scholarly journals Experimental studies of surface waves inside a cylindrical container

2011 ◽  
Vol 677 ◽  
pp. 39-62 ◽  
Author(s):  
CUNBIAO LEE ◽  
HUAIWU PENG ◽  
HUIJING YUAN ◽  
JIEZHI WU ◽  
MINGDE ZHOU ◽  
...  
Keyword(s):  
Surface Waves ◽  
High Frequency ◽  
Experimental Studies ◽  
Low Frequency ◽  
Capillary Waves ◽  
Physical Processes ◽  
Vortex Streets ◽  
Circular Capillary ◽  
Particle Imaging ◽  
Azimuthal Waves

We experimentally investigate the dynamics of surface waves excited by oscillations from a cylindrical sidewall. Particle-imaging-velocimetry measurements with fluorescent particles were used to determine the flow patterns near the sidewall of the cylindrical fluid container and to identify the locations of the evolving air–water interfaces. The high-frequency wall oscillations created four jets that originate at the cylindrical sidewall. Four vortex streets shed from the jets propagate from the sidewall to the centre of the container and subsequently excite a low-frequency gravity wave. The interaction between this gravitational surface wave and the high-frequency capillary waves was found to be responsible for creating droplet splash at the water surface. This phenomenon was first described as ‘Long-Xi’ or ‘dragon wash’ in ancient China. The physical processes for generating the droplet ejection, including the circular capillary waves, azimuthal waves, streaming jets and low-frequency gravity waves, are described in this paper.

Calculation-and-experimental estimation of the role of the frequency ratio in changing the endurance at two-frequency deformation modes

2019 ◽  
Vol 85 (1(I)) ◽  
pp. 64-71 ◽  
Author(s):  
M. M. Gadenin
Keyword(s):  
High Frequency ◽  
Experimental Studies ◽  
Low Frequency ◽  
Reduction Factor ◽  
Single Frequency ◽  
Cyclic Loads ◽  
Small Ratio ◽  
Harmonic Components ◽  
Deformation Modes

The cycle configuration at two-frequency loading regimes depends on the number of parameters including the absolute values of the frequencies and amplitudes of the low-frequency and high-frequency loads added during this mode, the ratio of their frequencies and amplitudes, as well as the phase shift between these harmonic components, the latter having a significant effect only with a small ratio of frequencies. Presence of such two-frequency regimes or service loading conditions for parts of machines and structures schematized by them can significantly reduce their endurance. Using the results of experimental studies of changes in the endurance of a two-frequency loading of specimens of cyclically stable, cyclically softened and cyclically hardened steels under rigid conditions we have shown that decrease in the endurance under the aforementioned conditions depends on the ratio of frequencies and amplitudes of operation low-frequency low-cycle and high-frequency vibration stresses, and, moreover, the higher the level of the ratios of amplitudes and frequencies of those stacked harmonic processes of loading the greater the effect. It is shown that estimation of such a decrease in the endurance compared to a single frequency loading equal in the total stress (strains) amplitudes can be carried out using an exponential expression coupling those endurances through a parameter (reduction factor) containing the ratio of frequencies and amplitudes of operation cyclic loads and characteristic of the material. The reduction is illustrated by a set of calculation-experimental curves on the corresponding diagrams for each of the considered types of materials and compared with the experimental data.

Fundamental properties of surface waves in lossless stratified structures

2010 ◽  
Vol 466 (2120) ◽  
pp. 2447-2469 ◽  
Author(s):  
Guido Valerio ◽  
David R. Jackson ◽  
Alessandro Galli
Keyword(s):  
Surface Waves ◽  
Dispersion Equation ◽  
High Frequency ◽  
Low Frequency ◽  
Layered Structures ◽  
Graphical Solution ◽  
Fundamental Properties ◽  
The Past ◽  
Permittivity And Permeability ◽  
Constitutive Parameters

This paper is focused on dispersive properties of lossless planar layered structures with media having positive constitutive parameters (permittivity and permeability), possibly uniaxially anisotropic. Some of these properties have been derived in the past with reference to specific simple layered structures, and are here established with more general proofs, valid for arbitrary layered structures with positive parameters. As a first step, a simple application of the Smith chart to the relevant dispersion equation is used to prove that evanescent (or plasmonic-type) waves cannot be supported by layers with positive parameters. The main part of the paper is then focused on a generalization of a common graphical solution of the dispersion equation, in order to derive some general properties about the behaviour of the wavenumbers of surface waves as a function of frequency. The wavenumbers normalized with respect to frequency are shown to be always increasing with frequency, and at high frequency they tend to the highest refractive index in the layers. Moreover, two surface waves with the same polarization cannot have the same wavenumber at a given frequency. The low-frequency behaviours are also briefly addressed. The results are derived by means of a suitable application of Foster’s theorem.

scholarly journals EXPERIMENTAL STUDIES OF THE DISTRIBUTION OF VARIOUS SPECIES OF SEISMOACOUSTIC WAVES IN THE COASTAL ZONE

2020 ◽  
Author(s):  
А.Н. Самченко ◽  
А.А. Пивоваров ◽  
А.Н. Швырев ◽  
И.О. Ярощук
Keyword(s):  
Surface Waves ◽  
Coastal Zone ◽  
Sea Of Japan ◽  
Peter The Great Bay ◽  
Experimental Studies ◽  
Low Frequency ◽  
Acoustic Signals ◽  
The Sea Of Japan ◽  
Preliminary Results ◽  
Peter The Great

В статье приводятся результаты экспериментальных исследований распространения низкочастотных акустических сигналов (33 Гц) на побережье залива Петра Великого Японского моря. Источник акустических сигналов опускался с борта маломерного судна в воду, а приемные системы были у береговой черты в воде и на суше. За счет использования трехкомпонентных виброметров стало возможно разделить принятые сигналы на различные типы волн (продольные, поперечные и поверхностные). Получены предварительные результаты расчета скоростных характеристик приходов различного типа волн на виброметры. The article presents the results of experimental studies on the propagation of low-frequency acoustic signals (33 Hz) on the coast of Peter the Great Bay of the Sea of Japan. The source of acoustic signals descended from the board of a small boat into the water, and the receiving systems were at the coastline in water and on land. Through the use of three component vibrometers, it has become possible to divide the received signals into various types of waves (longitudinal, transverse and surface waves). The preliminary results of calculating the speed characteristics of the arrival of various types of waves on vibrometers are obtained.

NONLINEAR INTERACTIONS BETWEEN TWO WIDELY SPACED MODES — EXTERNAL EXCITATION

1993 ◽  
Vol 03 (02) ◽  
pp. 417-427 ◽  
Author(s):  
S.A. NAYFEH ◽  
A.H. NAYFEH
Keyword(s):  
Natural Frequency ◽  
High Frequency ◽  
Analytical Study ◽  
Experimental Studies ◽  
Low Frequency ◽  
Harmonic Excitation ◽  
Frequency Mode ◽  
Large Contribution ◽  
High Frequency Mode ◽  
Two Degree Of Freedom

Recent experimental studies indicate that energy can be transferred from high- to low-frequency modes in structures with weak nonlinearity. In each of these experiments, a high-frequency mode was driven near its natural frequency but the response included a large contribution due to the first mode of the structure. In this paper, an analytical study of the response of a two-degree-of-freedom nonlinear system with widely spaced modes to a simple-harmonic excitation near the natural frequency of its high-frequency mode is presented. This system serves as a paradigm for the interaction of high- and low-frequency modes.

Nonlinear interaction of electrostatic surface waves in a semi-infinite plasma. Part 1. Derivation of the coupled mode equations

1981 ◽  
Vol 26 (2) ◽  
pp. 217-230 ◽  
Author(s):  
V. Atanassov ◽  
R. Mateev ◽  
I. Zhelyazkov
Keyword(s):  
Surface Waves ◽  
Nonlinear Interaction ◽  
High Frequency ◽  
Low Frequency ◽  
Density Perturbation ◽  
Coupled Mode ◽  
Hybrid Nature ◽  
Bulk Waves ◽  
Amplitude Attenuation

We have derived a set of coupled mode equations which govern the nonlinear interaction of three high-frequency electrostatic surface waves through a low-frequency density perturbation produced by them. The set is compared with that obtained when a similar problem is solved for bulk waves in an infinite plasma. Some differences are shown to exist caused by the specific features of surface waves such as the amplitude attenuation normal to the interface and their hybrid nature.

Nonlinear interaction of electrostatic surface waves in a semi-infinite plasma. Part 2. Time-dependent solutions to the coupled mode equations

1981 ◽  
Vol 26 (2) ◽  
pp. 231-252 ◽  
Author(s):  
V. Atanassov ◽  
E. Mateev ◽  
I. Zhelyazkov
Keyword(s):  
Surface Waves ◽  
Nonlinear Interaction ◽  
High Frequency ◽  
Low Frequency ◽  
Density Perturbation ◽  
Time Dependent ◽  
Opposite Case ◽  
Coupled Mode ◽  
Wave Resonance ◽  
Parametric Approximation

The coupled mode equations which govern the nonlinear interaction of three electrostatic high-frequency surface waves and a low-frequency density perturbation are analysed considering time-dependent solutions only. We show the existence of a filamentation instability in the static limit for the low-frequency density perturbation. In the opposite case (density perturbation close to the lowfrequency surface wave resonance) we arrive at a decay instability where only surface waves take part. The parametric approximation (growth rate and threshold) as well as the nonlinear evolution of both types of instabilities are studied.

RADIATION FROM A SOURCE NEAR A PLANE INTERFACE BETWEEN AN ISOTROPIC AND A GYROTROPIC DIELECTRIC

1964 ◽  
Vol 42 (11) ◽  
pp. 2153-2172 ◽  
Author(s):  
S. R. Seshadri ◽  
A. Hessel
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Field ◽  
Surface Waves ◽  
High Frequency ◽  
Free Space ◽  
Line Source ◽  
Low Frequency ◽  
Plane Interface ◽  
Magnetic Current ◽  
Asymptotic Evaluation

The radiation from a line source of magnetic current situated in free space near a plane interface between a semi-infinite free space and a semi-infinite gyrotropic dielectric is investigated for the case in which the gyrotropic axis is parallel to the line source. In addition to the space waves, it is found that in general two unidirectional surface waves are excited along the interface. The dispersion relations for the space and the surface waves are thoroughly examined. Both surface waves have different high-frequency cutoff but no low-frequency cutoff. The characteristics of these surface waves are investigated. An asymptotic evaluation of the total electromagnetic field is carried out for a particularly simple choice of the source frequency. For this frequency, the dependence of the efficiency of excitation of the surface waves on the distance of the source from the interface is determined. The radiation patterns are plotted for various values of the static magnetic field and the position of the source.

DETERMINATION OF THE INFLUENCE OF STRUCTURAL ELEMENTS ON ACOUSTIC EFFICIENCY AND BACK PRESSURE IN EXHAUST AND SUCTION NOISE SILENCERS

Akustika ◽  
2021 ◽  
pp. 210-216
Author(s):  
Nickolay Ivanov ◽  
Aleksandr Shashurin ◽  
Aleksandr Burakov
Keyword(s):  
Structural Design ◽  
High Frequency ◽  
Experimental Studies ◽  
Low Frequency ◽  
Back Pressure ◽  
Noise Generation ◽  
Structural Elements ◽  
The Relationship

The features of noise generation processes in exhaust and suction noise silencers are shown. A method for testing silencers has been developed. The classification of the main structural elements of exhaust and suction noise silencers, depending on the purpose, is proposed. Experimental studies of the relationship between the acoustic efficiency and the back pressure of silencers from the structural design of the elements are performed. The factors influencing the efficiency in the low-frequency and high-frequency regions of the spectrum are determined: the volume of silencers, the number of chambers, perforation, sound absorption, flow ejection, etc. Recommendations for the design of noise silencers are proposed.

Essential Role of Mid-latitude Air-Sea Interactions over the North Atlantic and North Pacific in the Occurrence of Euro-Atlantic Blocking

2021 ◽  
Author(s):  
Ho-Nam Cheung ◽  
Nour-Eddine Omrani
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
High Frequency ◽  
Low Frequency ◽  
Physical Processes ◽  
The North ◽  
Budget Analysis ◽  
The North Atlantic ◽  
The Impact ◽  
Sst Fronts

<p>Atmospheric blocking (“blocking”) is a crucial dynamic driver of extreme weather (e.g., severe/long-lasting cold spells, heat waves, drought and flood) over the extratropical region, where blocking occurs most frequently in boreal winter over the Euro-Atlantic and North Pacific sectors. In the state-of-the-art climate models, however, blocking frequency over the mid-latitude Euro-Atlantic sector is generally underestimated. Recent studies have pinpointed the importance of air-sea interactions over the North Atlantic in the formation of Euro-Atlantic blocking. In this study, we will demonstrate that the occurrence of Euro-Atlantic blocking is also related to the remote forcing from the North Pacific. Based on novel semi-idealized atmospheric general-circulation model experiments, we depict the impact of tropical and extratropical SST over different basins on the physical processes of Euro-Atlantic blocking events. We will show that the SST fronts over the mid-latitude North Atlantic and North Pacific jointly contribute to the occurrence of Euro-Atlantic blocking, whereas the contribution of tropical SST is relatively small. A budget analysis of the vorticity equation reveals that both high-frequency (< 8 days) and low-frequency (> 8 days) forcing contribute to the formation of Euro-Atlantic blocking events. The high-frequency forcing is associated with the intensification of an extratropical cyclone over the northwestern/central Atlantic, which is related to the North Atlantic storm tracks. The low-frequency forcing is associated with the eastward propagation of a Rossby wavetrain from North America to the Euro-Atlantic region. We will demonstrate how these physical processes are attributed to the North Atlantic and North Pacific SST fronts. Overall, our results provide new insights into the fundamental dynamics of Euro-Atlantic blocking events.</p>

Еxperimental Studies of Sliding Bearings of Locomotive Turbochargers by Their Level of Vibration

2018 ◽  
Vol 7 (4.3) ◽  
pp. 81
Author(s):  
Andrii Pogrebnyak ◽  
Andrii Yеvtushenko ◽  
Andrii Кravets ◽  
Artem Kovtunenko ◽  
Igor Tilichko
Keyword(s):  
High Frequency ◽  
Vibration Spectrum ◽  
Experimental Studies ◽  
Low Frequency ◽  
Vibration Velocity ◽  
Diesel Locomotive ◽  
Diagnostic Features ◽  
Sliding Bearings ◽  
Low Frequency Vibration ◽  
Free Bearing

The diagnostic features and sources of vibration of sliding bearings of diesel locomotive turbochargers (disappearance of the negative allowance on bearing bushings, self-oscillation in the bearing, self-oscillation when the negative allowance on the bearing bushing disappears, excitation of blade harmonics, etc.) are described in brief. The results of experimental studies of diesel locomotive turbochargers equipped with cylindrical and elliptical sliding bearings are shown. The specific spectra of vibration velocity of the bearing housings (cylindrical and elliptical) in the low-frequency range are presented. Bearing frequencies have been detected in the low-frequency vibration spectrum of the turbocharger housing with cylindrical bearings, and the connection of the detected diagnostic features with defects in sliding bearings has been established. Blade frequencies of the compressor and turbines on turbochargers with cylindrical and elliptical sliding bearings have been found in the high-frequency part of the vibration spectrum. These frequencies are necessary for identifying rotor harmonics and bearing frequencies. It has been established that for a defect-free bearing of turbochargers with elliptical and cylindrical sliding bearings, the vibration velocity of the rotor harmonics and the bearing frequency should not exceed the rated values.  

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