An Arnoldi Based Projection Formulation for Fully Coupled Low Frequency Structural-Acoustic Analysis

2011 ◽  
Vol 97 (3) ◽  
pp. 509-518 ◽  
Author(s):  
R. Srinivasan Puri ◽  
Denise Morrey
Keyword(s):  
Acoustic Analysis ◽  
Low Frequency ◽  
Fully Coupled

On the Accuracy of Dynamic and Acoustic Analysis of Lightweight Panel Structures: A Comparison of ABAQUS and ANSYS

2012 ◽  
Author(s):  
Poul Henning Kirkegaard ◽  
Lars Vabbersgaard Andersen ◽  
Kristoffer Ahrens Dickow
Keyword(s):  
Acoustic Analysis ◽  
Low Frequency ◽  
Coupled Model ◽  
Acoustic Medium ◽  
Building Structures ◽  
Sound Waves ◽  
Frequency Range ◽  
Element Analysis ◽  
Structural Part ◽  
Fully Coupled

During the last couple of years, there has been an increasing focus on the vibro-acoustic performance of built environments due to increasing requirements in building codes regarding impact and airborne sound transmission. Hence, development of efficient and accurate methods for prediction of sound in such buildings is important. In the low-frequency range, prediction of sound and vibration in building structures may be achieved by finite-element analysis (FEA). The aim of this paper is to compare the two commercial codes ABAQUS and ANSYS for FEA of an acoustic-structural coupling in a timber, lightweight panel structure. For this purpose, modal analyses are carried out employing a fully coupled model of sound waves within an acoustic medium and vibrations in the structural part. The study concerns the frequency range 50–250 Hz.

scholarly journals Flow around an inclined circular disk

2018 ◽  
Vol 851 ◽  
pp. 687-714 ◽  
Author(s):  
Song Gao ◽  
Longbin Tao ◽  
Xinliang Tian ◽  
Jianmin Yang
Keyword(s):  
Low Frequency ◽  
Circular Disk ◽  
Streamwise Direction ◽  
Chaotic State ◽  
Dominant Position ◽  
Periodic State ◽  
Flow Features ◽  
Fluid Body ◽  
Planar Symmetry ◽  
Fully Coupled

Direct numerical simulations are performed for the uniform flow around an inclined circular disk. The diameter–thickness aspect ratio ($\unicode[STIX]{x1D712}=D/t_{d}$) of the disk is 50 and the inclination angle ($\unicode[STIX]{x1D6FC}$) is considered over the range of $0^{\circ }\leqslant \unicode[STIX]{x1D6FC}\leqslant 80^{\circ }$, where $\unicode[STIX]{x1D6FC}=0^{\circ }$ refers to the condition where the flow is normal to the disk. The Reynolds number ($\mathit{Re}$), based on the short axis of projection in the streamwise direction, is defined as $\mathit{Re}=U_{\infty }D\cos \unicode[STIX]{x1D6FC}/\unicode[STIX]{x1D708}$, where $U_{\infty }$ is the velocity of the flow and $\unicode[STIX]{x1D708}$ is the kinematic viscosity. $\mathit{Re}$ is investigated over the range of 50 ${\leqslant}\mathit{Re}\leqslant$ 300. In the considered $\mathit{Re}$–$\unicode[STIX]{x1D6FC}$ parametric space, five states are observed and denoted as: (I) steady state (SS); (II) periodic state (PS); (III) periodic state with a low frequency modulation (PSL); (IV) quasi-periodic state (QP) and (V) chaotic state (CS). Both $\mathit{Re}$ and $\unicode[STIX]{x1D6FC}$ affect the bifurcation mechanism. The bifurcating sequence occurring at $\unicode[STIX]{x1D6FC}=0^{\circ }$ is generally observed over the whole $\mathit{Re}$–$\unicode[STIX]{x1D6FC}$ space, although it is advanced at small $\unicode[STIX]{x1D6FC}$ and delayed at large $\unicode[STIX]{x1D6FC}$. The advancement of thresholds for different states is due to the effects introduced by inclination, which tend to select the plane of symmetry for the wake in order to regulate the wake and intensify some flow features. Nevertheless, the bifurcations are still in the dominant position when leading a state without stable symmetry, i.e. the planar symmetry could not be recovered by small $\unicode[STIX]{x1D6FC}$. These phenomena are further discussed with respect to the vortex shedding patterns behind the disk. Furthermore, for any fixed disk, the wake behaviour is only associated with that found in the steady vertical state of a freely falling disk. The fully coupled fluid–body system is fundamentally different from the fixed cases.

Nonlinear Analysis of Dynamic Responses of a MOSES TLP in Extreme Conditions

2015 ◽  
Author(s):  
Fasuo Yan ◽  
Hui Yang ◽  
Liping Sun ◽  
Dagang Zhang
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Time Domain Analysis ◽  
Dynamic Responses ◽  
Wave Forces ◽  
Environmental Load ◽  
Hydrodynamic Efficiency ◽  
Nonlinear Responses ◽  
Heave Motion ◽  
Fully Coupled

The configuration of MOSES TLP is quite different from conventional types. A compact central columns group and extended tendon support structure provides better deck support and hydrodynamic efficiency. A fully-coupled time domain analysis was adopted to evaluate effects of first and second order wave forces, motions and tendon tensions in hurricane conditions. The nonlinear responses due to the environmental load and interaction between the hull and tendons that includes large surge-heave motion in the low frequency and resonant heave/pitch responses with the spring loads in the high frequency are focused on in the paper. Results from numerical simulation are compared with data in full scale measurement.

Investigation of frequency dependent mechanical properties of porous materials using dynamic mechanical analyzer and frequency-temperature superposition theory

2021 ◽  
Vol 263 (2) ◽  
pp. 4851-4862
Author(s):  
Attila Schweighardt ◽  
Balazs Vehovszky
Keyword(s):  
Frequency Dependence ◽  
Storage Modulus ◽  
Acoustic Analysis ◽  
Fluid Motion ◽  
Low Frequency ◽  
Dynamic Mechanical Analyzer ◽  
Dynamic Mechanical ◽  
Frequency Measurements ◽  
Temperature Superposition ◽  
Frequency Temperature

In acoustic design of engineering applications - such as in the acoustic analysis of passenger vehicles - poroelastic materials are of great importance. One of the most influencing properties in determining their noise-reduction potential is the storage modulus. The purpose of this study is to examine the frequency dependence of storage modulus of selected porous acoustic materials at least up to 1000 Hz. This is executed by using the combined use of dynamic mechanical analyzer and frequency-temperature superposition theory. All other methods for measuring the storage modulus fall short in determining frequency-dependence above 100 Hz: quasi-static mechanical analyzer is mostly used for determining an averaged constant value deduced from low-frequency measurements, while the usage of an electromagnetic shaker capable for high-frequency excitation may include effects of fluid motion inside the pores, thus significantly modifying the results. Frequency-temperature superposition enables to determine the storage modulus values in a wide frequency range, based on low-frequency measurements, where fluid-structure interaction is negligible. It was found that the modulus varied significantly up to and beyond 1000 Hz, and thus, acoustical characterization of these materials can be significantly improved using the proposed method. The work concludes with recommendations to improve the accuracy of the results.

Fluctuating Pressure Generating in BWR Main Steam Lines Acoustic Excited by Safety Relief Valve Stub Pipes and Dead Legs

2010 ◽  
Author(s):  
Shiro Takahashi ◽  
Keita Okuyama ◽  
Akinori Tamura ◽  
Masaya Ohtsuka ◽  
Masaaki Tsubaki ◽  
...  
Keyword(s):  
Flow Velocity ◽  
High Frequency ◽  
Acoustic Analysis ◽  
Low Frequency ◽  
Sound Field ◽  
Acoustic Resonance ◽  
Operating Conditions ◽  
Relief Valve ◽  
Fluctuating Pressure ◽  
Main Steam

During operation, the BWR-3 steam dryer in the Quad Cities Unit 2 Nuclear Power Plant was damaged by high cycle fatigue. The dryer failure was attributed to flow-induced acoustic resonance at the stub pipes of safety relief valves (SRVs) in the main steam lines (MSLs). The acoustic resonance was considered to be generated by interaction between the sound field and an unstable shear layer across the closed side branches with SRV stub pipes. We HITACHI and CRIEPI have started a research program on BWR dryers to develop their loading evaluation methods. Moreover, it has become necessary to evaluate the dryer integrity of BWR-5 plants in particular which are the main type of BWR in Japan. In the present study, we used 1/10-scale BWR tests and analyses to investigate the flow-induced acoustic resonance and characteristics of fluctuating pressure in MSLs. The test apparatus consisted of a steam dryer, a steam dome and 4 MSLs with 20 SRV stub pipes. A finite element method (FEM) was applied for the calculation of three-dimensional wave equations in acoustic analysis. We demonstrated that remarkable fluctuating pressures occurred in high and low frequency regions. Intensity of three peaks observed in the spectrum of fluctuating pressure in MSLs was increased with St. High frequency fluctuating pressures were generated by the flow-induced acoustic resonance in the SRV stub pipes. Low frequency fluctuating pressures were excited by the acoustic resonance in the dead leg. Frequency of fluctuating pressure generating in the SRV stub pipe was changed with St. On the other hand, frequency of fluctuating pressure excited by dead leg was almost constant. Fluctuating pressure in low frequency range increased gradually with flow velocity and its intensity was roughly proportional to the square of flow velocity. The flow-induced acoustic resonance did not occur for St larger than 0.6 in the BWR MSLs for both low and high frequency ranges. Operating conditions of the BWR-5 from 100 to 115% were in the range of St larger than 0.6, so intense acoustic resonance would not occur in the BWR MSLs.

scholarly journals Reduced order fully coupled structural–acoustic analysis via implicit moment matching

2009 ◽  
Vol 33 (11) ◽  
pp. 4097-4119 ◽  
Author(s):  
R. Srinivasan Puri ◽  
Denise Morrey ◽  
Andrew J. Bell ◽  
John F. Durodola ◽  
Evgenii B. Rudnyi ◽  
...  
Keyword(s):  
Acoustic Analysis ◽  
Moment Matching ◽  
Reduced Order ◽  
Fully Coupled

Quantitative measurement of depression through speech analysis

1994 ◽  
Vol 9 (4) ◽  
pp. 185-193 ◽  
Author(s):  
JA Talavera ◽  
J Sáiz-Ruiz ◽  
M García-Toro
Keyword(s):  
Cognitive Processing ◽  
Acoustic Analysis ◽  
Reaction Times ◽  
Low Frequency ◽  
Reliability And Validity ◽  
Normal Subjects ◽  
Spectral Energy ◽  
Normal Individuals ◽  
Quantitative Indicators ◽  
Different Levels

SummaryLooking for a substantial increase in the reliability and validity of voice analysis measurements in depression, we have developed a new experimental paradigm. The paradigm is based on two vocal tasks with different levels of cognitive processing and a baseline verbal task. It has been applied to 40 subjects, 20 patients with affective disorders and 20 normal individuals. We have found that an important set of vocal parameters, at different intervals, discriminates patients from normal subjects. Here, we discuss four of them – those that have been especially consistent; the patients had longer reaction times, a higher proportion of relative spectral energy (at a very low frequency band), narrower fundamental frequency range and higher proportion of omissions. Under the proposed paradigm, the acoustic analysis could be a promising instrument for the development of quantitative indicators of depression.

Acoustic analyses of potential vocalization in lambeosaurine dinosaurs (Reptilia: Ornithischia)

Paleobiology ◽  
1981 ◽  
Vol 7 (2) ◽  
pp. 252-261 ◽  
Author(s):  
David B. Weishampel
Keyword(s):  
Nasal Cavity ◽  
Acoustic Analysis ◽  
Vocal Communication ◽  
Low Frequency ◽  
Cavity Size ◽  
High Frequencies ◽  
Acoustic Analyses ◽  
Auditory Acuity ◽  
Selection For ◽  
High Degree

Lambeosaurine dinosaur crests are judged to have been conducive to resonation on the basis of an acoustic analysis of the structure of the nasal cavity. Size and shape of the nasal cavity suggest low vocal frequencies in adults, as does information on potential auditory acuity in these animals. Lateral diverticula (present in all but juvenile specimens) acted to suppress portions of the vocal spectrum. Juveniles vocalized at higher frequencies than adults and potential auditory sensitivity at high frequencies in adults suggests a high degree of parent-offspring vocal communication. Sexual variation and causes of selection for low frequency vocalization are also examined.

Sign in / Sign up

Export Citation Format

Share Document