A MODIFIED INFINITE ELEMENT METHOD FOR ACOUSTIC RADIATION

2002 ◽  
Vol 10 (01) ◽  
pp. 113-121 ◽  
Author(s):  
L.-X. LI ◽  
J.-S. SUN ◽  
H. SAKAMOTO
Keyword(s):  
Finite Element ◽  
Boundary Conditions ◽  
Governing Equation ◽  
Sound Pressure ◽  
Acoustic Radiation ◽  
Infinite Element ◽  
Relative Boundary ◽  
Infinite Element Method ◽  
Finite Element Meshes ◽  
Element Method

An infinite element method is proposed to help solve practical problems in engineering and extend the applicability of infinite element. Based on the Helmholtz's equation, a novel governing equation is derived in terms of the modified sound pressure. The relative boundary conditions are established and the system matrices in using the combination of conventional finite element and new infinite element are subsequently formed. As a result, the use of coarser finite element meshes is permitted for a given frequency. The effectiveness and accuracy of this method are demonstrated in application to two typical examples.

Vibration Analysis of a Shell Structure by Finite Element Method

2012 ◽  
Vol 591-593 ◽  
pp. 1929-1933
Author(s):  
Ming Hui Zhao
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Vibration Frequency ◽  
Shell Structure ◽  
Sound Pressure ◽  
Acoustic Radiation ◽  
Spherical Shells ◽  
Fluid Medium ◽  
Modes Of Vibration ◽  
Element Method

Plate-shell structures, especially cylindrical shells and spherical shells, are widely used in engineering fields, such as aircraft and tanks, missiles, submarines, ships, hydraulic pumps, infusion pipelines and gas pipelines, and so on. These structures are usually in a fluid medium, which are related to the structure fluid-solid coupling and acoustic radiation field. As many experiments show that enclosed air in a thin walled structure, just like the violin, affects some modes of vibration significantly, air coupling between vibrating sides of the structure cannot be neglected. In order to explore the sound pressure distribution of vibrational frequencies, this paper, considering the material anisotropy, analyzes a typical complex shell structure of the violin by finite element method, including acoustic-structure coupling analysis and post-processing, especially sound pressure vibration frequency extraction. Finally, we get the conclusion that the distribution of sound pressure vibration frequency is similar to the normal distribution.

Condition Number of Acoustic Infinite Element

2011 ◽  
Vol 181-182 ◽  
pp. 926-931 ◽  
Author(s):  
Rui Liang Yang ◽  
Cai Xia Zhu
Keyword(s):  
Finite Element ◽  
Condition Number ◽  
Shape Function ◽  
Unbounded Domains ◽  
Research Literature ◽  
Bounded Domains ◽  
Node Number ◽  
Infinite Element ◽  
Infinite Element Method ◽  
Element Method

Various shape function and weight function of infinite element are researched and summarized into eight methods, and then various infinite element methods can be summarized as general equation, the condition number of which can reflect merits of infinite method. Condition number of various methods versus frequency and the node number are calculated in this paper. Finally, most optimal infinite element method is summed up. The infinite element method [1-12] is among the most successful techniques used to solve boundary-value problems on unbounded domains and whose solutions satisfy some condition at infinity. Two ideas make the infinite element method attractive: the idea of partition and the idea of approximation. The partition idea covers unbounded domains by attaching infinite strips to finite element partitions of bounded domains. More mature versions of infinite element method involved the approximation idea. These ideas make it possible that the finite element/infinite element method yields significantly greater computational efficiency than other methods such as the boundary element method. There have been a large number of infinite element methods, in which some methods have obvious advantages and some methods have fewer advantages. However, there is less research literature about merits of various infinite element methods appear at home and abroad. Thus, condition number of matrix equation is applied to verify merits of various infinite methods in this paper.

Application of the Boundary Element Method and Modal Analysis to Tire Acoustics Problems

1993 ◽  
Vol 21 (2) ◽  
pp. 66-90 ◽  
Author(s):  
Y. Nakajima ◽  
Y. Inoue ◽  
H. Ogawa
Keyword(s):  
Finite Element ◽  
Boundary Element Method ◽  
Boundary Element ◽  
Acoustic Radiation ◽  
Traffic Noise ◽  
Noise Prediction ◽  
Prediction System ◽  
Tire Noise ◽  
Acoustic Contribution ◽  
Element Method

Abstract Road traffic noise needs to be reduced, because traffic volume is increasing every year. The noise generated from a tire is becoming one of the dominant sources in the total traffic noise because the engine noise is constantly being reduced by the vehicle manufacturers. Although the acoustic intensity measurement technology has been enhanced by the recent developments in digital measurement techniques, repetitive measurements are necessary to find effective ways for noise control. Hence, a simulation method to predict generated noise is required to replace the time-consuming experiments. The boundary element method (BEM) is applied to predict the acoustic radiation caused by the vibration of a tire sidewall and a tire noise prediction system is developed. The BEM requires the geometry and the modal characteristics of a tire which are provided by an experiment or the finite element method (FEM). Since the finite element procedure is applied to the prediction of modal characteristics in a tire noise prediction system, the acoustic pressure can be predicted without any measurements. Furthermore, the acoustic contribution analysis obtained from the post-processing of the predicted results is very helpful to know where and how the design change affects the acoustic radiation. The predictability of this system is verified by measurements and the acoustic contribution analysis is applied to tire noise control.

scholarly journals Shape Sensing of a Complex Aeronautical Structure with Inverse Finite Element Method

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1388
Author(s):  
Daniele Oboe ◽  
Luca Colombo ◽  
Claudio Sbarufatti ◽  
Marco Giglio
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Boundary Conditions ◽  
Strain Field ◽  
Element Analysis ◽  
Inverse Finite Element Method ◽  
Shape Sensing ◽  
Definition Of ◽  
High Level ◽  
Element Method

The inverse Finite Element Method (iFEM) is receiving more attention for shape sensing due to its independence from the material properties and the external load. However, a proper definition of the model geometry with its boundary conditions is required, together with the acquisition of the structure’s strain field with optimized sensor networks. The iFEM model definition is not trivial in the case of complex structures, in particular, if sensors are not applied on the whole structure allowing just a partial definition of the input strain field. To overcome this issue, this research proposes a simplified iFEM model in which the geometrical complexity is reduced and boundary conditions are tuned with the superimposition of the effects to behave as the real structure. The procedure is assessed for a complex aeronautical structure, where the reference displacement field is first computed in a numerical framework with input strains coming from a direct finite element analysis, confirming the effectiveness of the iFEM based on a simplified geometry. Finally, the model is fed with experimentally acquired strain measurements and the performance of the method is assessed in presence of a high level of uncertainty.

Physical statement of the problem for a numerical model of soil freezing and heaving taking into account heat and mass transfer

2021 ◽  
pp. 244-256
Author(s):  
Виктор Григорьевич Чеверев ◽  
Евгений Викторович Сафронов ◽  
Алексей Александрович Коротков ◽  
Александр Сергеевич Чернятин
Keyword(s):  
Finite Element Method ◽  
Mass Transfer ◽  
Finite Element ◽  
Numerical Model ◽  
Boundary Conditions ◽  
Heat And Mass Transfer ◽  
Soil Freezing ◽  
The Finite Element Method ◽  
Freezing Front ◽  
Element Method

Существуют два основных подхода решения задачи тепломассопереноса при численном моделировании промерзания грунтов: 1) решение методом конечных разностей с учетом граничных условий (границей, например, является фронт промерзания); 2) решение методом конечных элементов без учета границ модели. Оба подхода имеют существенные недостатки, что оставляет проблему решения задачи для численной модели промерзания грунтов острой и актуальной. В данной работе представлена физическая постановка промерзания, которая позволяет создать численную модель, базирующуюся на решении методом конечных элементов, но при этом отражающую ход фронта промерзания - то есть модель, в которой объединены оба подхода к решению задачи промерзания грунтов. Для подтверждения корректности модели был проделан ряд экспериментов по физическому моделированию промерзания модельного грунта и выполнен сравнительный анализ полученных экспериментальных данных и результатов расчетов на базе представленной численной модели с такими же граничными условиями, как в экспериментах. There are two basic approaches to solving the problem of heat and mass transfer in the numerical modeling of soil freezing: 1) using the finite difference method taking into account boundary conditions (the boundary, for example, is the freezing front); 2) using the finite element method without consideration of model boundaries. Both approaches have significant drawbacks, which leaves the issue of solving the problem for the numerical model of soil freezing acute and up-to-date. This article provides the physical setting of freezing that allows us to create a numerical model based on the solution by the finite element method, but at the same time reflecting the route of the freezing front, i.e. the model that combines both approaches to solving the problem of soil freezing. In order to confirm the correctness of the model, a number of experiments on physical modeling of model soil freezing have been performed, and a comparative analysis of the experimental data obtained and the calculation results based on the provided numerical model with the same boundary conditions as in the experiments was performed.

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