Investigation on applicability of multicomponent mass diffusion models in hypersonic boundary layer

In hypersonic flight, high-temperature thermochemical reactions make accurate modeling of mass-diffusion heat flux essential for reliable surface heat-flux prediction and thermal protection design. The accuracy and applicability of six approximate mass-diffusion models are systematically assessed against the classic Stefan–Maxwell formulation, which serves as the benchmark owing to its superior accuracy. The physical origins of the heat-flux deviations are further analyzed based on the intrinsic characteristics of each model. The results confirm that, for typical hypersonic cylindrical configurations, the classical binary scaling method can be effectively applied to analyze wall heat flux of varying radii. By incorporating the characteristics of the wall heat-flux distribution, a mapping relation is established that converts the heat-flux analysis from geometries of different scales to the stagnation-point heat flux of a reference configuration. Deviations from the approximate models occur not only in the case of diffusive heat flux but also indirectly in the conductive component. The magnitude of deviation generally increases with Mach number and decreases with altitude, with the primary physical source identified as the atomic oxygen diffusion flux deviation near the wall. This work provides practical criteria to select suitable diffusion models by jointly considering accuracy and computational efficiency.