Design of acoustic foam wedge panels by finite element frequency domain acoustical analysis

2019 ◽  
Vol 55 (3) ◽  
pp. 283-295
Author(s):  
Huoy-Shyi Tsay ◽  
Fung-Huei Yeh
Keyword(s):  
Finite Element ◽  
Numerical Method ◽  
Frequency Domain ◽  
Acoustic Field ◽  
High Frequency ◽  
Sound Absorption ◽  
Wedge Angle ◽  
Cross Sectional ◽  
Calculation Time ◽  
Acoustical Analysis

Acoustic foam wedge panels provide good sound absorption qualities in the mid and high frequency ranges. In this study, a finite element frequency domain acoustical analysis is used for analysis. Such a numerical method is more efficient than the earlier studies by saving the calculation time on the elements of the incident acoustic field. During the design of a wedge panel, the cross-sectional width and the area of one section of the wedge panel are kept the same throughout the study. By varying the wedge angle, the maximum sound absorption capability of the wedge foam can be found. It is concluded that in the interested frequency regions, 100–4000 and 2000–4000 Hz, the wedge foam with wedge angle of 31° has the excellent sound absorption capability.

Investigation of Effective Bending and Shear Stiffness of Thin-Walled Girders Related to Ship Hull Vibration Analysis

1989 ◽  
Vol 33 (04) ◽  
pp. 298-309
Author(s):  
Ivo Senjanovic ◽  
Ying Fan
Keyword(s):  
Finite Element ◽  
Frequency Domain ◽  
Vibration Analysis ◽  
Ship Hull ◽  
Moment Of Inertia ◽  
Cross Sectional ◽  
Simply Supported ◽  
Thin Walled ◽  
Beam Parameters ◽  
Shear Area

Application of beam theory in flexural vibration analysis of thin-walled girders is extended for the high-frequency domain by introducing the concept of effective values of beam parameters, that is, cross-sectional moment of inertia, shear area, mass, and mass moment of inertia. Formulation of these parameters is based on equivalence of deformation energy and inertia work, respectively, for a considered structure and its beam model, resulting in the same values of their natural frequencies. For illustration, the natural vertical vibration of a simply supported pontoon has been considered, where it was possible to obtain the analytical solution due to sinusoidal mode shapes. The effective values of cross-sectional moment of inertia and shear area show significant variation in frequency domain. Transfer of effective values of beam parameters, determined for simply supported structure, in the case of other boundary conditions is suggested, based on equal mode wavelengths, and checked for the free pontoon. The results show very low discrepancies compared with a three-dimensional finite-element model solution, so this procedure may be applied generally, as well as to the problem of ship hull vibration. In conclusion, the possibility of calculating the values of effective parameters for multicell ship cross sections, utilizing the theory of folded structure and the finite-element method, is pointed out.

On a structural–acoustic panel cavity modelling in the mid-high frequency domain

2011 ◽  
Vol 226 (4) ◽  
pp. 900-912 ◽  
Author(s):  
M de Rochambeau ◽  
M Ichchou ◽  
B Troclet
Keyword(s):  
Finite Element ◽  
Frequency Domain ◽  
High Frequency ◽  
Energy Analysis ◽  
Coupled System ◽  
Element Model ◽  
Statistical Energy Analysis ◽  
Hybrid Strategy ◽  
Interaction Modelling

This article presents a fluid–structure interaction modelling, based on a coupling between component mode synthesis or finite element and statistical energy analysis (SEA). The hybrid strategy is applied on a panel–cavity coupled system using a modal analysis with uncoupled modes of the subsystems and through a finite element model of the coupled system. The determination of the energy transfer parameters is then considered. The hybrid SEA model is then validated in the high-frequency domain by comparison with an SEA model. Finally, a parametric survey is offered through the established modelling and conclusions on its validity domain are drawn.

Synthesis and Simplification of Fractal Profile

2011 ◽  
Vol 279 ◽  
pp. 262-265
Author(s):  
Chao Zhou ◽  
Cheng Hui Gao ◽  
Jie Chen ◽  
Lian Feng Lai
Keyword(s):  
Finite Element ◽  
Fourier Transform ◽  
Frequency Domain ◽  
Discrete Fourier Transform ◽  
High Frequency ◽  
Space Domain ◽  
Finite Element Software ◽  
Redundant Data ◽  
Frequency Components

In order to import a synthesized fractal profile into finite element software, the profile synthesized by discrete Fourier transform was studied. The synthesized profile was filtered in frequency domain in order to filter its high frequency components and to make it smooth, and then the chord deviation algorithm was used to reduce its redundant data in space domain. It was found that: after filtering, the profile is smooth but with lots of redundant data; the chord deviation algorithm can simplify the profile which is redundant in space domain; the time needed in the process of importing a profile into finite element software can be reduced greatly after profile simplification.

High-Frequency Vibration Analysis of Thin Plate Based on B-Spline Wavelet on Interval Finite Element Method

2016 ◽  
Author(s):  
Jia Geng ◽  
Xingwu Zhang ◽  
Xuefeng Chen ◽  
Xiaofeng Xue
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Dynamic Analysis ◽  
Frequency Domain ◽  
Thin Plate ◽  
Finite Element Methods ◽  
High Frequency ◽  
Numerical Example ◽  
Modal Density ◽  
High Modal Density

For the dynamic analysis of thin plate bending problems, the Finite Element Methods (FEMs) are the most commonly used numerical techniques in engineering. However, due to the deficiency of low computing efficiency and accuracy, the FEMs can’t be directly used to effectively evaluate dynamic analysis of thin plate with high modal density within low-high frequency domain. In order to solve this problem, the Wavelet Finite Element Methods (WFEMs) has been introduced to solve the problem by improving the computing efficiency and accuracy in this paper. Due to the properties of multi-resolution, the WFEMs own excellently high computing efficiency and accuracy for structure analysis. Furthermore, for the destination of predicting dynamic response of thin plate within high frequency domain, this paper introduces the Multi-wavelet element method based on c1 type wavelet thin plate element and a new assembly procedure to significantly promote the calculating efficiency and accuracy which aim at breaking up the limitation of frequency domain when using the existing WFEMs and traditional FEMs. Besides, the numerical studies are applied to certify the validity of the method by predicting state response of thin plate within 0∼1000Hz based on a special numerical example with high modal density. According to the literature, the frequency domain between 0 to 1000Hz contains the low-high frequency domain aiming at the numerical example. The numerical results show excellent agreement with the reference solutions captured by FEM and analytical expressions respectively. Among these, it is noteworthy that the relative errors between the analytical solutions and numerical solution are less than 0.4% when the dynamic response involved with 1000 modes.

scholarly journals Vaccine-Related Errors in Reconstitution in South Korea: A National Physicians’ and Nurses’ Survey

Vaccines ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 117
Author(s):  
Young Hwa Lee ◽  
Rebecca C. Harris ◽  
Hong Won Oh ◽  
Yongho Oh ◽  
Juan C. Vargas-Zambrano ◽  
...  
Keyword(s):  
South Korea ◽  
High Frequency ◽  
Cross Sectional Study ◽  
Sectional Study ◽  
Cross Sectional ◽  
Vaccine Preparation

Vaccine-related errors (VREs) result from mistakes in vaccine preparation, handling, storage, or administration. We aimed to assess physicians’ and nurses’ experiences of VREs in South Korea, focusing on reconstitution issues, and to understand the barriers to and facilitators of preventing them. This was a cross-sectional study using an internet-based survey to examine experiences of reconstitution-related errors, and experience or preference with regard to ready-to-use vaccines (RTU) by physicians and nurses. A total of 700 participants, including 250 physicians and 450 nurses, responded to the questionnaire. In total, 76.4% and 41.5% of the physicians and nurses, respectively, reported an error related to reconstituted vaccines. All errors had been reported as experienced by between 4.9% and 52.0% of physicians or nurses. The errors were reported to occur in more than one in 100 vaccinations for inadequate shaking of vaccines by 28.0% of physicians and 6.9% of nurses, incomplete aspiration of reconstitution vials by 28.0% of physicians and 6.4% of nurses, and spillage or leakage during reconstitution by 20.8% of physicians and 6.9% of nurses. A total of 94.8% of physicians had experience with RTU vaccines, and all preferred RTU formulations. In conclusion, this study highlights the high frequency and types of reconstitution-related errors in South Korea. RTU vaccines could help reduce the time needed for preparation and reduce the risk of errors in South Korea.

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