The overshoot of the skin-friction coefficient is mainly
caused by the drastic change of the mean velocity profiles, and the overshoot
of the heat transfer coefficient is primarily due to the viscous dissipation.
In the hypersonic turbulent boundary layers, the skin-friction and heat
transfer coefficients increase significantly as the wall temperature decreases.
The effects of the mean velocity gradients and the Reynolds shear stress
contribute dominantly to the wall skin friction, and have weak correlations
with the wall temperature, except for the strongly cooled wall condition. The
strongly cooled wall condition and high Mach number can enhance the effect of
the Reynolds shear stress, and weaken the impact of the mean velocity
gradients. Furthermore, the magnitudes of the dominant relative contributions
of the mean temperature gradients, pressure dilatation, viscous dissipation and
the Reynolds heat flux to the heat transfer coefficient increase as the wall
temperature increases in the hypersonic turbulent boundary layers.
