Wet Modes of Submerged Structures—Part 2: Applications

1992 ◽  
Vol 114 (4) ◽  
pp. 440-448 ◽  
Author(s):  
R. P. Daddazio ◽  
M. M. Ettouney ◽  
N. Abboud
Keyword(s):  
Pressure Wave ◽  
Elastic Shell ◽  
Computational Procedure ◽  
Surface Velocity ◽  
Acoustic Medium ◽  
Far Field ◽  
Harmonic Response ◽  
The Individual

Using the wet mode methodology described in Part I of this paper, we examine the harmonic response of an elastic shell in an infinite acoustic medium subjected to an incident pressure wave. Both surface and far field responses are studied utilizing this computational procedure. We investigate the sensitivity of response with respect to changes in frequency of oscillation of the system and geometry of the submerged structure. In addition, we compare the wet modes of the system and in vacuo modes of the structure. The propagation of the surface velocity wet modes to the far field is illustrated. The contribution of the individual modes to the far field pressure and surface velocities as a function of frequency and location is presented.

scholarly journals Structural and Acoustic Responses of a Submerged Stiffened Conical Shell

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Meixia Chen ◽  
Cong Zhang ◽  
Xiangfan Tao ◽  
Naiqi Deng
Keyword(s):  
Conical Shell ◽  
Element Model ◽  
Analytical Models ◽  
Superposition Method ◽  
Far Field ◽  
Fluid Loading ◽  
Low Frequencies ◽  
Structural Responses ◽  
The Individual ◽  
Field Sound

This paper studies the vibrational behavior and far-field sound radiation of a submerged stiffened conical shell at low frequencies. The solution for the dynamic response of the conical shell is presented in the form of a power series. A smeared approach is used to model the ring stiffeners. Fluid loading is taken into account by dividing the conical shell into narrow strips which are considered to be local cylindrical shells. The far-field sound pressure is solved by the Element Radiation Superposition Method. Excitations in two directions are considered to simulate the loading on the surface of the conical shell. These excitations are applied along the generator and normal to the surface of the conical shell. The contributions from the individual circumferential modes on the structural responses of the conical shell are studied. The effects of the external fluid loading and stiffeners are discussed. The results from the analytical models are validated by numerical results from a fully coupled finite element/boundary element model.

scholarly journals NON-STATIONARY PROBLEM OF THE PLANE OBLIQUE PRESSURE WAVE DIFFRACTION ON THIN SHELL IN THE SHAPE OF PARABOLIC CYLINDER

2019 ◽  
Vol 16 (32) ◽  
pp. 328-337
Author(s):  
Lev N. RABINSKIY
Keyword(s):  
Wave Diffraction ◽  
Pressure Wave ◽  
Differential Operators ◽  
Convex Surface ◽  
Elastic Shell ◽  
Auxiliary Problem ◽  
Stationary Problem ◽  
Transition Function ◽  
Parabolic Cylinder ◽  
The Impact

A non-stationary plane problem of the dynamics of thin elastic shell in the form of parabolic cylinder immersed in the fluid under the impact of the plane oblique pressure wave is considered. To solve this problem, a system of equations in the related formulation is constructed. Herewith, the hydroelasticity problems are reduced to the equations of the shell dynamics, the damping effect of fluid is taken into account by introducing an integral convolution type operator in the time domain which in the first approximation allows for accounting the capillary porosity of the shell material. The operator core is a surface transition function of the auxiliary problem of the plane acoustic pressure wave diffraction on a convex surface. The problem is solved approximately based on the thin layer hypothesis. The integral and differential equations of shell motion are solved numerically based on the difference discretization of differential operators and the representation of the integral operator by sum using the trapezium rule.

scholarly journals Vibrations attenuation of a system excited by unbalance and the ground movement by an impact element

2016 ◽  
Vol 1 (2) ◽  
pp. 603-616 ◽  
Author(s):  
Marek Lampart ◽  
Jaroslav Zapoměl
Keyword(s):  
Differential Equations ◽  
Research Work ◽  
Computational Procedure ◽  
Ground Movement ◽  
Frequency Interval ◽  
Nonlinear Behaviour ◽  
Helical Springs ◽  
Impact Element ◽  
The Individual ◽  
The Impact

AbstractThis paper concentrates on the vibrations attenuation of a rotor driven by a DC motor and its frame flexibly coupled with a baseplate by linear cylindrical helical springs and damped by an element that can work either in inertia or impact regime. The system oscillation is governed by three mutually coupled second-order ordinary differential equations. The nonlinear behaviour occurs if the impact regime is adjusted. The damping element operating in inertia mode reduces efficiently the oscillations amplitude only in a narrow frequency interval. In contrast, the damping device working in impact regime attenuates vibrations of the rotor frame in a wider range of the excitation frequencies and it can be easily extended if the clearances between the rotor casing and the damping element are controlled. The development of a computational procedure for investigation of vibration of a flexibly supported rotor and for its attenuation by the inertia and impact dampers; learning more on efficiency of the individual damping regimes; finding possibilities of extension of the frequency intervals of applicability of the damping device; and obtaining more information on the character of the vibration induced by impacts are the main contributions of this research work.

scholarly journals Corneal Buckling during Applanation and Its Effect on the Air Pressure Curve in Ocular Response Analyzer

2019 ◽  
Vol 16 (15) ◽  
pp. 2742 ◽  
Author(s):  
Agnieszka Jóźwik ◽  
Henryk Kasprzak ◽  
Agata Kozakiewicz
Keyword(s):  
Numerical Analysis ◽  
Pressure Wave ◽  
Biomechanical Properties ◽  
Air Pressure ◽  
Ocular Response Analyzer ◽  
Pressure Curve ◽  
Wave Disturbances ◽  
Local Wave ◽  
The Individual ◽  
First Time

The paper presents, for the first time, corneal buckling, during the air puff applanation, recorded with use of Ocular Response Analyzer (ORA), when the cornea is deeper deformed after its applanation. Precise numerical analysis of the air pressure curve from the raw data, distinct local disturbances of the curve, which appear almost exactly at the time of the first and the second applanations. Thirty measurements taken on six eyes show clear dependencies between times of both applanations and appearances of local wave disturbances on the air pressure curve as well as between the amplitude of pressure wave disturbances and the respective height of applanation curve. These findings can be interpreted as a result of very fast corneal buckling, that produces the air pressure wave, propagating from the cornea towards the device. The quantitative dependencies measured and described in this study, enable to characterize the individual buckling during respective applanations. Due to these individual characterizations and dependencies it is possible to understand and describe better the ultrafast corneal applanation process. Such phenomena could likely be employed to increase the accuracy of measured parameters by ORA or for identifying new types of biomechanical properties of the cornea.

RADIATED ACOUSTIC PRESSURE FROM A MOVING, NONUNIFORMLY VIBRATING CYLINDER WITH TWO SPHERICAL ENDCAPS

1994 ◽  
Vol 02 (01) ◽  
pp. 71-82 ◽  
Author(s):  
ZHAOXI WANG ◽  
SEAN F. WU
Keyword(s):  
Near Field ◽  
Translational Motion ◽  
Normal Component ◽  
Forward Direction ◽  
Numerical Results ◽  
Surface Velocity ◽  
Reverse Direction ◽  
Far Field ◽  
Field Source ◽  
Sound Diffraction

This paper presents numerical results of radiated acoustic pressures from a moving, nonuniformly vibrating cylinder with two spherical endcaps, based on an extended Kirchhoff integral formulation. Specifically, we consider cases in which the normal component of the surface velocity is nonzero on a portion of the surface, and zero elsewhere. Numerical results demonstrate that the radiation patterns depend critically on the frequency and source dimensions. For a noncompact source, the strongest radiation may not necessarily stem from a vibrating surface, but rather from a nonvibrating surface due to the effect of sound diffraction. The more noncompact the source is, the larger the number of side lobes in the near field and the more concentrated these side lobes will be. In the far field, however, the side lobes become smeared and less distinguishable. In other words, the effect of sound diffraction is greatly reduced in the far field. Source translational motion induces sound radiation in the perpendicular direction and enhances the radiated acoustic field in general. Enhancement in the forward direction is much greater than in the reverse direction.

Analysis of the State of Stress in the Hull of the Ship Kormoran II Loaded with Non-Contact Mine Explosion

2015 ◽  
Vol 236 ◽  
pp. 3-13 ◽  
Author(s):  
Bogdan Szturomski ◽  
Andrzej Grządziela ◽  
Radosław Kiciński
Keyword(s):  
Stress State ◽  
Pressure Distribution ◽  
Pressure Wave ◽  
The State ◽  
Acoustic Medium ◽  
Time Points ◽  
State Of Stress ◽  
The Way

In this paper an analysis of the stress state of the hull of the ship Kormoran II loaded by non-contact mine explosion were performed. An empirical description of the pressure wave from the non-contact TNT explosion loads reported by authors such as RH Cole T. L. Geers and K.S. Hunter was used. The way of modeling the pressure wave using the acoustic medium implemented CAE programs was shown. The paper presents the results of pressure distribution on the hull of the ship Kormoran II at selected time points from TNT explosion under the keel of the ship. The paper presents detailed results of the stress state in the selected nodes, for example on the frame of main motor construction.

Controlling the Tonal Characteristics of the Aerodynamic Noise Generated by Fan Rotors

1970 ◽  
Vol 92 (1) ◽  
pp. 143-154 ◽  
Author(s):  
R. C. Mellin ◽  
G. Sovran
Keyword(s):  
Background Noise ◽  
Pressure Wave ◽  
Sound Pressure ◽  
Axial Flow ◽  
Aerodynamic Noise ◽  
Wave Shape ◽  
Survey Technique ◽  
The Individual ◽  
Equal Spacing

A technique has been developed for selecting circumferentially-unequal blade spacings that will reduce the tonal annoyance of the aerodynamic noise generated by the rotors of fans. The procedure has been successfully applied to a number of axial-flow fans. The predictions of harmonic spectra are based on an experimentally-determined sound-pressure wave shape for the individual blades of such fans. However, the technique can be extended to other types of tonal-annoyance problems provided that the particular relevant sound-pressure wave shape is determined. Unequal blade spacings that will produce a particular degree of “whiteness” in the noise with a minimum departure from equal spacing are tabulated for a range of blade numbers. Both unbalanced and naturally balanced blading arrangements are considered. A survey technique is also outlined for those applications in which it is important to reduce a particular frequency, or where blending with a given background noise must be achieved.

Comparison of Three Types of Common Rail Systems Suited for Diesel Engines From 1 to 5 Megawatt

2006 ◽  
Author(s):  
Marco Ganser ◽  
Ulrich Moser
Keyword(s):  
Diesel Engines ◽  
Pressure Wave ◽  
Dynamic Pressure ◽  
Injection Pressure ◽  
Injection Rate ◽  
Common Rail ◽  
Wave Dynamics ◽  
Rail Systems ◽  
Heavy Duty Diesel ◽  
The Individual

The basic physical law governing the injection in Common Rail Systems is the compressibility of the fuel. The effects of pressure wave dynamics, the layout of the system volume and its geometrical distribution strongly affect the injection events at every injector. In this Paper, three different arrangements of system volumes and their effect upon the performance of the individual injectors are compared using the hydraulics simulation tool AMESim. Two systems are known in the passenger car and the heavy duty diesel engine domains. The third system is new and takes advantage of pressure wave dynamics to tailor the injection event. This system is best suited for Diesel Engines with a power from 1 to 5 MW, as used in locomotives, ships, power generation and heavy earthmoving machinery. It produces a more favorable pattern of the injection pressure and injection rate shape during any injection event by hydraulically interconnecting the individual injector’s accumulators during the injection and taking advantage of pressure wave dynamics. Right after the end of each injection, dynamic pressure pulsations are evened out with a dampening device. A multi-cylinder system provides equal conditions for all injections. Its very simple design and increased performance makes the novel system of very attractive use in the above mentioned fields.

scholarly journals Simulation of the impact resistance of Kilo type submarine loaded with non-contact mine explosion

2017 ◽  
pp. 99-110
Author(s):  
Bogdan Szturomski ◽  
Radosław Kiciński
Keyword(s):  
Finite Element Method ◽  
Pressure Wave ◽  
Impact Resistance ◽  
Acoustic Medium ◽  
The Finite Element Method ◽  
State Of Stress ◽  
Stress And Deformation ◽  
Submarine Hull ◽  
Explosion Load ◽  
The Impact

The paper presents simulations of the state of stress and deformation of the Kilo class submarine hull loaded from pressure wave of non-contact mine explosion. To accomplish the task the finite element method was used. Pressure wave was described by T. L. Geers’a and K. S. Hunter model. The way of modeling the pressure wave using the acoustic medium implemented to CAE programs was shown. To describe the material an elastic-plastic model of Jonson-Cook which takes into account the speed of deformation was used. The paper presents pressure distribution on the Kilo type submarine hull exposed on 100 kg of TNT explosion load in front of the bow of the ship.

A Technique to Predict the Acoustic Radiation Characteristics of an Automobile Tire

1986 ◽  
Vol 14 (2) ◽  
pp. 102-115 ◽  
Author(s):  
C. Wright ◽  
G. H. Koopmann
Keyword(s):  
Close Agreement ◽  
Sound Pressure ◽  
Acoustic Radiation ◽  
Surface Velocity ◽  
Experimental Measurements ◽  
Far Field ◽  
Radiation Characteristics ◽  
Automobile Tire ◽  
Electrodynamic Vibrator ◽  
Field Sound

Abstract A technique to predict the acoustic radiation characteristics of the predominant structural modes of an automobile tire is presented. A stationary tire is excited by an electrodynamic vibrator and, through conventional modal analysis methods, a description of the surface velocity is obtained. With this information, and a representation of the tire geometry, numerical procedures are used to predict the acoustic surface intensity and field pressure, for a given frequency of interest, based on a Helmholtz integral formulation. Predicted far field sound pressure levels are in close agreement with experimental measurements taken in an anechoic chamber. This provided the necessary validation of the technique.

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