Numerical research has been conducted to investigate the effects of two shortening methods, i.e., leading-edge truncation and axial contraction (stunting), on the startability and flowfields of the Busemann intakes in scramjet operation at Mach 8. The following insights have been gained from the observation of the local startability index variations of steady flowfields: (a) The Kantrowitz position for spontaneous starting is negligibly affected by viscosity, suggesting that shock wave / boundary layer interactions are primarily responsible for the difficulty in intake starting rather than the boundary layer displacement, (b) The Kantrowitz position relative to the intake leading edge moves upstream more distinctly in truncation, suggesting that truncated intakes should require slightly less effort to start than stunted ones with the same length reduction and entrance area. This can be attributed, in particular, to a decrease in the contraction of the intake due to truncation.
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