Stabilization Of Hypersonic Boundary Layer Acoustic Metasurfaces
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Stabilization Of Hypersonic Boundary Layer Acoustic Metasurfaces
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Author : Rui Zhao
language : en
Publisher: Springer Nature
Release Date : 2025-05-05
Stabilization Of Hypersonic Boundary Layer Acoustic Metasurfaces written by Rui Zhao and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2025-05-05 with Technology & Engineering categories.
This book explores the mechanisms and applications of acoustic metasurfaces in the hypersonic transition control area. It begins with an introduction of the concepts of acoustic metasurface and hypersonic boundary-layer stabilization, which also provides a full scene of the research progress in the past two decades. This book then discusses the modeling methods of various acoustic metasurfaces, including the regular and irregular ones, and describes how the models are to be used in theoretical analysis and numerical calculations. The design strategies and optimization methods are presented to promote the applications in the engineering community. The possible stabilization mechanisms are explored, and the proposed analysis methods are used to clarify other flow instabilities. This book delivers valuable insight for aerospace engineers, postgraduate students, and researchers.
Receptivity Of Hypersonic Boundary Layers To Distributed Roughness And Acoustic Disturbances
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Author : National Aeronautics and Space Adm Nasa
language : en
Publisher: Independently Published
Release Date : 2019-01-18
Receptivity Of Hypersonic Boundary Layers To Distributed Roughness And Acoustic Disturbances written by National Aeronautics and Space Adm Nasa and has been published by Independently Published this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019-01-18 with Science categories.
Boundary-layer receptivity and stability of Mach 6 flow over smooth and rough 7 half-angle sharp-tipped cones are numerically investigated. The receptivity of the boundary layer to slow acoustic disturbances, fast acoustic disturbances, and vortical disturbances are considered. The effects of two-dimensional isolated and distributed roughness on the receptivity and stability are also simulated. The results show that the instability waves are generated in the leading edge region and that the boundary layer is much more receptive to slow acoustic waves than to the fast waves. Vortical disturbances also generate unstable second modes, however the receptivity coefficients are smaller than that of the slow acoustic wave. An isolated two-dimensional roughness element of height h/delta =1/4 did not produce any difference in the receptivity or in the stability of the boundary layer. Distributed roughness elements produced a small decrease in the receptivity coefficient and also stabilized the boundary layer by small amounts. Balakumar, Ponnampalam Langley Research Center NF1676L-14447
Stabilization Of Hypersonic Boundary Layers By Porous Coatings
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Author : Alexander V. Fedorov
language : en
Publisher:
Release Date : 2001
Stabilization Of Hypersonic Boundary Layers By Porous Coatings written by Alexander V. Fedorov and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2001 with categories.
Supersonic Unstable Modes In Hypersonic Boundary Layers With Thermochemical Nonequilibrium Effects
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Author : Carleton Knisely
language : en
Publisher:
Release Date : 2018
Supersonic Unstable Modes In Hypersonic Boundary Layers With Thermochemical Nonequilibrium Effects written by Carleton Knisely and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.
Mack's second mode has been known to be the dominant disturbance leading to transition to turbulence in traditional hypersonic boundary layer flows at zero angle of attack. Physically, the second mode exists due to trapped acoustic waves within the boundary layer. The second mode has been widely studied and the conditions that stabilize or amplify the second mode are well documented. Predicting the second mode amplification is the basis of contemporary transition prediction techniques such as the eN method. There has been a renewed interest in studying hypersonic boundary layer stability in high-enthalpy flows with highly-cooled walls due to its applicability to experiments and some real flight conditions. One physical phenomenon that occurs in these flows is the creation of a supersonic mode, which is associated with an unstable mode F1 synchronizing with the slow acoustic spectrum. This causes the disturbance to travel upstream supersonically relative to the mean flow outside the boundary layer and radiate sound away from the boundary layer. The supersonic mode has been known to exist for decades, but has until recently been deemed negligible in comparison to the second mode. However, a resurgence in interest in the supersonic mode has shown the supersonic mode to exist in unexpected conditions with considerable peak growth rates compared to the second mode. Namely, recent research in the field has shown the supersonic mode in hot-wall flows, upending the notion that it is an artifact of highly-cooled walls. Additionally, a dominant supersonic mode with significantly larger growth rate than the second mode has been found on very blunt cones. Therefore, because the supersonic mode has not been systematically investigated, the mechanism of its creation and the conditions under which it exists are not yet clear. The objective of this work is to systematically investigate the supersonic mode using numerical and theoretical tools to simulate hypersonic flow over blunt cones. Specifically, this work aims to (1) Determine the characteristics of the supersonic mode and under what conditions it exists, (2) Explore the effectiveness of Linear Stability Theory (LST) on predicting the supersonic mode, and (3) Examine the impact of the supersonic mode on transition to turbulence under realistic flight or experimental conditions. This work explores the supersonic mode on a 1 mm nose radius cone in various free stream flow configurations with a 5-species, two-temperature nonequilibrium gas model for air. A combined approach of Direct Numerical Simulation (DNS) and Linear Stability Theory (LST) are used to numerically investigate the supersonic mode. New LST equations with linearized Rankine-Hugoniot shock relation boundary conditions are derived and verified. In addition, a theoretical schematic has been developed to aid future experimentalists and those performing DNS in visualizing the supersonic mode. Mach numbers of 5 and 10 are considered with wall-temperature-to-free-stream-temperature ratios (Tw/T ) between 0.2 and 1.43. Additionally, the impact of thermochemical nonequilibrium on the supersonic mode is assessed. Both LST and DNS results have confirmed the existence of the supersonic mode on a Mach 5 axisymmetric cold-wall (Tw/T = 0.2) cone. On a warmer wall (Tw/T = 0.667) under the same free stream conditions, LST indicated the supersonic mode was stabilized, although some weak sound radiation was still apparent in DNS. For the Mach 10 case, LST predicted a stable supersonic mode for both wall temperature cases (Tw/T = 1.43, Tw/T = 0.43), however a prominent supersonic mode was observed in DNS. The supersonic mode was determined to be excited via a modal interaction that is ignored in LST due to the independent mode assumption. Furthermore, the supersonic mode in the Mach 10 case with Tw/T = 0.43 exhibited a stronger peak growth rate for the supersonic mode compared to Mack's traditional second mode. These findings illustrate the need for combined LST and DNS studies of the supersonic mode. Overall, this study has determined that the supersonic mode is destabilized by largely the same factors as Mack's second mode. Namely, wall cooling is destabilizing, increasing Mach number/stagnation enthalpy is destabilizing, and vibrational nonequilibrium is stabilizing. The impact of chemical nonequilibrium is hypothesized to be slightly destabilizing, although was not able to be confirmed with the cases explored here. Based on the results presented here, transition prediction analyses relying on LST, such as the eN method, should be used with caution when applied to the supersonic mode, as it has been shown that LST may not fully capture the mechanism of the supersonic mode's creation.
Hypersonic Boundary Layer Receptivity To Acoustic Disturbances Over Cones
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Author : Kursat Kara
language : en
Publisher:
Release Date : 2008
Hypersonic Boundary Layer Receptivity To Acoustic Disturbances Over Cones written by Kursat Kara and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with Acoustical engineering categories.
Receptivity Of Hypersonic Boundary Layer To Acoustic Disturbances Scattered By Surface Roughness
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Author : A. V. Fedorov
language : en
Publisher:
Release Date : 2003
Receptivity Of Hypersonic Boundary Layer To Acoustic Disturbances Scattered By Surface Roughness written by A. V. Fedorov and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003 with categories.
Receptivity Of Hypersonic Boundary Layer To Acoustic Disturbances Scattered By Surface Roughness
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Author :
language : en
Publisher:
Release Date : 1999
Receptivity Of Hypersonic Boundary Layer To Acoustic Disturbances Scattered By Surface Roughness written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1999 with categories.
This report results from a contract tasking Moscow Institute of Physics and Technology as follows: The contractor will perform theoretical analysis on the receptivity of hypersonic boundary layer to acoustic disturbances as outlined in his proposal submitted in May 98.
Comments On Hypersonic Boundary Layer Transition
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Author : Kenneth F. Stetson
language : en
Publisher:
Release Date : 1990
Comments On Hypersonic Boundary Layer Transition written by Kenneth F. Stetson and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1990 with Aerodynamics, Hypersonic categories.
This is a survey paper on the subject of hypersonic boundary-layer transition. Part 1 discusses boundary-layer stability theory, hypersonic boundary-layer stability experiments, and a comparison between theory and experiment. Part 2 contains comments on how many configuration and flow parameters influence transition. Part 3 discusses some additional general aspects of transition. Part 4 discusses problems of predicting transition and comments on three prediction methods. Part 5 contains some general guidelines for prediction methodology. Keywords: Boundary layer transition, Boundary layer stability, Hypersonic boundary layers.
Spatial Evolution Of Nonlinear Acoustic Mode Instabilities On Hypersonic Boundary Layers
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Author :
language : en
Publisher:
Release Date : 1989
Spatial Evolution Of Nonlinear Acoustic Mode Instabilities On Hypersonic Boundary Layers written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1989 with categories.
Direct Numerical Simulation And Experimental Validation Of Hypersonic Boundary Layer Receptivity And Instability
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Author : Xiaolin Zhong
language : en
Publisher:
Release Date : 2007
Direct Numerical Simulation And Experimental Validation Of Hypersonic Boundary Layer Receptivity And Instability written by Xiaolin Zhong and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with Aerodynamics, Hypersonic categories.
The objective of this research project is to compare our numerical simulation solutions with available experimental or theoretical results on hypersonic boundary layer receptivity and stability; and to conduct extensive DNS studies on the flow mechanisms of hypersonic boundary layer receptivity and stability. During the three-year period, we have conducted extensive DNS studies on the receptivity of hypersonic boundary layer flows over a sharp wedge, a flat plate, a blunt cone, and the FRESH aeroshell. DNS studies are compared with Stetson's 1984 stability experiment on Mach 7.99 flow over a blunt cone, and Maslov's leading-edge receptivity experiment on Mach 5.92 flow over a flat plate. Our numerical studies have been validated to be of high accuracy and led to further understanding of hypersonic boundary layer receptivity mechanism. Such understanding can lead to better tools for the prediction and control of high-speed boundary layer transition.