  Understanding the generation mechanism of the heating flux is essential for
the design of hypersonic vehicles. We proposed a novel formula to decompose the
heat flux coefficient into the contributions of different terms by integrating
the conservative equation of the total energy. The reliability of the formula
is well demonstrated by the direct numerical simulation results of a hypersonic
transitional boundary layer. Through this formula, the exact process of the
energy transport in the boundary layer can be explained and the dominant
contributors to the heat flux can be explored, which are beneficial for the
prediction of the heat and design of the thermal protection devices
