Nose Bluntness Effects on the Amplification of External Disturbances in Hypersonic Flows

Luke Melander, Anubhav Dwivedi, Graham V. Candler

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Experiments and computations have extensively studied hypersonic boundary layer transition over sharp and blunt cones. Transition on sharp and small bluntness cones is dominated by modal growth of planar waves. As bluntness increases, an entropy layer develops that stabilizes Mack modes and pushes the transition front downstream. Experiments show that beyond a critical nose bluntness, downstream movement of the transition front reverses and despite being modally stable the transition front moves up to the nose tip. Despite many experimental and numerical investigations, the transition reversal phenomenon has not been clearly linked to a physical mechanism. In this study, direct numerical simulation (DNS) and input-output (IO) are utilized to study the effects of nose bluntness on the amplification of external disturbances. DNS is performed on low dissipation baseflows that are forced stochastically with freestream noise and wall roughness. Spectral proper orthogonal decomposition is used on snapshots of the statistically steady state DNS solution to isolate globally dominant resolvent modes. An input-output framework is used to study the optimal flow response to forcing in the linear regime. Results from both the DNS and IO identify low frequency streak-like structures that grow significantly on the nose tip.These structures are shown to exist on both intermediate bluntness (1.524 mm radius) cones and large bluntness (15.24 mm radius) cones, but grow 2 orders of magnitude more in the large bluntness case. The structures are extremely receptive to roughness. The low frequency streak-like structures identified in this work behave in accordance with experimental observations of transition reversal, potentially providing a physical mechanism to explain the phenomenon.

Original languageEnglish (US)
Title of host publicationAIAA SciTech Forum 2022
PublisherAmerican Institute of Aeronautics and Astronautics Inc, AIAA
ISBN (Print)9781624106316
DOIs
StatePublished - 2022
EventAIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2022 - San Diego, United States
Duration: Jan 3 2022Jan 7 2022

Publication series

NameAIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2022

Conference

ConferenceAIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2022
Country/TerritoryUnited States
CitySan Diego
Period1/3/221/7/22

Bibliographical note

Funding Information:
This work was sponsored by the Air Force Office of Scientific Research (AFOSR) under grants FA9550-18-1-0009 and the Office of Naval Research (ONR) under grant N000141912037. 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 AFOSR, ONR, or the U.S. Government.

Publisher Copyright:
© 2022, American Institute of Aeronautics and Astronautics Inc.. All rights reserved.

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