Simulation on Flow Field Induced by Vibration Surface of Low Frequency

2010 ◽  
Author(s):  
Ling Shen ◽  
Shuhong Liu ◽  
Yulin Wu
Keyword(s):  
Flow Field ◽  
Velocity Distribution ◽  
Numerical Computation ◽  
High Frequency ◽  
Ultrasonic Transducer ◽  
Sewage Treatment ◽  
Low Frequency ◽  
Vibration Source ◽  
Water Tank ◽  
Industrial Cleaning

Ultrasonic cavitation generated by high-frequency ultrasonic transducer is widely studied because this phenomenon could be applied in a great variety of fields, including medical therapy, industrial cleaning as well as sewage treatment. Flow field influenced by vibration source of low frequency, however, is less studied. For the present study, a water tank of 1000×600×500mm is investigated when a vibration surface that represents a transducer of less frequency vibrates in the vicinity of one wall. Numerical computation based on the method of dynamic mesh is applied. Furthermore, two different vibration patterns are simulated, i.e., piston movement and drumhead vibration. Results show different pressure and velocity distribution within water tank when vibration surface is working at various frequencies and amplitudes. Differences of the flow fields are found between these circumstances, and similarity is found with that induced by ultrasonic transducer. Analysis on differences is discussed for further study.

scholarly journals Piezoelectric Energy Harvesting with an Ultrasonic Vibration Source

Actuators ◽  
2019 ◽  
Vol 8 (1) ◽  
pp. 8
Author(s):  
Tao Li ◽  
Pooi Lee
Keyword(s):  
Energy Harvesting ◽  
High Power ◽  
High Frequency ◽  
Energy Harvester ◽  
Impedance Matching ◽  
Low Frequency ◽  
Vibration Source ◽  
Piezoelectric Energy ◽  
Power Ultrasonic ◽  
Ultrasonic Cutting

A piezoelectric energy harvester was developed in this paper. It is actuated by the vibration leakage from the nodal position of a high-power ultrasonic cutting transducer. The harvester was excited at a low displacement amplitude (0.73 µmpp). However, its operation frequency is quite high and reaches the ultrasonic range (24.4 kHz). Compared with another low frequency harvester (66 Hz), both theoretical and experimental results proved that the advantages of this high frequency harvester include (i) high current generation capability (up to 20 mApp compared to 1.3 mApp of the 66 Hz transducer) and (ii) low impedance matching resistance (500 Ω in contrast to 50 kΩ of the 66 Hz transducer). This energy harvester can be applied either in sensing, or vibration controlling, or simply energy harvesting in a high-power ultrasonic system.

Geometry Effects on the Flow Field and the Spectral Characteristics of a Triple Annular Swirler

2003 ◽  
Author(s):  
Guoqiang Li ◽  
Ephraim J. Gutmark
Keyword(s):  
Flow Field ◽  
Boundary Conditions ◽  
High Frequency ◽  
Vortex Breakdown ◽  
Swirling Flow ◽  
Low Frequency ◽  
Tube Length ◽  
Formation Mechanisms ◽  
Recirculation Bubble ◽  
Inlet Conditions

The dynamics of vortex breakdown are important to the performance of gas turbine combustors where swirling flows are extensively used to stabilize the flame and extend the lean flammability limit (LBO). Due to the strong interaction of vortical structures in the swirling flow with heat release and acoustical modes, vortex breakdown mechanism is essential to understanding the thermoacoustic behavior and to the development of combustion instability control strategy. This paper analyzes the vortex breakdown behavior downstream of a Triple Annular Research Swirler (TARS) based on velocity flow field data from stereoscopic PIV measurement and spectral data from hotwire/film measurements. The vortical structure is highly dependent on the different swirler combinations (swirler geometry) as well as on inlet conditions such as air flow-rate, mixing tube length and downstream conditions such as exhaust nozzle contraction ratio. The scale, location, strength, and formation mechanisms of the large-scale vortices vary for different geometries. The shape of the recirculation bubble changes with the outlet boundary conditions, suggesting that the swirling flow inside the combustion chamber remains subcritical downstream of the vortex breakdown. However, spectral analysis reveals that the dominant frequencies close to the exit of the TARS show only slight change for different outlet boundary conditions. Three ranges of frequencies characterize the spectral domain of TARS: high frequency close to the TARS exit, middle range frequency downstream of this region, and low frequency in most regions further downstream. The sources of instabilities in these three regions could be attributed to the strong shear layer, precessing vortex core and interaction between spanwise and azimuthal instabilities. The outlet boundary conditions affect the middle and low frequency range but have no effect on the high frequency. The inlet conditions have global effect on the entire flow region.

scholarly journals Exact and limiting solutions of fluid flow for axially oscillating cylindrical pipe and annulus

2021 ◽  
Vol 3 (3) ◽  
Author(s):  
U. K. Sarkar ◽  
Nirmalendu Biswas
Keyword(s):  
Velocity Distribution ◽  
High Frequency ◽  
Oscillatory Flow ◽  
Stokes Equations ◽  
Low Frequency ◽  
Navier Stokes ◽  
Cylindrical Pipe ◽  
Navier Stokes Equations ◽  
Cylindrical Annulus

AbstractThe Navier–Stokes equations have been solved to derive the expressions of the velocity distributions for two cases: (1) oscillatory flows inside and outside of an axially oscillating cylindrical pipe, and (2) oscillatory flow inside an axially oscillating cylindrical annulus. In both the cases, in addition to the exact expressions for the velocity profiles, particular emphasis has been given for the determination of approximate velocity distributions for the high frequency and low frequency or quasi-static limits. It is shown that, for sufficiently large value of an appropriate frequency parameter, the velocity distribution inside the axially or longitudinally oscillating cylindrical annulus can be approximated as a superposition of the velocity distribution inside an axially oscillating cylindrical pipe of radius $${\bar R_o}$$ R ¯ o and the velocity distribution outside an axially oscillating cylindrical pipe of radius $${\bar R_i}$$ R ¯ i , where $${\bar R_i}$$ R ¯ i and $${\bar R_o}$$ R ¯ o are the inner and outer radii of the axially oscillating annulus, respectively.

Oscillatory and streaming flow between two spheres due to combined oscillations

2017 ◽  
Vol 826 ◽  
pp. 335-362
Author(s):  
Dejuan Kong ◽  
Anita Penkova ◽  
Satwindar Singh Sadhal
Keyword(s):  
Flow Field ◽  
Phase Difference ◽  
High Frequency ◽  
Amplitude Ratio ◽  
Dominant Role ◽  
Outer Region ◽  
Low Frequency ◽  
Frequency Oscillation ◽  
Steady Streaming ◽  
Streaming Flow

The flow induced by the combined torsional and transverse oscillations of a sphere with amplitude ratio $\unicode[STIX]{x1D6FC}$ and phase difference $\unicode[STIX]{x1D6FD}$ in a concentric spherical container is examined. Analytical solutions of the leading-order flow field and shear stress profiles have been obtained. Steady streaming flows are also analysed not only for the case of unrestricted Womersley number $|M|$, but also in the low-frequency $(|M|\ll 1)$ and high-frequency ($|M|\gg 1$) limits. At high frequency, the flow field has been divided into three regions: two boundary layers and the outer region. The streaming flow field is determined for the limiting case of the streaming Reynolds number $R_{s}\ll 1$. The results are compared with those of single torsional or transverse oscillation, and found to match very well. The amplitude ratio $\unicode[STIX]{x1D6FC}$ and phase difference $\unicode[STIX]{x1D6FD}$, in determining the streaming, are also discussed. The number and direction of steady streaming recirculation on the $r$–$\unicode[STIX]{x1D703}$ plane depend on value of the amplitude ratio $\unicode[STIX]{x1D6FC}$. The phase difference $\unicode[STIX]{x1D6FD}$ plays a dominant role in the azimuthal velocity $u_{1\unicode[STIX]{x1D719}}^{(s)}$ of steady streaming. When $\unicode[STIX]{x1D6FD}$ is approximately $(2n+1)\unicode[STIX]{x03C0}/2$, $u_{1\unicode[STIX]{x1D719}}^{(s)}$ vanishes under low-frequency oscillation, while steady streaming has a recirculation on the $r$–$\unicode[STIX]{x1D719}$ plane under higher-frequency oscillation.

Producing Mechanism on Flow Regeneration Noise from Muffler Element with Inserted Tube

2012 ◽  
Vol 538-541 ◽  
pp. 1977-1980
Author(s):  
Hai Jun Zhao ◽  
Jia Dong Chang ◽  
Hai Xia Wang ◽  
Qi Li
Keyword(s):  
Kinetic Energy ◽  
Flow Field ◽  
Flow Velocity ◽  
Numerical Computation ◽  
Frequency Characteristic ◽  
Low Frequency ◽  
Turbulence Kinetic Energy ◽  
Sound Power ◽  
Structure Parameters ◽  
Constant Distribution

Structure parameters of muffler element with inserted tube are firstly determined, it is analyzed to the inserted length effecting on sound power of flow regeneration noise and frequency characteristic, and distribution feature of flow velocity and turbulence kinetic energy is explored by numerical computation of flow field. It is shown that flow regeneration noise of muffler element with inserted tube forms according to confined incomplete flow-inject, it presents wide frequency band, and its energy focus on middle and low frequency, especially it is about 600Hz, Strouhal Number is 0.5. When its structure parameters is constant, distribution feature of flow velocity and turbulence kinetic energy doesn’t change with flow velocity, and difference is numerical dimension, and turbulence kinetic energy distributes near inserted tube in wall, this is area occurring flow regeneration noise, so producing mechanism of flow regeneration noise from muffler element with inserted tube is achieved.

Simulations of high-resolution images of amorphous silicon films

1986 ◽  
Vol 44 ◽  
pp. 544-545
Author(s):  
G. Y. Fan ◽  
J. M. Cowley
Keyword(s):  
Electron Microscope ◽  
High Frequency ◽  
Fourier Transformation ◽  
Amorphous Materials ◽  
Low Frequency ◽  
Chromatic Aberration ◽  
Structure Information ◽  
Frequency Components ◽  
High Resolution Images ◽  
Spatial Frequency Spectrum

It is well known that the structure information on the specimen is not always faithfully transferred through the electron microscope. Firstly, the spatial frequency spectrum is modulated by the transfer function (TF) at the focal plane. Secondly, the spectrum suffers high frequency cut-off by the aperture (or effectively damping terms such as chromatic aberration). While these do not have essential effect on imaging crystal periodicity as long as the low order Bragg spots are inside the aperture, although the contrast may be reversed, they may change the appearance of images of amorphous materials completely. Because the spectrum of amorphous materials is continuous, modulation of it emphasizes some components while weakening others. Especially the cut-off of high frequency components, which contribute to amorphous image just as strongly as low frequency components can have a fundamental effect. This can be illustrated through computer simulation. Imaging of a whitenoise object with an electron microscope without TF limitation gives Fig. 1a, which is obtained by Fourier transformation of a constant amplitude combined with random phases generated by computer.

SEM image sharpness analysis

1996 ◽  
Vol 54 ◽  
pp. 142-143
Author(s):  
M. T. Postek ◽  
A. E. Vladar
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Quantitative Information ◽  
Primary Electron ◽  
Image Sharpness ◽  
Critical Dimensions ◽  
Sem Image ◽  
Frequency Changes ◽  
Electron Microscopes ◽  
Scanning Electron

Fully automated or semi-automated scanning electron microscopes (SEM) are now commonly used in semiconductor production and other forms of manufacturing. The industry requires that an automated instrument must be routinely capable of 5 nm resolution (or better) at 1.0 kV accelerating voltage for the measurement of nominal 0.25-0.35 micrometer semiconductor critical dimensions. Testing and proving that the instrument is performing at this level on a day-by-day basis is an industry need and concern which has been the object of a study at NIST and the fundamentals and results are discussed in this paper.In scanning electron microscopy, two of the most important instrument parameters are the size and shape of the primary electron beam and any image taken in a scanning electron microscope is the result of the sample and electron probe interaction. The low frequency changes in the video signal, collected from the sample, contains information about the larger features and the high frequency changes carry information of finer details. The sharper the image, the larger the number of high frequency components making up that image. Fast Fourier Transform (FFT) analysis of an SEM image can be employed to provide qualitiative and ultimately quantitative information regarding the SEM image quality.

Real Ear Sound Pressure Levels Developed by Three Portable Stereo System Earphones

1992 ◽  
Vol 1 (4) ◽  
pp. 52-55 ◽  
Author(s):  
Gail L. MacLean ◽  
Andrew Stuart ◽  
Robert Stenstrom
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Low Frequency ◽  
Test System ◽  
Output Frequency ◽  
Frequency Effects ◽  
Adult Men ◽  
Frequency Responses ◽  
Significant Difference ◽  
Sound Pressure Levels

Differences in real ear sound pressure levels (SPLs) with three portable stereo system (PSS) earphones (supraaural [Sony Model MDR-44], semiaural [Sony Model MDR-A15L], and insert [Sony Model MDR-E225]) were investigated. Twelve adult men served as subjects. Frequency response, high frequency average (HFA) output, peak output, peak output frequency, and overall RMS output for each PSS earphone were obtained with a probe tube microphone system (Fonix 6500 Hearing Aid Test System). Results indicated a significant difference in mean RMS outputs with nonsignificant differences in mean HFA outputs, peak outputs, and peak output frequencies among PSS earphones. Differences in mean overall RMS outputs were attributed to differences in low-frequency effects that were observed among the frequency responses of the three PSS earphones. It is suggested that one cannot assume equivalent real ear SPLs, with equivalent inputs, among different styles of PSS earphones.

Evaluation of Special Hearing Aids for Deaf Children

1971 ◽  
Vol 36 (4) ◽  
pp. 527-537 ◽  
Author(s):  
Norman P. Erber
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Hearing Aid ◽  
Low Frequency ◽  
Acoustic Stimulation ◽  
Deaf Children ◽  
Frequency Range ◽  
Frequency Limit ◽  
Unpublished Studies ◽  
Published Research

Two types of special hearing aid have been developed recently to improve the reception of speech by profoundly deaf children. In a different way, each special system provides greater low-frequency acoustic stimulation to deaf ears than does a conventional hearing aid. One of the devices extends the low-frequency limit of amplification; the other shifts high-frequency energy to a lower frequency range. In general, previous evaluations of these special hearing aids have obtained inconsistent or inconclusive results. This paper reviews most of the published research on the use of special hearing aids by deaf children, summarizes several unpublished studies, and suggests a set of guidelines for future evaluations of special and conventional amplification systems.

Efeitos do Método Pilates sobre a variabilidade da frequência cardíaca, flexibilidade e variáveis antropométricas em indivíduos sedentários

2016 ◽  
Vol 17 (1) ◽  
pp. 66
Author(s):  
Maria Lina Silva Leite
Keyword(s):  
High Frequency ◽  
Low Frequency

O objetivo deste estudo foi avaliar os efeitos do Método Pilates sobre a variabilidade da frequência cardíaca, na flexibilidade e nas variáveis antropométricas em indivíduos sedentários. O presente estudo contou com 14 voluntárias do sexo feminino, na faixa etária entre 40 e 55 anos, que realizaram 20 sessões de exercícios do Método Pilates, duas vezes por semana, com duração de 45 minutos cada sessão, dividida em três fases: repouso, exercício e recuperação. As variáveis estudadas foram: os dados antropométricos, flexibilidade avaliada utilizando o teste de sentar-e-alcançar com o Banco de Wells, e intervalos R-R usando um cardiotacômetro. O processamento dos sinais da frequência cardíaca foi efetuado em ambiente MatLab 6.1®, utilizando a TWC. Os dados coletados foram submetidos ao teste de normalidade de Shapiro Wilk e foi utilizado o teste de Wilcoxon e Anova One Way (α = 0,05). Nos resultados, observou-se que não houve diferenças significativas entre os valores antropométricos e de frequência cardíaca, porém houve aumento da flexibilidade com o treinamento. Comparando a primeira e a vigésima sessão com relação aos parâmetros low frequency (LF), high frequency (HF), e relação LF/HF, não houve diferença na fase de repouso e foram constatadas diferenças significativas de LF (p = 0,04) e HF (p = 0,04) na fase de exercício e diferença significativa de LF/HF (p = 0,05) na fase de recuperação. Comparando os parâmetros nos períodos de repouso, exercícios e recuperação durante a primeira sessão e durante a vigésima sessão, não houve diferença significativa nos parâmetros LF, HF e LF/HF. Pode-se concluir que, em relação à flexibilidade, foi observada uma melhora significativa, enquanto a análise da frequência cardíaca caracterizou a intensidade do exercício de 50% da capacidade funcional das voluntárias. Em relação aos parâmetros LF, HF e LF/HF foram observados um aumento da variabilidade da frequência cardíaca, provavelmente produto da atividade do Método Pilates. A Transformada Wavelet (TWC) mostrou-se um Método adequado para as análises da variabilidade da frequência cardíaca.Palavras-chave: frequência cardíaca, Transformada Wavelet, Pilates.

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