This paper presents a new numerical method for investigating the relationship between cone nosetip bluntness on boundary layer transition in hypersonic flows. For years, Linear Stability Theory (LST) and the Parabolized Stability Equations (PSE) have provided the tools for analysis and prediction of laminar to turbulent transition for plates, sharp cones, and geometries for which the parallel or slowly-varying boundary layer assumptions are valid. Experiments on blunt cones have demonstrated that small nose bluntness radii delay transition, but when the bluntness reaches some critical value, the trend sharply reverses. It is difficult for LST and PSE to represent complex physics near blunt cone tips, including a curved bow shock that generates an entropy layer and strong streamwise flow acceleratation away from the stabgnation point. We apply input-output analysis based on numerical Jacobians to directly capture the effect of these physics upon instabilities leading to transition. The numerical Jacobian method extracts a global linear operator from the non-linear hypersonic flow solver US3D and does not make the assumptions of either the LST or PSE approaches, providing a more powerful tool for transition analysis. In this paper, the numerical Jacobian method along with input-output analysis is applied to 7o half-angle sharp and blunt cones at Mach 6. Our method is able to accurately predict growth and transition of both the second mode instability and the entropy layer instability for blunt cones of various radii, and provides new insight into the phenomenon of transition reversal.
|Original language||English (US)|
|Title of host publication||AIAA Aerospace Sciences Meeting|
|Publisher||American Institute of Aeronautics and Astronautics Inc, AIAA|
|State||Published - 2018|
|Event||AIAA Aerospace Sciences Meeting, 2018 - Kissimmee, United States|
Duration: Jan 8 2018 → Jan 12 2018
|Name||AIAA Aerospace Sciences Meeting, 2018|
|Other||AIAA Aerospace Sciences Meeting, 2018|
|Period||1/8/18 → 1/12/18|
Bibliographical noteFunding Information:
The authors gratefully acknowledge support from the Office of Naval Research under grants N00014-15-1-2522 and N00014-17-1-2496 and the Air Force Office of Scientific Research under grant FA9550-17-1-0250. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the ONR, the AFOSR or the U.S. Government.
© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.