scholarly journals Spiral Sound Wave Transducer Based on the Longitudinal Vibration

Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 3674 ◽  
Author(s):  
Wei Lu ◽  
Yu Lan ◽  
Rongzhen Guo ◽  
Qicheng Zhang ◽  
Shichang Li ◽  
...  
Keyword(s):  
Sound Wave ◽  
Longitudinal Vibration ◽  
Three Dimensional ◽  
Low Frequency ◽  
Sound Field ◽  
Field Measurements ◽  
Sound Waves ◽  
Underwater Sound ◽  
Three Dimensional Finite Element ◽  
Wave Transducer

A spiral sound wave transducer comprised of longitudinal vibrating elements has been proposed. This transducer was made from eight uniform radial distributed longitudinal vibrating elements, which could effectively generate low frequency underwater acoustic spiral waves. We discuss the production theory of spiral sound waves, which could be synthesized by two orthogonal acoustic dipoles with a phase difference of 90 degrees. The excitation voltage distribution of the transducer for emitting a spiral sound wave and the measurement method for the transducer is given. Three-dimensional finite element modeling (FEM)of the transducer was established for simulating the vibration modes and the acoustic characteristics of the transducers. Further, we fabricated a spiral sound wave transducer based on our design and simulations. It was found that the resonance frequency of the transducer was 10.8 kHz and that the transmitting voltage resonance was 140.5 dB. The underwater sound field measurements demonstrate that our designed transducer based on the longitudinal elements could successfully generate spiral sound waves.

Interaction between Strong Sound Waves and Cloud Droplets: Theoretical Analysis

2021 ◽  
Author(s):  
Ying-Hui Jia ◽  
Fang-Fang Li ◽  
Kun Fang ◽  
Guang-Qian Wang ◽  
Jun Qiu
Keyword(s):  
Sound Wave ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Sound Field ◽  
Pressure Level ◽  
Velocity Variation ◽  
Time Range ◽  
Sound Waves ◽  
Cloud Droplets ◽  
Acoustic Frequency

AbstractRecently strong sound wave was proposed to enhance precipitation. The theoretical basis of this proposal has not been effectively studied either experimentally or theoretically. Based on the microscopic parameters of atmospheric cloud physics, this paper solved the complex nonlinear differential equation to show the movement characteristics of cloud droplets under the action of sound waves. The motion process of individual cloud droplet in a cloud layer in the acoustic field is discussed as well as the relative motion between two cloud droplets. The effects of different particle sizes and sound field characteristics on particle motion and collision are studied to analyze the dynamic effects of thunder-level sound waves on cloud droplets. The amplitude of velocity variation has positive correlation with Sound Pressure Level (SPL) and negative correlation with the frequency of the surrounding sound field. Under the action of low-frequency sound waves with sufficient intensity, individual cloud droplets could be forced to oscillate significantly. The droplet smaller than 40μm can be easily driven by sound waves of 50 Hz and 123.4 dB. The calculation of the collision process of two droplets reveals that the disorder of motion for polydisperse droplets is intensified, resulting in the broadening of the collision time range and spatial range. When the acoustic frequency is less than 100Hz (@ 123.4dB) or the Sound Pressure Level (SPL) is greater than 117.4dB (@ 50Hz), the sound wave can affect the collision of cloud droplets significantly. This study provides theoretical perspective of acoustic effect to the microphysics of atmospheric clouds.

Non-Linear Dynamic Magneto Electric Effects in Ferromagnetic-Ferroelectric Layered Composites

2013 ◽  
Author(s):  
Satenik Harutyunyan ◽  
Davresh Hasanyan
Keyword(s):  
Vibration Frequency ◽  
Strain Distribution ◽  
Longitudinal Vibration ◽  
Three Dimensional ◽  
Low Frequency ◽  
Structure Design ◽  
Experimental Results ◽  
Physical Parameters ◽  
Wide Range ◽  
Non Linear

A non-linear theoretical model including bending and longitudinal vibration effects was developed for predicting the magneto electric (ME) effects in a laminate bar composite structure consisting of magnetostrictive and piezoelectric multi-layers. If the magnitude of the applied field increases, the deflection rapidly increases and the difference between experimental results and linear predictions becomes large. However, the nonlinear predictions based on the present model well agree with the experimental results within a wide range of applied electric field. The results of the analysis are believed to be useful for materials selection and actuator structure design of actuator in actuator fabrication. It is shown that the problem for bars of symmetrical structure is not divided into a plane problem and a bending problem. A way of simplifying the solution of the problem is found by an asymptotic method. After solving the problem for a laminated bar, formula that enable one to change from one-dimensional required quantities to three dimensional quantities are obtained. The derived analytical expression for ME coefficients depend on vibration frequency and other geometrical and physical parameters of laminated composites. Parametric studies are presented to evaluate the influences of material properties and geometries on strain distribution and the ME coefficient. Analytical expressions indicate that the vibration frequency strongly influences the strain distribution in the laminates, and that these effects strongly influence the ME coefficients. It is shown that for certain values of vibration frequency (resonance frequency), the ME coefficient becomes infinity; as a particular case, low frequency ME coefficient were derived as well.

STATIC AND DYNAMIC PERFORMANCE EVALUATION OF A PRE-STRESSED CONCRETE BRIDGE THROUGH FIELD TESTING AND MONITORING

2009 ◽  
Vol 09 (04) ◽  
pp. 711-728 ◽  
Author(s):  
C. S. CAI ◽  
M. ARAUJO ◽  
A. NAIR ◽  
X. SHI
Keyword(s):  
Quantitative Methods ◽  
Dynamic Performance ◽  
Three Dimensional ◽  
Field Tests ◽  
Field Measurements ◽  
Field Testing ◽  
Concrete Bridge ◽  
Bridge Structures ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

This paper presents field tests performed on a slab-on-girder pre-stressed concrete bridge. The bridge was tested under static loading, crawling loading, and dynamic loading. A full three-dimensional finite element prediction under both static and dynamic loadings was carried out and the results were compared with the field measurements. While acoustic emission (AE) monitoring of bridge structures is not a new vista, the method has not been fully exploited in bridge monitoring. Though numerous quantitative methods have been proposed, they have not yet developed to be useful for actual field tests of bridges. Therefore, in this study, an attempt was made to use the intensity analysis technique for damage quantification using the AE method.

scholarly journals Rheology of ice at the bed of Engabreen, Norway

2000 ◽  
Vol 46 (155) ◽  
pp. 611-621 ◽  
Author(s):  
Denis Cohen
Keyword(s):  
Three Dimensional ◽  
Field Measurements ◽  
Element Model ◽  
Basal Ice ◽  
Dimensional Finite Element ◽  
Ice Field ◽  
Frictional Forces ◽  
Two Parameters ◽  
Three Dimensional Finite Element ◽  
Sediment Layers

AbstractA three-dimensional finite-element model is used to analyze field data collected as dirty basal ice flowed past an instrumented obstacle at the bed of Engabreen, a temperate glacier in northern Norway The ice is modeled as an incompressible power-law fluid, with viscosity , where ΠD is the second invariant of the stretching tensor, and B and n are two parameters. Using measurements obtained in 1996 and 1997, two values of B are obtained, one using the measured normal stress difference across the obstacle, and the other using the measured bed-parallel force over the instrument. These two values are not equal, probably owing to small frictional forces at the bed unaccounted for in the numerical model. Hence, B ranges between 1.9 × 107 and 3.2 × 107 Pa s1/3 in 1996, and between 2.2 × 107 and 4.1 × 107 Pa s1/3 in 1997. These values are smaller than measured elsewhere for clean glacier or laboratory ice. Field measurements of water content, fabric and texture of the basal ice suggest that unbound water between thin sediment layers and lamellae of clean ice may act as a lubricant and significantly weaken the ice. Near-isotropic fabrics indicate that preferred fabric orientation does not enhance the deformation.

Receptivity to free-stream vorticity of flow past a flat plate with elliptic leading edge

2010 ◽  
Vol 653 ◽  
pp. 245-271 ◽  
Author(s):  
L.-U. SCHRADER ◽  
L. BRANDT ◽  
C. MAVRIPLIS ◽  
D. S. HENNINGSON
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Free Stream ◽  
Three Dimensional ◽  
Low Frequency ◽  
Leading Edge ◽  
Sound Waves ◽  
Streamwise Vorticity ◽  
Low Frequencies ◽  
Free Stream Turbulence

Receptivity of the two-dimensional boundary layer on a flat plate with elliptic leading edge is studied by numerical simulation. Vortical perturbations in the oncoming free stream are considered, impinging on two leading edges with different aspect ratio to identify the effect of bluntness. The relevance of the three vorticity components of natural free-stream turbulence is illuminated by considering axial, vertical and spanwise vorticity separately at different angular frequencies. The boundary layer is most receptive to zero-frequency axial vorticity, triggering a streaky pattern of alternating positive and negative streamwise disturbance velocity. This is in line with earlier numerical studies on non-modal growth of elongated structures in the Blasius boundary layer. We find that the effect of leading-edge bluntness is insignificant for axial free-stream vortices alone. On the other hand, vertical free-stream vorticity is also able to excite non-modal instability in particular at zero and low frequencies. This mechanism relies on the generation of streamwise vorticity through stretching and tilting of the vertical vortex columns at the leading edge and is significantly stronger when the leading edge is blunt. It can thus be concluded that the non-modal boundary-layer response to a free-stream turbulence field with three-dimensional vorticity is enhanced in the presence of a blunt leading edge. At high frequencies of the disturbances the boundary layer becomes receptive to spanwise free-stream vorticity, triggering Tollmien–Schlichting (T-S) modes and receptivity increases with leading-edge bluntness. The receptivity coefficients to free-stream vortices are found to be about 15% of those to sound waves reported in the literature. For the boundary layers and free-stream perturbations considered, the amplitude of the T-S waves remains small compared with the low-frequency streak amplitudes.

scholarly journals A Composite Perforated Partitioned Sandwich Panel With Corrugation for Underwater Low-Frequency Sound Absorption

2021 ◽  
Vol 7 ◽  
Author(s):  
Junyi Wang ◽  
Jiaming Hu ◽  
Yun Chen
Keyword(s):  
Acoustic Wave ◽  
Composite Structure ◽  
Sound Absorption ◽  
Low Frequency ◽  
Propagation Loss ◽  
Sound Waves ◽  
Acoustic Metamaterials ◽  
Underwater Sound ◽  
Underwater Acoustic ◽  
Frequency Sound

Underwater acoustic wave absorption and control play an important role in underwater applications. Various types of underwater acoustic metamaterials have been proposed in recent years with the vigorous development of acoustic metamaterials. Compared with airborne sound, underwater sound waves have a longer wavelength and much smaller propagation loss, making them more difficult to control. In addition, given that the acoustic impedance of water is much greater than that of air, numerous conventional materials and structures are not suited to underwater use. In this paper, we propose a composite structure based on an excellent broadband low-frequency sound absorber of air using aluminum mixed with rubber. Our composite structure possesses broadband low-frequency (<1,000 Hz) sound absorption underwater, omnidirectional high sound absorption coefficient under the oblique incidence (0–75°), and pressure resistance. It has promising applications for underwater acoustic wave control and contributes to the design of underwater acoustic metamaterials.

Mechanism of Cloud Droplet Motion under Sound Wave Actions

2020 ◽  
Vol 37 (9) ◽  
pp. 1539-1550 ◽  
Author(s):  
Fang-Fang Li ◽  
Ying-Hui Jia ◽  
Guang-Qian Wang ◽  
Jun Qiu
Keyword(s):  
Droplet Size ◽  
Sound Wave ◽  
Dominant Role ◽  
Sound Field ◽  
Cloud Droplet ◽  
Sound Frequency ◽  
Sound Waves ◽  
Cloud Droplets ◽  
Maximum Displacement ◽  
Precipitation Enhancement

AbstractSound waves have proven to be effective in promoting the interaction and aggregation of droplets. It is necessary to theoretically study the motion of particles in a sound field to develop new acoustic technology for precipitation enhancement. In this paper, the motion of cloud droplets due to a traveling sound wave field emitted from the ground to the air is simulated using the motion equation of point particles. The force condition of the particles in the oscillating flow field is analyzed. Meanwhile, the effects of droplet size, sound frequency, and sound pressure level (SPL) on the velocity and displacement of the droplets are also investigated. The results show that Stokes force and gravity play a dominant role in the falling process of cloud droplets, and the effect of the sound wave is mainly reflected in the fluctuation of velocity and displacement, which also promotes the displacement of cloud droplets to a certain extent. The maximum displacement increments of cloud droplets of 10 µm can reach 9200 µm due to the action of sound waves of 50 Hz and 143.4 dB. The SPL required for a noticeable velocity fluctuation for droplets of 10 µm with frequency of 50 Hz is 88.2 dB. When SPL < 100 dB and frequency > 500 Hz, the effect is negligible. The cloud droplet size plays a significant role in the motion, and the sound action is weaker for larger particles. For a smaller sound frequency and higher SPL, the effect of the sound wave is more prominent.

Analysis of Acoustic Performance of Compound Muffler by Finite Element Method

2012 ◽  
Vol 529 ◽  
pp. 257-263
Author(s):  
Deng Hui Cai ◽  
Xin Tan Ma
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Transmission Loss ◽  
Complex Structure ◽  
Three Dimensional ◽  
Sound Field ◽  
Acoustic Vibration ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Element Method

Since the theory of one-dimensional plane wave can not accurately predict the internal sound field of the complex structure muffler. The three-dimensional finite element method is adopted to establish the acoustic model of the composite muffler based on the application of composite muffler model. Transmission loss and characteristics of internal sound field of the composite muffler's are calculated through acoustic vibration software Sysnoise. The calculation shows that the muffler under the interference of fluid flow has the higher transmission loss compared with the absence of liquidity function with an additional silencer band. The analysis method and conclusions provide a basis for the design of composite muffler.

Simulation and Experimental Study of Ultrasonic Cleaning Based on Multi-Field Coupling

2013 ◽  
Vol 816-817 ◽  
pp. 1270-1273
Author(s):  
Qing Dong Hao ◽  
Fang Yi Li ◽  
Bao Long Gong
Keyword(s):  
Cross Sections ◽  
Staining Method ◽  
Three Dimensional ◽  
Sound Field ◽  
Field Measurements ◽  
Comsol Multiphysics ◽  
Ultrasonic Cleaning ◽  
Field Coupling ◽  
Cleaning Machine ◽  
Three Dimensional Models

In current Ultrasonic Cleaning simulation, high calculation complexity and low precision is a big problem. The disadvantages of reflecting the sound field characteristics inaccurately and quantitative difficulties exist in the sound field measurements. Firstly, the two-dimensional and three-dimensional models of Ultrasonic Cleaning are established in COMSOL Multiphysics and corresponding cleaning effects under different frequencies are simulated, then the frequencies of cleaning machine suitable for remanufactured components are determined. Finally, by means of staining method, sound field distribution on different work cross-sections in the Ultrasonic Cleaning process is studied. Halcon and Matlab are used in our investigation to deal with the experiment results in order to provide a new idea on the measurement of the sound field of Ultrasonic Cleaning.

3D Numerical Simulation of Electromagnetic Field during Low Frequency Electromagnetic Casting Process

2010 ◽  
Vol 154-155 ◽  
pp. 1472-1475
Author(s):  
Xiang Jie Wang ◽  
Jian Zhong Cui ◽  
Hai Tao Zhang
Keyword(s):  
Magnetic Field ◽  
Numerical Simulation ◽  
Three Dimensional ◽  
Low Frequency ◽  
Fem Analysis ◽  
Casting Process ◽  
Surface Region ◽  
Element Model ◽  
Current Intensity ◽  
Three Dimensional Finite Element

The rules of the distribution of magnetic field were carried out by numerical simulation. The distribution of magnetic field was got, and the effects of current intensity and frequency on the distribution of magnetic field were analyzed by constructing three-dimensional finite element model and using ANSYS software which is a kind of commercial FEM analysis software. The results show that the intensity of magnetic field is proportional to current intensity, magnetic field is mainly localized in the surface region of liquid melt and there is a notable edge effect in the corner.

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