scholarly journals Geometric-acoustics analysis of singly scattered, nonlinearly evolving waves by circular cylinders

2020 ◽  
Author(s):  
Michael Muhlestein ◽  
Carl Hart
Keyword(s):  
Acoustic Waves ◽  
Nonlinear Distortion ◽  
Nonlinear Evolution ◽  
Scattered Wave ◽  
High Amplitude ◽  
Circular Cylinders ◽  
Ray Theory ◽  
Theoretical Predictions ◽  
Geometric Acoustics ◽  
The Individual

Geometric acoustics, or acoustic ray theory, is used to analyze the scattering of high-amplitude acoustic waves incident upon rigid circular cylinders. Theoretical predictions of the nonlinear evolution of the scattered wave field are provided, as well as measures of the importance of accounting for nonlinearity. An analysis of scattering by many cylinders is also provided, though the effects of multiple scattering are not considered. Provided the characteristic nonlinear distortion length is much larger than a cylinder radius, the nonlinear evolution of the incident wave is shown to be of much greater importance to the overall evolution than the nonlinear evolution of the individual scattered waves.

scholarly journals Low-cost Solutions for Velocimetry in Rotating and Opaque Fluid Experiments using Ultrasonic Time of Flight

2021 ◽  
Author(s):  
Fabian Burmann ◽  
Jerome Noir ◽  
Stefan Beetschen ◽  
Andrew Jackson
Keyword(s):  
Acoustic Waves ◽  
Flow Measurement ◽  
Low Cost ◽  
Time Of Flight ◽  
Zonal Flow ◽  
Gravitational Acceleration ◽  
Complex Flow ◽  
Ultrasonic Time ◽  
Theoretical Predictions ◽  
Complex Flow Structure

AbstractMany common techniques for flow measurement, such as Particle Image Velocimetry (PIV) or Ultrasonic Doppler Velocimetry (UDV), rely on the presence of reflectors in the fluid. These methods fail to operate when e.g centrifugal or gravitational acceleration leads to a rarefaction of scatterers in the fluid, as for instance in rapidly rotating experiments. In this article we present two low-cost implementations for flow measurement based on the transit time (or Time of Flight) of acoustic waves, that do not require the presence of scatterers in the fluid. We compare our two implementations against UDV in a well controlled experiment with a simple oscillating flow and show we can achieve measurements in the sub-centimeter per second velocity range with an accuracy of $\sim 5-10\%$ ∼ 5 − 10 % . We also perform measurements in a rotating experiment with a complex flow structure from which we extract the mean zonal flow, which is in good agreement with theoretical predictions.

scholarly journals Indirectness in the Age of Globalization: A Social Network Analysis

2019 ◽  
Vol 23 (4) ◽  
pp. 930-949
Author(s):  
Marina Terkourafi
Keyword(s):  
African American ◽  
American English ◽  
Historical Context ◽  
Theory Building ◽  
Network Ties ◽  
British English ◽  
Theoretical Predictions ◽  
The Individual ◽  
Individual Self

Indirectness has traditionally been viewed as commensurate with politeness and attributed to the speaker’s wish to avoid imposition and/or otherwise strategically manipulate the addressee. Despite these theoretical predictions, a number of studies have documented the solidarity-building and identity-constituting functions of indirectness. Bringing these studies together, Terkourafi 2014 proposed an expanded view of the functions of indirect speech, which crucially emphasizes the role of the addressee and the importance of network ties. This article focuses on what happens when such network ties become loosened, as a result of processes of urbanization and globalization. Drawing on examples from African American English and Chinese, it is argued that these processes produce a need for increased explicitness, which drives speakers (and listeners) away from indirectness. This claim is further supported diachronically, by changes in British English politeness that coincide with the rise of the individual Self. These empirical findings have implications for im/politeness theorizing and theory-building more generally, calling attention to how the socio-historical context of our research necessarily influences the theories we end up building.

W-shape bright and several other solutions to the (3+1)-dimensional nonlinear evolution equations

2021 ◽  
pp. 2150468
Author(s):  
Youssoufa Saliou ◽  
Souleymanou Abbagari ◽  
Alphonse Houwe ◽  
M. S. Osman ◽  
Doka Serge Yamigno ◽  
...  
Keyword(s):  
Acoustic Waves ◽  
Evolution Equations ◽  
Nonlinear Evolution ◽  
Nonlinear Evolution Equations ◽  
Singular Function ◽  
Ion Acoustic Waves ◽  
Weakly Nonlinear ◽  
Quantum Electron ◽  
Ion Acoustic ◽  
Trigonometric Function Solutions

By employing the Modified Sardar Sub-Equation Method (MSEM), several solitons such as W-shape bright, dark solitons, trigonometric function solutions and singular function solutions have been obtained in two famous nonlinear evolution equations which are used to describe waves in quantum electron–positron–ion magnetoplasmas and weakly nonlinear ion-acoustic waves in a plasma. These models are the (3+1)-dimensional nonlinear extended quantum Zakharov–Kuznetsov (NLEQZK) equation and the (3+1)-dimensional nonlinear modified Zakharov–Kuznetsov (NLmZK) equation, respectively. Comparing the obtained results with Refs. 32–34 and Refs. 43–46, additional soliton-like solutions have been retrieved and will be useful in future to explain the interaction between lower nonlinear ion-acoustic waves and the parameters of the MSEM and the obtained figures will have more physical explanation.

scholarly journals Gradient index phononic crystals and metamaterials

Nanophotonics ◽  
2019 ◽  
Vol 8 (5) ◽  
pp. 685-701 ◽  
Author(s):  
Yabin Jin ◽  
Bahram Djafari-Rouhani ◽  
Daniel Torrent
Keyword(s):  
Refractive Index ◽  
Wave Propagation ◽  
Acoustic Waves ◽  
Effective Properties ◽  
Periodic Structures ◽  
Phononic Crystals ◽  
Ray Theory ◽  
Acoustic Metamaterials ◽  
Propagation Of Waves ◽  
At Will

AbstractPhononic crystals and acoustic metamaterials are periodic structures whose effective properties can be tailored at will to achieve extreme control on wave propagation. Their refractive index is obtained from the homogenization of the infinite periodic system, but it is possible to locally change the properties of a finite crystal in such a way that it results in an effective gradient of the refractive index. In such case the propagation of waves can be accurately described by means of ray theory, and different refractive devices can be designed in the framework of wave propagation in inhomogeneous media. In this paper we review the different devices that have been studied for the control of both bulk and guided acoustic waves based on graded phononic crystals.

scholarly journals The acoustic waves propagation in a cylindrical waveguide with the laminar flow

2018 ◽  
Vol 211 ◽  
pp. 04005
Author(s):  
Alexander Petrov ◽  
Valentina Rumyantseva
Keyword(s):  
Wave Propagation ◽  
Laminar Flow ◽  
Acoustic Waves ◽  
Approximate Analytical Solution ◽  
Acoustic Oscillations ◽  
Acoustic Wave Propagation ◽  
Inhomogeneous Flow ◽  
Waves Propagation ◽  
The Individual ◽  
Hydrodynamics Equations

The problem of modeling of acoustic wave propagation in inhomogeneous flow is considered. There is an approximate analytical solution of the hydrodynamics equations in the presence of annular acoustic oscillations source in the case of laminar flow. Special attention is to paid to the propagation of acoustic waves modes. The amplitudes and phases dependences of the individual modes on the Mach number in the linear approximation were established.

scholarly journals Flow in the exit of open pipes during acoustic resonance

1980 ◽  
Vol 99 (2) ◽  
pp. 293-319 ◽  
Author(s):  
J. H. M. Disselhorst ◽  
L. Van Wijngaarden
Keyword(s):  
Boundary Layer ◽  
Mathematical Model ◽  
Boundary Condition ◽  
Acoustic Wave ◽  
Acoustic Waves ◽  
Acoustic Radiation ◽  
Acoustic Resonance ◽  
The Other ◽  
Open Tube ◽  
Theoretical Predictions

The flow near the mouth of an open tube is examined, experimentally and theoretically, under conditions in which resonant acoustic waves are excited in the tube at the other end. If the edge of the tube is round, separation does not occur at high Strouhal numbers, which enables us to verify theoretical predictions for dissipation in the boundary layer and for acoustic radiation. Observation with the aid of schlieren pictures shows that in the case of a sharp edge vortices are formed during inflow. The vortices are shed from the pipe during outflow. Based on these observations a mathematical model is developed for the generation and shedding of vorticity. The main result of the analysis is a boundary condition for the pressure in the wave, to be applied near the mouth. The pressure amplitudes in the acoustic wave measured under resonance are compared with theoretical predictions made with the aid of the boundary condition obtained in the paper.

Laser generation of high amplitude surface acoustic waves

1990 ◽  
Author(s):  
V. Dymshakov ◽  
A. Dychne ◽  
Fedor V. Lebedev ◽  
Vladislav D. Pis'mennyi
Keyword(s):  
Acoustic Waves ◽  
Surface Acoustic Waves ◽  
High Amplitude ◽  
Laser Generation
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