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1.
For the characterization of the unknown material properties of a layered cylindrical structure, axially symmetric wave signals transmitted and reflected by the structure have been used. Since only a single wave mode propagates in the structure, the measurement and analysis of the transmitted and reflected signals can be simplified significantly. The evaluation of the material properties of the layers can be achieved with great accuracy. In this paper, we first derive the transmission and reflection coefficients for the layered cylindrical structure sonified axisymmetrically by an incident cylindrical wave. We then relate the spectra of the transmitted and reflected wave signals to the transmission and reflection coefficients as ratio functions. The time-domain signals transmitted and reflected by the structure can then be reconstructed from a routine application of the Fourier integrals. A three-layered aluminum/epoxy/aluminum tube is used to illustrate the application of the expressions for both the forward and inverse problems. The results show that the technique developed in this study can be used very effectively for the characterization of layered cylindrical structures. 相似文献
2.
High Temperature - The counter interaction of detonation waves in a liquid with bubbles of a combustible gas is considered based on numerical simulation. The effect of the initial volumetric gas... 相似文献
3.
V. G. Peschansky D. I. Stepanenko 《Journal of Superconductivity and Novel Magnetism》2007,20(2):145-148
The propagation of spin waves in Q2D layered conductors placed in a magnetic field, is studied. It is shown, that at certain
orientations of the magnetic field with respect to the layers the collisionless absorption is absent and weakly damping spin
waves can propagate even under the strong spatial dispersion. 相似文献
4.
A. A. Levchenko M. Yu. Brazhnikov G. V. Kolmakov L. P. Mezhov-Deglin 《Journal of Low Temperature Physics》2002,126(1-2):569-577
We present the results of experimental investigations of weak turbulence in the system of capillary waves on the charged surface of liquid hydrogen. The formation of the Kolmogorov cascade was observed in the frequency interval from 100Hz to 10 kHz. It was found that the correlation function of the surface deviation from the equilibrium flat state can be described by a power function with index m=–3.7±0.3 for the case of exciting the surface by harmonic force at one frequency and with m=–3±0.3 for the case of excitation at two frequencies. The results are in qualitative agreement with theoretical predictions. 相似文献
5.
Sergey Alekseenko Andrey Cherdantsev Mikhail Cherdantsev Dmitry Markovich 《Microgravity science and technology》2009,21(Z1):221-226
Annular gas–liquid flow was investigated using high-speed modification of LIF technique. The evolution of liquid film surface
was studied with high spatial and temporal resolution. It was found that all waves may be classified into primary and secondary
waves; all the secondary waves arise due to instability of the back fronts of primary waves. The areas of inception and velocity
of secondary waves were compared for annular flow with and without entrainment. The similarities and differences of wavy structure
in both cases were demonstrated. 相似文献
6.
The fluid flow in a non-uniformly rotating (librating) cylinder about a horizontal axis is experimentally studied. In the absence of librations the fluid performs a solid-body rotation together with the cavity. Librations lead to the appearance of steady zonal flow in the whole cylinder and the intensive steady toroidal flows near the cavity corners. If the frequency of librations is twice lower than the mean rotation rate the inertial waves are excited. The oscillating motion associated with the propagation of inertial wave in the fluid bulk leads to the appearance of an additional steady flow in the Stokes boundary layers on the cavity side wall. In this case the heavy particles of the visualizer are assembled on the side wall into ring structures. The patterns are determined by the structure of steady flow, which in turn depends on the number of reflections of inertial wave beams from the cavity side wall. For some frequencies, inertial waves experience spatial resonance, resulting in inertial modes, which are eigenmodes of the cavity geometry. The resonance of the inertial modes modifies the steady flow structure close to the boundary layer that is manifested in the direct rebuilding of patterns. It is shown that the intensity of zonal flow, as well as the intensity of steady flows excited by inertial waves, is proportional to the square of the amplitude of librations. 相似文献
7.
A continuation method is applied to investigate the linear stability of the steady, axisymmetric thermocapillary flows in
liquid bridges. The method is based upon an appropriate extended system of perturbation equations depending on the nature
of transition of the basic flow. The dependence of the critical Reynolds number and corresponding azimuthal wavenumber on
serval parameters is presented for both cylindrical and non-cylindrical liquid bridges. 相似文献
8.
本文根据电磁感应原理结合热动力学烟囱效应,分析了感应加热式锌锅锌液形成稳定流动原因,推导出锌锅两个感应加热器回路接线要使它们的磁场方向要相同的结论。
锌锅感应加热器停电是严重的故障,会造成熔沟内锌液凝固。一旦熔沟内锌液发生凝固,必须采用长时间低功率来使熔沟内“锌锭”缓慢熔化,以释放锌锭受热产生的应力避免造成耐材损坏引起漏锌。初步探讨了一种采用集肤效应原理来快速解决熔沟内凝固“锌锭”的方法。 相似文献
9.
Leonid Victorovich Abdurakhimov Maxim Yurievich Brazhnikov Alexander Alexeevich Levchenko 《Journal of Low Temperature Physics》2008,150(3-4):431-434
Excitation of the surface of liquid hydrogen by a harmonic force at low frequencies leads to the formation of turbulent cascade
in the system of capillary waves. We have found that the probability density function for a high-frequency surface deviation
from equilibrium state in the regime of developed turbulence is well approximated by the Gaussian distribution.
相似文献
10.
The elastodynamic behavior of waves in a thermo-microstretch elastic homogeneous isotropic plate bordered with layers of inviscid
liquid on both sides subjected to stress-free thermally insulated and isothermal conditions is investigated in the context
of Lord and Shulman and Green and Lindsay theories of thermoelasticity. The mathematical model has been simplified by using
the Helmholtz decomposition technique, and the frequency equations for different mechanical situations are obtained and discussed.
The special cases such as short wavelength waves and regions of the secular equations are also discussed. Finally, the numerical
solution is carried out for a magnesium crystal composite material plate bordered with water. The dispersion curves, attenuation
coefficients, amplitudes of dilatation, microrotation, microstretch, and temperature distribution for the symmetric and skew-symmetric
wave modes are presented graphically. 相似文献
11.
12.
S. V. Alekseenko V. A. Antipin A. V. Cherdantsev S. M. Kharlamov D. M. Markovich 《Microgravity science and technology》2008,20(3-4):271-275
High-speed fluorescent visualization complex has been developed for quantitative investigation of the process of interaction of waves on liquid film in annular two-phase flow. Evolution of ripples on disturbance waves surface and disturbance waves coalescence are investigated. It is shown that all the ripples in presence of disturbance waves appear at the base of the back front of disturbance waves and then either decelerate, travel on substrate and are overtaken by the following disturbance wave or accelerate, grow and then disappear at the front of disturbance wave. The disappearance happens due to entrainment of liquid into the core of gas stream. Several scenarios of coalescence of disturbance waves were identified. For disturbance waves with close velocities different types of remote interaction were observed. 相似文献
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14.
Taishi Yano Koichi Nishino Satoshi Matsumoto Ichiro Ueno Atsuki Komiya Yasuhiro Kamotani Nobuyuki Imaishi 《Microgravity science and technology》2018,30(5):599-610
This paper reports an overview and some important results of microgravity experiments called Dynamic Surf, which have been conducted on board the International Space Station from 2013 to 2016. The present project mainly focuses on the relations between the Marangoni instability in a high-Prandtl-number (Pr=?67 and 112) liquid bridge and the dynamic free surface deformation (DSD) as well as the interfacial heat transfer. The dynamic free surface deformations of large-scale liquid bridges (say, for diameters greater than 10 mm) are measured with good accuracy by an optical imaging technique. It is found that there are two causes of the dynamic free surface deformation in the present study: the first is the time-dependent flow behavior inside the liquid bridge due to the Marangoni instability, and the second is the external disturbance due to the residual acceleration of gravity, i.e., g-jitter. The axial distributions of DSD along the free surface are measured for several conditions. The critical parameters for the onset of oscillatory Marangoni convection are also measured for various aspect ratios (i.e., relative height to the diameter) of the liquid bridge and various thermal boundary conditions. The characteristics of DSD and the onset conditions of instability are discussed in this paper. 相似文献
15.
I. N. Aliev A. R. Mil'divskii I. A. Naumov 《Journal of Engineering Physics and Thermophysics》2002,75(5):1113-1115
It is shown that if a thin liquid layer is brought into the state of steady motion, the surface tension decreases efficiently for waves propagating along the flow or in opposition to it and the conditions of occurrence of the instability of a charged liquid surface are made substantially easier. 相似文献
16.
Lev A. Slobozhanin Valentina M. Shevtsova J. Iwan D. Alexander José Meseguer José M. Montanero 《Microgravity science and technology》2012,24(2):65-77
This paper reviews the dynamics of breaking or oscillating axisymmetric liquid bridges, and estimates of the energy which
is needed to break a liquid bridge. We consider a liquid bridge spanning two coaxial equal disks with sharp edges and held
by surface-tension forces. The liquid volume is assumed to be conserved under perturbations, and the contact lines are pinned
to the disk edges. The perturbations are finite and axisymmetric. An analysis is based on the one-dimensional models previously
used in capillary jet theory and last several decades for study a liquid bridge dynamics. According to the scientific project
JEREMI (Japanese and European Research Experiment on Marangoni Instabilities), the first stage of the space experiment on
ISS will involve an isothermal liquid bridge with a gas blowing parallel to the axial direction of the bridge. The geometry
corresponds to a cylindrical volume liquid bridge coaxially placed into an outer cylinder with solid walls. The gas enters
the annular duct bounded by the outer cylinder and the internal system consisting of supporting vertical rods and the liquid
bridge. Considering that the bridge is small (the rod’s radii are 3 mm) and the gas velocity is typically (0.25 ÷ 0.37) m/s,
the perturbations cannot be considered small. Thus, one may assume that the amplitude of the liquid bridge perturbations is
sufficiently large that departures from linearity must be considered. 相似文献
17.
G. V. Kolmakov A. A. Levchenko M. Yu. Brazhnikov L. P. Mezhov-Deglin A. N. Silchenko P. V. E. McClintock 《Journal of Low Temperature Physics》2005,138(3-4):519-524
No Heading We study the free decay of capillary turbulence on the charged surface of liquid hydrogen. We find that the decay begins from the high frequency spectral domains of the surface oscillations and is of a quasi-adiabatic character. The characteristic relaxation time of the whole turbulent cascade is close to the viscous damping time for capillary waves of frequency equal to the driving frequency.PACS numbers: 47.27.–i, 47.25.+i 相似文献
18.
为解决制冷剂除霜系统融霜结束后可能发生的压缩机湿压缩和库温波动问题,本文在库温-20℃、结霜量3 kg工况下,以风机延时开启的时间为变量,对除霜结束后风机延时开启0~180 s进行单一变量的实验研究。从除霜结束后的库温波动、除霜时间、系统恢复制冷后压缩机吸气状态方面,比较分析风机延时不同时间开启对系统运行特性的影响。结果表明:除霜结束不延时开启风机,库温将突升5℃,并且恢复制冷的前4 min,压缩机存在湿压缩问题;除霜结束风机延时开启的最佳时间为140~180 s,此时库温升高比风机不延时开启情况降低3℃,总库温波动在5℃以内,除霜时间在12 min左右,且除霜结束恢复制冷时有效避免了压缩机可能出现的湿压缩问题。 相似文献
19.
横向风作用下公铁两用双层桥的上、下桥面间存在相互的气动干扰,为研究公铁两用组合桥间隔高度对列车走行性的影响,针对某分离式公铁两用混凝土箱梁桥,采用计算流体动力学(CFD)数值模拟和风-车-桥耦合振动研究的方法,分析了上、下桥面间隔高度对列车气动特性和车辆动力响应的影响。分析结果表明,公铁两用组合桥间隔高度对列车的气动特性和动力响应影响显著,间隔高度减小,列车升力系数和竖向加速度显著增大,轮重减载率也随之增大。公铁两用组合桥的设计应考虑间隔高度对列车的影响,以选择合理的间隔高度。 相似文献
20.
Shi‐Yang Tang Bugra Ayan Nitesh Nama Yusheng Bian James P. Lata Xiasheng Guo Tony Jun Huang 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(28):3861-3869
Micro‐ to nanosized droplets of liquid metals, such as eutectic gallium indium (EGaIn) and Galinstan, have been used for developing a variety of applications in flexible electronics, sensors, catalysts, and drug delivery systems. Currently used methods for producing micro‐ to nanosized droplets of such liquid metals possess one or several drawbacks, including the lack in ability to control the size of the produced droplets, mass produce droplets, produce smaller droplet sizes, and miniaturize the system. Here, a novel method is introduced using acoustic wave‐induced forces for on‐chip production of EGaIn liquid‐metal microdroplets with controllable size. The size distribution of liquid metal microdroplets is tuned by controlling the interfacial tension of the metal using either electrochemistry or electrocapillarity in the acoustic field. The developed platform is then used for heavy metal ion detection utilizing the produced liquid metal microdroplets as the working electrode. It is also demonstrated that a significant enhancement of the sensing performance is achieved by introducing acoustic streaming during the electrochemical experiments. The demonstrated technique can be used for developing liquid‐metal‐based systems for a wide range of applications. 相似文献