Sound generation in the vicinity of the sea surface: Source mechanisms and the coupling to the received sound field

1991 ◽  
Vol 89 (3) ◽  
pp. 1076-1095 ◽  
Author(s):  
Douglas H. Cato
Keyword(s):  
Sound Field ◽  
Sea Surface ◽  
Sound Generation ◽  
Surface Source ◽  
Source Mechanisms

scholarly journals Modeling transient vibration-sound generation processes

2020 ◽  
pp. 39-42
Author(s):  
Petro Volodymyrovich Lukianov
Keyword(s):  
Comparative Analysis ◽  
Mach Number ◽  
Sound Field ◽  
Numerical Results ◽  
Sound Generation ◽  
Transient Vibration ◽  
Helicopter Landing ◽  
Blade Flutter ◽  
Sinusoidal Shape ◽  
Transitional Mode

In this paper, a problem of sound generation of two-blade rotor sinusoidal shape during helicopter landing is solved. Near and far sound field characteristics have been calculated. A comparative analysis of obtained numerical results with results for Mach number 0.2<M<0.4 is given. In particular noticed, that for a low Mach’s number M<0.1 transitional mode can occurs, which produces a blade flutter as a result.

Sound generation by a supersonic aerofoil cutting through a steady jet flow

1990 ◽  
Vol 216 ◽  
pp. 193-212 ◽  
Author(s):  
Y. P. Guo
Keyword(s):  
Vortex Shedding ◽  
Sound Field ◽  
Leading Edge ◽  
Jet Flow ◽  
Generation Process ◽  
Sound Waves ◽  
Leading Order ◽  
Sound Generation ◽  
Trailing Edge ◽  
Kutta Condition

This paper examines the sound generation process when a supersonic aerofoil cuts through a steady jet flow. It is shown that the principal sound is generated by the leading edge of the aerofoil when it interacts with the streaming jet. To the leading order in terms of the jet velocity, no trailing-edge sound is generated. This is not the result of the cancellation of a trailing-edge sound by that from vortex shedding through the imposition of the Kutta condition. Instead, the null acoustic radiation from the trailing edge is entirely because, to the leading order, there is no interaction between the trailing edge and the jet. The effect of the trailing edge is to diffract sound waves generated by the leading edge. It is shown that the diffracted field (as well as the incident field) is regular at the trailing edge and the issue of satisfying the Kutta condition does not arise during the diffraction process. Thus, there is no extra vortex shedding from the trailing edge owing to its interaction with the flow, apart from those resulting from the discontinuity across the aerofoil, generated by the flow-leading edge interaction. This is in sharp contrast to the case of subsonic aerofoils where the removal of the singularity in the diffracted field at the trailing edge through the imposition of the Kutta condition results in vortex shedding from the sharp edge and energy exchange between the sound field and the vortical wake.

Analysis of the Influence of Sea-Surface Reflection on Locating the Underwater Sound Source

2015 ◽  
Vol 727-728 ◽  
pp. 813-818
Author(s):  
Qi Wei He ◽  
Guo Liang Xu ◽  
Shao Chun Ding ◽  
Zhen Dai
Keyword(s):  
Half Space ◽  
Sound Source ◽  
Near Field ◽  
Sound Field ◽  
Sea Surface ◽  
Underwater Sound ◽  
Underwater Acoustic ◽  
Surface Reflection ◽  
Conventional Technology ◽  
The Impact

When test the underwater acoustic in the half-space which the sea-surface separate the free-space to,the conventional technology of PNAH can't be used to locate the underwater sound source.In order to solve the impact of the sea-surface reflection on the underwater acoustic testing,in this paper,use the method of mirror imaging to correct the sound field in the half-space.In this paper,introduce the principles and procedures of the method of mirror imaging to correct the sound field in the half-space.Simulate that make a sound field transformation of the corrected sound field in the half-space by the technology of planar near field acoustic holography in order to reconstruct the sound field of sound source surface.The simulation results show the influence of the sea-surface reflection on locating,and verify the effectiveness that use the method of mirror imaging to solve sea-surface reflection.Works above provide a reference for locating the underwater sound source.

Sea surface source-side static optimization for 4D seismic

2017 ◽  
Author(s):  
Simon Barnes ◽  
Paul Lecocq ◽  
Stephane Perrier ◽  
Mick Igoe
Keyword(s):  
Sea Surface ◽  
Surface Source ◽  
Static Optimization ◽  
4D Seismic

Numerical Analysis of Sound Generation by a Two-Dimensional Cylinder in a Uniform Flow

2003 ◽  
Author(s):  
Ayaka Imamura ◽  
Nozomu Hatakeyama ◽  
Osamu Inoue
Keyword(s):  
Sound Pressure ◽  
Stokes Equations ◽  
Sound Field ◽  
Uniform Flow ◽  
Navier Stokes ◽  
Pressure Waves ◽  
Two Dimensional ◽  
Sound Generation ◽  
Navier Stokes Equations ◽  
Characteristic Features

The sound generated by a squarer cylinder in a uniform flow is investigated by direct numerical simulation of the two-dimensional compressible Navier–Stokes equations. The characteristic features of the generated sound are investigated and compared for different configurations and angles of attack. Results show that sound pressure waves are generated by vortex shedding from the cylinder into its wake. The sound field is dominated by lift dipole. The effect of the angle of attack on the sound generation and propagation is also analyzed.

Influence of incidence angle on sound generation by airfoils interacting with high-frequency gusts

1995 ◽  
Vol 292 ◽  
pp. 271-304 ◽  
Author(s):  
Matthew R. Myers ◽  
E. J. Kerschen
Keyword(s):  
High Frequency ◽  
Incidence Angle ◽  
Outer Region ◽  
Sound Field ◽  
Leading Edge ◽  
Edge Region ◽  
Sound Generation ◽  
Mean Flow ◽  
Flow Stagnation ◽  
Trailing Edges

A theoretical model is developed for the sound generated when a convected vortical or entropic gust encounters an airfoil at non-zero angle of attack. The theory is based on a linearization of the Euler equations about the steady subsonic flow past the airfoil. High-frequency gusts, whose wavelengths are short compared to the airfoil chord, but long compared to the displacement of the mean-flow stagnation point from the leading edge, are considered. The analysis utilizes singular-perturbation techniques and involves four asymptotic regions. Local regions, which scale on the gust wavelength, are present at the airfoil leading and trailing edges. Behind the airfoil a ‘transition’ region, which is similar to the transition zone between illuminated and shadow zones in optical problems, is present. In the outer region, far away from the airfoil edges and wake, the solution has a geometric-acoustics form. The primary sound generation is found to be concentrated in the local leading-edge region. The trailing edge plays a secondary role as a scatterer of the sound generated in the leading-edge region. Parametric calculations are presented which illustrate that moderate levels of airfoil steady loading can significantly affect the sound field produced by airfoil–gust interactions.

scholarly journals The Effects of Bubble Scattering on Sound Propagation in Shallow Water

2021 ◽  
Vol 9 (12) ◽  
pp. 1441
Author(s):  
Ruoyun Liu ◽  
Zhenglin Li
Keyword(s):  
Energy Loss ◽  
Shallow Water ◽  
Sound Propagation ◽  
Transmission Loss ◽  
Sound Field ◽  
Sea Surface ◽  
Statistical Characteristics ◽  
Strong Wind ◽  
Scattering Attenuation ◽  
Bubble Layer

As sea waves break, a bubble layer forms beneath the sea surface. The bubble scattering affects sound propagation, thus influencing the accuracy of sound field prediction. This paper aims to investigate the effects of bubble scattering on the statistical characteristics of the sound field, the distribution of transmission loss (TL), and the average scattering attenuation in shallow water. A bubble layer model based on the bubble spectrum and a parallel Parabolic Equation (PE) model are combined to calculate and analyse the sound field in the marine environment with bubbles. The effects of the bubble layer are then compared with those of the fluctuant sea surface. The results show that the bubble scattering causes additional energy loss and random fluctuations of the sound field. The TL distribution properties and the average scattering attenuation are related to the wind speed, range, frequency, and source position relative to the negative gradient sound speed layer in shallow water. The comparison demonstrates that the random variation caused by the fluctuation of the sea surface is more significant than that caused by bubbles, and the energy loss caused by bubble scattering is more significant than the fluctuant sea surface under strong wind conditions.

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