Advanced Basic State and Stability Analysis of Complex Hypersonic Geometries

Abstract

As the design of aerospace vehicles continues to evolve and become more complex, an accurate understanding of the physics at work in the flowfields around these vehicles is required. Alongside flight tests and wind tunnel experiments, computational fluid dynamics (CFD) is a cornerstone of modern aerospace design, and one facet of this field is understanding the process of laminar-to-turbulent flow transition. In conjunction with experiments, CFD can be used to model the laminar-to-turbulent transition process and better understand the underlying flow physics seen in wind tunnel experiments and flight tests. This work is focused on characterizing the flowfields of a set of hypersonic geometries and also determining the instability mechanisms that are most likely to cause transition using the parabolized stability equations. This work furthers the current state of the art by a) using modern stability analysis techniques to examine the instabilities present on complex hypersonic geometries and b) analyzing the sensitivity of these instability mechanisms to changes in geometry and to changes in vehicle conditions.

In particular, the Boundary-Layer Transition (BOLT) and Boundary-Layer Turbulence (BOLT-II) geometries will be studied, both at full scale and at wind-tunnel scale. Comparisons using basic state quantities will be made to experiments and other computations in order to provide validation and verification where possible. In addition, stability analyses will be performed in order to find the most amplified instability mechanisms for these geometries. Furthermore, a cone with a single slender fin (the Purdue Fin Cone) will also be studied. Both basic state quantities and stability analysis results will be compared to experiments run in the Boeing-AFOSR Mach 6 Quiet Tunnel (BAM6QT) at Purdue University in order to help investigate phenomena seen in wind tunnel tests. Overall, this work strives to provide insight to future stability analysis work ranging from computations to wind tunnel tests to flight tests.