Sound Radiation From a Propeller in a Submerged Rib-Stiffened Duct

2008 ◽  
Author(s):  
Wenlong Zhang ◽  
Hafiz M. Atassi
Keyword(s):  
Dispersion Relation ◽  
Acoustic Radiation ◽  
Strength Distribution ◽  
Acoustic Response ◽  
Dipole Strength ◽  
Compact Source ◽  
Source Effects ◽  
Internal Forces ◽  
Radiated Sound ◽  
Propeller Blades

This paper examines the interaction of nonuniform flows with propeller blades in a submerged elastic duct. The acoustic radiation from the duct is calculated and correlated to the flow nonuniformities and the propeller and duct characteristics. The case of a stiffened duct with ribs is also considered and the dispersion relation of the duct modes is compared with that of a regular duct. The dispersion relation of the stiffened duct has a periodic structure similar to that of connected oscillators with large number of independent modes. Because of our interest in the acoustic radiation of such a system, we focus our attention on the flexure modes. The model is first tested with simple internal forces such as monopoles and dipoles. The results for unstiffened ducts show strong directivity as the dipole radial location moves closer to the duct wall. For stiffened ducts, the magnitude of the acoustic response as well as the directivity vary strongly and show large peaks near the stiffened duct free modes. For a propeller, an Euler code provides the pressure distribution along the blades. This represents the dipole strength distribution. Its radiated sound is calculated by summing up the contribution of the distributed dipoles. In this process, compact source effects are also taken into account.

Quieting Plate Modes With Optimally Sized Point Masses: A Volume Velocity Approach

1995 ◽  
Author(s):  
Hans-Walter Wodtke ◽  
Gary H. Koopmann
Keyword(s):  
Acoustic Radiation ◽  
Sound Intensity ◽  
Structural Vibration ◽  
Acoustic Response ◽  
Radiation Problem ◽  
Volume Velocity ◽  
Intensity Measurements ◽  
Radiated Sound ◽  
The Masses ◽  
Radiated Sound Power

Abstract The radiated sound power of the second symmetric mode of a clamped square plate is minimized by attaching optimally sized point masses to the plate. The plate is driven by a point force at its center and the positions of the masses are prescribed. The structural vibration problem is solved using a simple Rayleigh-Ritz approach. Solving the acoustic radiation problem is simplified by making a low-ka-assumption, i.e., the point masses are determined so as to minimize the surface volume velocity of the plate. The predicted results are verified experimentally by means of sound intensity measurements. It is shown that a structural resonance can be deleted from the acoustic response by exploiting volume velocity cancellation. The effects involved are illustrated in detail.

Application of the Helmholtz Integral in Acoustics

1986 ◽  
Vol 108 (4) ◽  
pp. 447-453 ◽  
Author(s):  
M. A. Latcha ◽  
A. Akay
Keyword(s):  
Acoustic Radiation ◽  
Surface Element ◽  
Sound Power ◽  
Acoustic Response ◽  
Element Size ◽  
Radiated Sound ◽  
Radiated Sound Power ◽  
Helmholtz Integral

The solution of an isoparametric, overdetermined formulation of the Helmholtz Integral is presented and demonstrated in three examples of acoustic radiation from spherical sources. The placement of the interior, overdetermining points is discussed and guidelines concerning surface element size are developed and tested. The total radiated sound power and transient acoustic response of a dilating sphere are computed.

USE OF GROOVED SURFACES TO IMPROVE HYDRODYNAMIC, CAVITATION AND ACOUSTIC CHARACTERISTICS OF WINGS AND ELEMENTS OF VANE PROPULSION SYSTEMS (REVIEW)

2021 ◽  
Vol 2 ◽  
pp. 3-17
Author(s):  
A.L. SUKHORUKOV
Keyword(s):  
Computational Models ◽  
Acoustic Radiation ◽  
Hydrodynamic Cavitation ◽  
Propulsion Systems ◽  
Acoustic Characteristics ◽  
Flow Parameters ◽  
Turbulent Transition ◽  
Grooved Surface ◽  
Propeller Blades ◽  
Laminar Turbulent Transition

The paper reviews the use of grooved surfaces and sawtooth (chevron) edges to control the flow parameters of the wings, propeller blades and elements of vane propulsion systems operating in both gaseous and liquid media. Particular attention is paid to the physical mechanisms of improving the hydrodynamic, cavitation and acoustic characteristics under the influence of a grooved surface. These mechanisms are associated with a change in the flow structure in the region of the laminar-turbulent transition, the peculiarities of the occurrence of cavitation and acoustic radiation in the region of the outgoing edges. The results of the verification of computational models describing the behavior of the flow taking into account the laminar-turbulent transition, the use of which is necessary for studying flows near a grooved surface, are presented.

Dipole strength distribution ofGe74

2015 ◽  
Vol 92 (4) ◽  
Author(s):  
R. Massarczyk ◽  
R. Schwengner ◽  
L. A. Bernstein ◽  
M. Anders ◽  
D. Bemmerer ◽  
...  
Keyword(s):  
Strength Distribution ◽  
Dipole Strength

Acoustic Radiation Simulation of Marine Sliding-Thrust Bearing Shell Based on SYSNOISE

2011 ◽  
Vol 291-294 ◽  
pp. 1961-1964
Author(s):  
Guang Liang Zhao
Keyword(s):  
Dynamic Analysis ◽  
Boundary Element ◽  
Thrust Bearing ◽  
Acoustic Radiation ◽  
Element Model ◽  
Sound Power ◽  
Supporting Structure ◽  
Radiated Sound ◽  
The Impact ◽  
Radiated Sound Power

This paper takes marine Kingsbury sliding thrust bearing as the research object and conducts the finite element dynamic analysis with the aid of ANSYS software. On this basis, the acoustic boundary element model of a sliding thrust bearing shell is established with the ANSYS dynamic analysis results as the boundary excitation conditions. Besides, the radiated sound power of the shell is calculated by indirect boundary element method in SYNOSISE software. The influence of different condition parameters on the radiated sound power of the shell is perceived through the analysis of several rotation-thrust conditions. As for the special structure of this kind of sliding-thrust bearing, this paper states the impact of the supporting structure performance parameters, the pad number and damp of shell on the shell radiated sound power. The optimized measure for the supporting structure and the plan concerning the pad number’s selection lays the theoretical basis for damping and noise-reducing research on marine sliding-thrust bearing and its rotor system.

scholarly journals Magnetic dipole strength distribution at high excitation energies in deformed nuclei

1989 ◽  
Vol 220 (3) ◽  
pp. 351-355 ◽  
Author(s):  
K.-G. Dietrich ◽  
F. Humbert ◽  
A. Richter ◽  
B.A. Brown ◽  
A.A. Kuliev ◽  
...  
Keyword(s):  
Magnetic Dipole ◽  
Strength Distribution ◽  
High Excitation ◽  
Dipole Strength ◽  
Excitation Energies ◽  
Deformed Nuclei

Genetic Algorithms for the Vibroacoustic Optimization of the Thin Parts of I.C. Engine

2003 ◽  
Author(s):  
Xiaolong Deng ◽  
Zongjie Zhang ◽  
Chunpeng Sun ◽  
Shaohe Li
Keyword(s):  
Noise Level ◽  
Numerical Optimization ◽  
Acoustic Power ◽  
Single Frequency ◽  
Acoustic Response ◽  
Promising Tool ◽  
Specific Frequency ◽  
Radiated Sound ◽  
Noise Vibration ◽  
Radiated Sound Power

The Noise Vibration Harshness (NVH) behavior of engines is one of the predominant factors for market acceptance of vehicles. To reach this goal it is necessary to reduce the absolute noise level and also the noise level in specific frequency ranges. The design of radiating structures for minimal sound radiation is a multidisciplinary problem that involves complex objective functions and expensive computations. In this paper, genetic algorithm is used as a promising tool for numerical optimization of such problems. The objective of the study is to determine effective, general design methods for determining the optimal design of thin parts of I.C. engine that minimizes the total radiated acoustic power. Variable attached discrete masses are considered. Acoustic response is minimized either at a single frequency or first five natural frequencies. Radiated sound power is calculated using a boundary element method, in conjunction with a finite element solver ANSYS for the solution of the structural acoustical problem.

scholarly journals Microscopic description of the pygmy dipole resonance in neutron-rich Ca isotopes

2018 ◽  
Vol 194 ◽  
pp. 04002
Author(s):  
N.N. Arsenyev ◽  
A.P. Severyukhin ◽  
V.V. Voronov ◽  
N.V. Giai
Keyword(s):  
Electric Dipole ◽  
Random Phase Approximation ◽  
Strength Function ◽  
Random Phase ◽  
Strength Distribution ◽  
Low Energy ◽  
Dipole Strength ◽  
Quasiparticle Random Phase Approximation ◽  
Dipole Resonance ◽  
Dipole Response

We study the effects of the phonon-phonon coupling on the low-energy electric dipole response within a microscopic model based on an effective Skyrme interaction. The finite rank separable approach for the quasiparticle random phase approximation is used. Choosing as an example the isotopic chain of Calcium, we show the ability of the method to describe the low-energy E1 strength distribution. With one and the same set of parameters we describe available experimental data for 48Ca and predict the electric dipole strength function for 50Ca.

A compact active structural acoustic control method for minimizing radiated sound power

2021 ◽  
Vol 263 (3) ◽  
pp. 3396-3406
Author(s):  
Scott Sommerfeldt
Keyword(s):  
Control Method ◽  
Acoustic Radiation ◽  
Structural Vibration ◽  
Sound Power ◽  
Flat Plates ◽  
Spatial Gradients ◽  
Acoustic Control ◽  
Radiated Sound ◽  
Radiated Sound Power ◽  
Structural Acoustic Control

Active structural acoustic control is an active control method that controls a vibrating structure in a manner that reduces the sound power radiated from the structure. Such methods focus on attenuating some metric that results in attenuated sound power, while not necessarily minimizing the structural vibration. The work reported here outlines the weighted sum of spatial gradients (WSSG) control metric as a method to attenuate structural radiation. The WSSG method utilizes a compact error sensor that is able to measure the acceleration and the acceleration gradients at the sensor location. These vibration signals are combined into the WSSG metric in a manner that is closely related to the radiated sound power, such that minimizing the WSSG also results in a minimization of the sound power. The connection between WSSG and acoustic radiation modes will be highlighted. Computational and experimental results for both flat plates and cylindrical shells will be presented, indicating that the WSSG method can achieve near optimal attenuation of the radiated sound power with a minimum number of sensors.

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