Reverse jet parameters study on aerodynamic thermal uncertainty of a blunt body

Adding head opposing jets is a common flow control approach to reduce the aerodynamic heating of hypersonic vehicles with blunt-shape head. However, interests of present studies are mostly focused on surface heating reduction originate from opposing jets only on single-and-determinate free incoming conditions, rather than that under existence of freestream perturbations, to the best of knowledge. In this work, two-layers research structure is formed to investigate the jet design parameters on surface thermal uncertainty with occurrence of free incoming perturbations. In the inner layer, the Polynomial Chaos method is applied for quantifying the surface thermal uncertainty, including the mean value and the standard deviation, under free incoming perturbations. In the outer layer, the Variance Analysis method is employed to describe the jet geometry and flow parameters on surface thermal uncertainty. As a consequence, the parameters impact on the mean surface heating under perturbations are found similar to that in baseline freestream condition. Moreover, only jet entry diameter and total-pressure ratio of jet-to-freestream are important when it comes to the standard deviation of surface heating. This research is anticipated to be available of robust thermal-reduction optimization on hypersonic vehicles with blunt-shape head in a wide range of free incoming conditions for reference.