scholarly journals Acoustic scattering from a fluid‐loaded elastic plate with a distributed inhomogeneity of varying length scales

1995 ◽  
Vol 98 (5) ◽  
pp. 2889-2889 ◽  
Author(s):  
Joe M. Cuschieri ◽  
David Feit
Keyword(s):  
Elastic Plate ◽  
Acoustic Scattering ◽  
Length Scales ◽  
Varying Length

Acoustic scattering by a finite nonlinear elastic plate. I Primary, secondary and combination resonances

1987 ◽  
Vol 414 (1846) ◽  
pp. 237-253 ◽  
Keyword(s):  
Incident Wave ◽  
Elastic Plate ◽  
Scattered Field ◽  
Acoustic Waves ◽  
Multiple Scales ◽  
Acoustic Scattering ◽  
Scattered Wave ◽  
Thin Elastic Plate ◽  
Finite Width ◽  
Wave Angle

A thin elastic plate of finite width is irradiated by time-harmonic acoustic waves. The fluid is assumed light compared with the plate mass, and the forcing term is of sufficient amplitude to necessitate the inclusion of a nonlinear term (due to mid-plane stretching) in the plate equation. The order-one scattered field is determined by the method of multiple scales when the forcing frequency approaches a free oscillation frequency (eigenfrequency) of the plate. This solution is shown to agree with previous work, for the linear problem, and can be multivalued for particular values of the plate-fluid parameters. The scattered wave may also exhibit jumps in its amplitude and phase angle as it varies with frequency, incident-wave angle or incident-wave amplitude. The non-linear term further allows the possibility of secondary and combination resonances. These are investigated and the scattered field is shown to contain terms of different frequencies to those of the incident waves. Multivalued solutions and the associated jump phenomenon are again found for these resonant cases.

Development of the Reattached Flow Behind Surface-Mounted Two-Dimensional Prisms

1988 ◽  
Vol 110 (2) ◽  
pp. 127-133 ◽  
Author(s):  
J. Antoniou ◽  
G. Bergeles
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Open Circuit ◽  
Two Dimensional ◽  
Blow Down ◽  
Length Scales ◽  
Turbulent Eddies ◽  
Flow Parameters ◽  
Varying Length ◽  
Dimensional Surface

Velocity and turbulence measurements are presented for the region after reattachment behind a two dimensional surface-mounted prism of varying length. The prism is mounted on the floor of an open circuit blow down wind tunnel and flow parameters for the developing boundary layer are deduced from the measurements; longitudinal integral time and length scales are estimated through autocorrelations. Reattchment on top of the prism, due to its increased length, affects the characteristics of the developing boundary layer; in this case the shear layer originating from the up-stream edge of the prism splits twice at reattachment points on top and behind the prism and the integral length scales of the turbulent eddies are found to be smaller due to the splitting.

Challenges in Modeling Ground Flares Using Computational Fluid Dynamics

2004 ◽  
Author(s):  
Philip Diwakar ◽  
Vibhor Mehrotra ◽  
Rimon Vallavanatt ◽  
Thomas McLean
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Large Scale ◽  
National Standard ◽  
Complex Nature ◽  
Large Area ◽  
Length Scales ◽  
Flow Problems ◽  
Varying Length ◽  
Wet Ground

Industrial application of Computational Fluid Dynamics (CFD) are varied and many. However CFD requires the solution of complex fluid-flow problems in conjunction with equipment design, process and product development and optimization. The solution of such complex problems is possible through the coordination between industrial CFD engineers, software developers, consultants and academic scientists. In the petrochemical industry, CFD may be used for a variety of purposes such as air recirculation studies in LNG plants, burners in coker furnaces, multiphase studies in heat exchangers to name just a few. In particular combustion, flames, flares and chemical reaction are of interest because of the physics and the complex nature of the process. The topic selected for this presentation is the study of wet ground flares during a large-scale propane release and the effect of the radiation release on the environment and surrounding buildings and vegetation. The flare characteristics and radiation on the surrounding terrain form an integral part of the information required by the National standard for “Control of Major Hazard Facilities”. The study of individual flames from each burner with nozzles of the order of 1mm and the effect of 180 burners in a large area and surrounding terrain with length scales of several hundred meters make up a very intriguing problem of varying length scales. The results of this analysis are presented concentrating on the effects during the large scale conflagration event on the surrounding buildings, vegetation, aircraft, hills and mangroves.

Acoustic scattering by a finite nonlinear elastic plate - II. Coupled primary and secondary resonances

1988 ◽  
Vol 418 (1854) ◽  
pp. 247-260 ◽  
Keyword(s):  
Elastic Plate ◽  
Acoustic Scattering ◽  
Sound Field ◽  
Thin Elastic Plate ◽  
Inviscid Fluid ◽  
Sound Waves ◽  
Secondary Resonances ◽  
Near Resonance ◽  
Plane Sound ◽  
Scattered Fields

A finite thin elastic plate is set in an infinite rigid baffle and the whole is immersed in a compressible inviscid fluid. Plane sound waves are incident on the elastic plate, and the fluid is assumed light compared with the plate density. Nonlinear terms in the plate equation have previously been found to markedly alter the scattered sound field near resonance; and it is shown in this paper that in-plane tension may result in simultaneous primary and secondary resonances. This coincidence of resonances gives rise to two scattered fields, one oscillating at the acoustic forcing frequency and the other at three times or one third of this frequency. Both terms have amplitudes which are of the same order as this incident wave and so under certain circumstances much of the incident energy is found to be scattered back off the plate at the secondary frequency.

Crack-front instability in a confined elastic film

2006 ◽  
Vol 462 (2075) ◽  
pp. 3233-3251 ◽  
Author(s):  
M Adda-Bedia ◽  
L Mahadevan
Keyword(s):  
Stability Analysis ◽  
Film Thickness ◽  
Elastic Plate ◽  
Linear Stability Analysis ◽  
Crack Front ◽  
Length Scales ◽  
Adhesive Film ◽  
Straight Crack ◽  
Multiple Length Scales ◽  
Elastic Film

We study the undulatory instability of a straight crack front generated by peeling a flexible elastic plate from a thin elastomeric adhesive film. We show that there is a threshold for the onset of the instability that is dependent on the ratio of two length-scales that arise naturally in the problem: the thickness of the film and an elastic length defined by the stiffness of the plate and that of the film. A linear stability analysis predicts that the wavelength of the instability scales linearly with the film thickness. Our results are qualitatively and quantitatively consistent with recent experiments, and show how crack fronts may lose stability due to a competition between bulk and surface effects in the presence of multiple length scales.

Acoustic scattering by a narrow crack in an elastic plate

Wave Motion ◽  
1996 ◽  
Vol 24 (1) ◽  
pp. 101-115 ◽  
Author(s):  
Ivan Andronov ◽  
Boris P. Belinskiy ◽  
Jerald P. Dauer
Keyword(s):  
Elastic Plate ◽  
Acoustic Scattering

Acoustic scattering by a finite elastic plate connecting two fluid-loaded parallel plates

1993 ◽  
Vol 443 (1918) ◽  
pp. 429-444 ◽  
Keyword(s):  
Elastic Plate ◽  
Acoustic Scattering ◽  
Elastic Plates ◽  
Parallel Plates ◽  
Fluid Loading ◽  
Heavy Fluid ◽  
Low Frequencies ◽  
Plane Sound ◽  
Two Fluid ◽  
Good Agreement

A plane sound wave is incident upon two infinite parallel elastic plates which are connected by a finite elastic plate. All three plates support compressional and bending motion, and interact with any compressible fluid with which they are in contact. A method, which can be applied to obtain numerical results, for calculating the sound scattered by the connecting plate is presented. In the absence of fluid between the plates an approximate solution, valid for low frequencies and heavy fluid-loading on the upper plate, has been derived which exhibits good agreement with results obtained numerically.

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