Sound Radiation Response of a Rectangular Plate Having a Side Crack of Arbitrary Length, Orientation, and Position

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Tanmoy Bose ◽  
Amiya R. Mohanty
Keyword(s):  
Rectangular Plate ◽  
Ritz Method ◽  
Sound Radiation ◽  
Radiation Efficiency ◽  
Sound Power ◽  
Cracked Plate ◽  
Side Crack ◽  
Radiated Sound ◽  
Radiated Sound Power ◽  
Element Method

Here, sound radiation characteristics of a rectangular plate having a side crack of different crack lengths, orientations, and positions are studied considering clamped boundary conditions. First, a free and forced vibration response analysis of a cracked plate is done using the Ritz method. Orthogonal polynomials are used for faster convergence and some corner functions are used to generate the effect of a crack. Radiated sound power and radiation efficiency of the cracked plate are computed by the quadruple integration. A convergence test of radiation efficiency is carried out to fix the number of polynomials and corner functions in the analysis. It is found that the radiation efficiency and radiated sound power computed by the Ritz method are close to the same obtained from the boundary element method (BEM). The natural frequencies computed using the Ritz method are also found to be close to that obtained from the finite element method (FEM). The radiation efficiency curves of different modes are shown for a change in crack length, orientation and position. Finally, the variations of normalized sound power are shown to be due to a change in the crack parameters.

ENFORCING RECIPROCITY IN NUMERICAL ANALYSIS OF ACOUSTIC RADIATION MODES AND SOUND POWER EVALUATION

2012 ◽  
Vol 20 (03) ◽  
pp. 1250005 ◽  
Author(s):  
HERWIG PETERS ◽  
NICOLE KESSISSOGLOU ◽  
STEFFEN MARBURG
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Acoustic Radiation ◽  
Sound Power ◽  
Impedance Matrix ◽  
Radiated Sound ◽  
The Asymmetry ◽  
Power Evaluation ◽  
Radiated Sound Power ◽  
Element Method

By identifying the efficiently radiating acoustic radiation modes of a fluid loaded vibrating structure, the storage requirements of the acoustic impedance matrix for calculation of the sound power using the boundary element method can be greatly reduced. In order to compute the acoustic radiation modes, the impedance matrix needs to be symmetric. However, when using the boundary element method, it is often found that the impedance matrix is not symmetric. This paper describes the origin of the asymmetry of the impedance matrix and presents a simple way to generate symmetry. The introduction of additional errors when symmetrizing the impedance matrix must be avoided. An example is used to demonstrate the behavior of the asymmetry and the effect of symmetrization of the impedance matrix on the sound power. The application of the technique presented in this work to compute the radiated sound power of a submerged marine vessel is discussed.

Relation Between Structural Intensity-Based Scalars and Sound Radiation Using the Example of Plate-Rib Models

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Clarissa Schaal ◽  
Johannes Ebert ◽  
Joachim Bös ◽  
Tobias Melz
Keyword(s):  
Objective Function ◽  
Energy Flow ◽  
Vibrational Energy ◽  
Sound Radiation ◽  
Specific Region ◽  
Sound Power ◽  
Structural Intensity ◽  
Radiated Sound ◽  
Very High ◽  
Radiated Sound Power

The ability of the structural intensity (STI) to predict changes in the sound radiation of structures due to geometric modifications is investigated using the academic example of plate-rib models. All models consist of the same plate and are modified by attaching a rib, whose position, orientation, and length are varied. Various scalar quantities are derived from the STI and quantitatively compared to the equivalent radiated sound power (ERP) for each model. Based on this comparison the relation between the STI-based scalars and the ERP is studied to determine an STI-based scalar that can serve as the objective function for numerical structural optimizations. The influence of the rib parameters on the most promising STI-based scalar is analyzed by means of a variance-based sensitivity analysis. The STI pattern of those models with very high and very low ERP values are additionally analyzed to describe the characteristics of STI. The results of this study indicate that the STI pattern of models with low ERP has paths and vortices that can be more clearly identified compared to those in models with high ERP. The angular orientation of the rib has by far the highest influence on changes in STI and ERP. The results reveal a correlation between the energy flow into a specific region of a structure, an STI-based scalar, and the ERP. Therefore, the vibrational energy flow can indeed serve as an objective function for numerical structural optimizations aiming at reducing the sound radiation.

Effect of In-Plane Forces on Sound Radiation From Convected, Fluid Loaded Plates

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Peter L. Schmidt ◽  
Kenneth D. Frampton
Keyword(s):  
Acoustic Radiation ◽  
Sound Radiation ◽  
Radiation Efficiency ◽  
Theoretical Development ◽  
Sound Power ◽  
Flow Speeds ◽  
Modes Of Vibration ◽  
Radiated Sound ◽  
Sound Radiation Efficiency ◽  
Power Radiation

The purpose of this work is to study the effects that plane stress has on the acoustic radiation from structures subjected to convected fluid loading. It is well established that fluid flow can have significant effects on structural acoustic behavior, along with the fact that induced coupling between discrete modes of vibration becomes significant as flow velocity increases. Work in this area has been confined to flows in air, over unloaded structures, with the effects on sound radiation efficiency, kinetic energy, and sound power radiation quantified and compared for various flow speeds. Theoretical development of the equations governing the vibration of a simply-supported plate subjected to in-plane forces in an infinite baffle and a semi-infinite flowing medium is presented along with a method for coupling these systems. Computational results are presented illustrating the effect of coupling on the sound power radiated from the plate in both subsonic and supersonic flows, for a variety of stress loading cases. It is shown that the state of stress in the plate affects the radiation efficiency of the plate, and that increasing stress eliminates a frequency shift in radiated sound power shown to exist for both subsonic and supersonic flow in previous work.

scholarly journals Sound Radiation Characteristics of a Rectangular Duct with Flexible Walls

2016 ◽  
Vol 2016 ◽  
pp. 1-15
Author(s):  
Praveena Raviprolu ◽  
Nagaraja Jade ◽  
Venkatesham Balide
Keyword(s):  
Analytical Model ◽  
Power Level ◽  
Sound Radiation ◽  
Rectangular Duct ◽  
Radiation Characteristics ◽  
Vibration Displacement ◽  
Flexible Walls ◽  
Radiated Sound ◽  
Radiated Sound Power ◽  
Element Method

Acoustic breakout noise is predominant in flexible rectangular ducts. The study of the sound radiated from the thin flexible rectangular duct walls helps in understanding breakout noise. The current paper describes an analytical model, to predict the sound radiation characteristics like total radiated sound power level, modal radiation efficiency, and directivity of the radiated sound from the duct walls. The analytical model is developed based on an equivalent plate model of the rectangular duct. This model has considered the coupled and uncoupled behaviour of both acoustic and structural subsystems. The proposed analytical model results are validated using finite element method (FEM) and boundary element method (BEM). Duct acoustic and structural modes are analysed to understand the sound radiation behaviour of a duct and its equivalence with monopole and dipole sources. The most efficient radiating modes are identified by vibration displacement of the duct walls and for these the radiation efficiencies have been calculated. The calculated modal radiation efficiencies of a duct compared to a simple rectangular plate indicate similar radiation characteristics.

scholarly journals An Adjoint Operator Approach for Sensitivity Analysis of Radiated Sound Power in Fully Coupled Structural-Acoustic Systems

2017 ◽  
Vol 25 (01) ◽  
pp. 1750003 ◽  
Author(s):  
Leilei Chen ◽  
Steffen Marburg ◽  
Haibo Chen ◽  
Hao Zhang ◽  
Hongbo Gao
Keyword(s):  
Sensitivity Analysis ◽  
Adjoint Operator ◽  
Design Sensitivity ◽  
Sound Power ◽  
Operator Approach ◽  
Design Variables ◽  
Structural Density ◽  
Radiated Sound ◽  
Radiated Sound Power ◽  
Element Method

Full interaction between structural and fluid domains must be considered for light structures immersed in heavy fluid (e.g. thin steel shells in water). The structural-acoustic design sensitivity analysis provides information on the effect of the design variable on acoustic performance, which makes it a key step for noise control and structural-acoustic optimization. This study uses the finite element method (FEM) to model the structure domain, while the fast multipole boundary element method (BEM) is applied to the exterior acoustic domain. An adjoint operator approach is developed to calculate the sensitivity of the radiated sound power with respect to the design variables, which can be any structural or fluid parameter (e.g. fluid or structural density, Poisson’s ratio, Young’s modulus, and geometric measures). Numerical examples are presented to demonstrate the validity and efficiency of the proposed algorithm.

scholarly journals Faster Calculation of the Low-Frequency Radiated Sound Power of Underwater Slender Cylindrical Shells

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Rui Tang ◽  
He Tian ◽  
Dajing Shang
Keyword(s):  
Cylindrical Shell ◽  
Cylindrical Shells ◽  
Low Frequency ◽  
Sound Radiation ◽  
Sound Power ◽  
Radiation Characteristics ◽  
Calculation Process ◽  
Radiated Sound ◽  
Stiffened Cylindrical Shells ◽  
Radiated Sound Power

Based on the fact that beam-type modes play the main role in determining the sound radiation from an underwater thin slender (length-to-radius ratio L/a>20) elastic cylindrical shell, an equivalent-beam method is proposed for calculating the low-frequency radiated sound power of underwater thin slender unstiffened and stiffened cylindrical shells. The natural bending frequencies of the cylindrical shell are calculated by analytical and numerical methods and used to solve equivalent Young’s modulus of the equivalent beam. This approach simplifies the vibration problem of the three-dimensional cylindrical shell into that of a two-dimensional beam, which can be used to simplify the calculation process of radiated sound power. Added mass is used to approximate the fluid-structure coupling, further simplifying the calculation process. Calculation examples of underwater simply supported unstiffened and stiffened cylindrical shells verify the proposed method by comparison with analytical and numerical results. Finally, the effects of the size and spacing of the stiffeners on the sound radiation characteristics of underwater free-free stiffened cylindrical shells are discussed. The proposed method can be extended to the rapid calculation of the sound radiation characteristics of underwater slender complex cylindrical shells in the low-frequency range.

scholarly journals A Comparison of Vibroacoustic Response of Isotropic Plate with Attached Discrete Patches and Point Masses Having Different Thickness Variation with Different Taper Ratios

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Bipin Kumar ◽  
Vinayak Ranjan ◽  
Mohammad Sikandar Azam ◽  
Piyush Pratap Singh ◽  
Pawan Mishra ◽  
...  
Keyword(s):  
Power Level ◽  
Low Frequency ◽  
Sound Radiation ◽  
Radiation Efficiency ◽  
Thickness Variation ◽  
Sound Power ◽  
Sound Power Level ◽  
Radiation Behavior ◽  
Thickness Variations ◽  
Different Thickness

A comparison of sound radiation behavior of plate in air medium with attached discrete patches/point masses having different thickness variations with different taper ratio of 0.3, 0.6, and 0.9 is analysed. Finite element method is used to find the vibration characteristics while Rayleigh integral is used to predict the sound radiation characteristics. Minimum peak sound power level obtained is at a taper ratio of 0.6 with parabolic increasing-decreasing thickness variation for plate with four discrete patches. At higher taper ratio, linearly increasing-decreasing thickness variation is another alternative for minimum peak sound power level suppression with discrete patches. It is found that, in low frequency range, average radiation efficiency remains almost the same, but near first peak, four patches or four point masses cause increase in average radiation efficiency; that is, redistribution of point masses/patches does have effect on average radiation efficiency at a given taper ratio.

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