Generation of first Mack modes in supersonic boundary layers by slow acoustic waves interacting with streamwise isolated wall roughness

2020 ◽  
Vol 888 ◽  
Author(s):  
Yinhui Liu ◽  
Ming Dong ◽  
Xuesong Wu
Keyword(s):  
Boundary Layers ◽  
Acoustic Waves ◽  
Wall Roughness ◽  
Image Position

scholarly journals On the role of acoustic feedback in boundary-layer instability

2014 ◽  
Vol 372 (2020) ◽  
pp. 20130347 ◽  
Author(s):  
Xuesong Wu
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Acoustic Waves ◽  
Feedback Loop ◽  
Peak Frequency ◽  
S Wave ◽  
Flat Plates ◽  
Acoustic Coupling ◽  
Acoustic Feedback ◽  
Roughness Elements

In this paper, the classical triple-deck formalism is employed to investigate two instability problems in which an acoustic feedback loop plays an essential role. The first concerns a subsonic boundary layer over a flat plate on which two well-separated roughness elements are present. A spatially amplifying Tollmien–Schlichting (T–S) wave between the roughness elements is scattered by the downstream roughness to emit a sound wave that propagates upstream and impinges on the upstream roughness to regenerate the T–S wave, thereby forming a closed feedback loop in the streamwise direction. Numerical calculations suggest that, at high Reynolds numbers and for moderate roughness heights, the long-range acoustic coupling may lead to absolute instability, which is characterized by self-sustained oscillations at discrete frequencies. The dominant peak frequency may jump from one value to another as the Reynolds number, or the distance between the roughness elements, is varied gradually. The second problem concerns the supersonic ‘twin boundary layers’ that develop along two well-separated parallel flat plates. The two boundary layers are in mutual interaction through the impinging and reflected acoustic waves. It is found that the interaction leads to a new instability that is absent in the unconfined boundary layer.

RECEPTIVITY OF ACOUSTIC WAVES ON LOCALIZED ROUGHNESS IN COMPRESSIBLE LAMINAR BOUNDARY LAYERS

2021 ◽  
Author(s):  
Pedro Henrique Rosa dos Santos ◽  
Fernando Henrique Tadashi Himeno ◽  
Marlon Sproesser Mathias ◽  
Marcello Augusto Faraco de Medeiros
Keyword(s):  
Boundary Layers ◽  
Acoustic Waves ◽  
Laminar Boundary Layers

Effects of Disturbed Nozzle-exit Boundary Layers on Acoustic Waves from Ideally-expanded Supersonic Jet

2016 ◽  
Author(s):  
Taku Nonomura ◽  
Akira Oyama ◽  
Kozo Fujii ◽  
Koichi Morihira ◽  
Gabriel Pichon ◽  
...  
Keyword(s):  
Boundary Layers ◽  
Nozzle Exit ◽  
Acoustic Waves ◽  
Supersonic Jet ◽  
Exit Boundary

Measuring the volume charge in dielectric films using single frequency electro-acoustic waves

2014 ◽  
Vol 29 (4) ◽  
pp. 501-508 ◽  
Author(s):  
Dongfei Pei ◽  
Yuri M. Shkel ◽  
Daniel J. Klingenberg ◽  
Zakai I. Segal ◽  
Yoshio Nishi ◽  
...  
Keyword(s):  
Acoustic Waves ◽  
Single Frequency ◽  
Dielectric Films ◽  
Volume Charge ◽  
Image Position

Abstract

scholarly journals On the role of actuation for the control of streaky structures in boundary layers

2019 ◽  
Vol 883 ◽  
Author(s):  
Kenzo Sasaki ◽  
Pierluigi Morra ◽  
André V. G. Cavalieri ◽  
Ardeshir Hanifi ◽  
Dan S. Henningson
Keyword(s):  
Boundary Layers ◽  
Streaky Structures ◽  
Image Position

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