Measurement of the properties of fluids inside pipes using guided longitudinal waves

A new technique for measuring the longitudinal bulk velocity and shear viscosity of a fluid contained inside a pipe without a need for extracting a sample from inside of the pipe is presented. It is based on the measurement of the change of the dispersion properties and attenuation of longitudinal guided modes propagating in the pipe due to the presence of the fluid. The technique to extract longitudinal bulk velocity and shear viscosity is discussed and experimentally demonstrated by measuring both low-viscosity (distilled water and glycerol) and highly viscous fluids. The measured properties of glycerol agreed well with conventional methods and literature data for both the longitudinal bulk velocity (within 0.8%) and the viscosity (within 4%). For highly viscous fluid, the accuracy of the velocity measurement was found to be reduced slightly (within 1%), and the viscosity measurement became more accurate (within 1%).     

Attenuation of acoustic normal modes in piezoelectric plates loaded by viscous liquids

Attenuation cac versus viscosity eta of adjacent liquid is measured for each normal mode n generated in 30 different plates of commercially available, piezoelectric crystals with thickness-to-wavelength ratio in the range h/lamda = 0.6 - 2.5. Two modes with an optimal combination of sensitivity (0.1 dB/mm x cP), insertion loss (<35 dB), and stop-band rejection (>15 dB) are found in liquid-loaded 128 degrees Y,X + 90 degrees - LiNbO3 with h/lamda = 1.67. Both modes are suited for viscosity measurements and other sensing tasks in viscous liquids. They have predominantly longitudinal displacement and large propagation velocity v(n), about 15,000 m/s.     

In situ evaluation of density, viscosity, and thickness of adsorbed soft layers by combined surface acoustic wave and surface plasmon resonance

We show the theoretical and experimental combination of acoustic and optical methods for the in situ quantitative evaluation of the density, the viscosity, and the thickness of soft layers adsorbed on chemically tailored metal surfaces. For the highest sensitivity and an operation in liquids, a Love mode surface acoustic wave (SAW) sensor with a hydrophobized gold-coated sensing area is the acoustic method, while surface plasmon resonance (SPR) on the same gold surface as the optical method is monitored simultaneously in a single setup for the real-time and label-free measurement of the parameters of adsorbed soft layers, which means for layers with a predominant viscous behavior. A general mathematical modeling in equivalent viscoelastic transmission lines is presented to determine the correlation between experimental SAW signal shifts and the waveguide structure including the presence of the adsorbed layer and the supporting liquid from which it segregates. A methodology is presented to identify from SAW and SPR simulations the parameters representatives of the soft layer. During the absorption of a soft layer, thickness or viscosity changes are observed in the experimental ratio of the SAW signal attenuation to the SAW signal phase and are correlated with the theoretical model. As application example, the simulation method is applied to study the thermal behavior of physisorbed PNIPAAm, a polymer whose conformation is sensitive to temperature, under a cycling variation of temperature between 20 and 40 degrees C. Under the assumption of the bulk density and the bulk refractive index of PNIPAAm, thickness and viscosity of the film are obtained from simulations; the viscosity is correlated to the solvent content of the physisorbed layer.     

充粘性液体管材中超声导波的应力分析

对超声纵向导波在充粘液管材中的应力分布进行了分析,并讨论了用各模式检测充粘液管材的最佳频厚积范围和检测位置。分析表明,随频厚积的增加,L(0,1)和L(0,3)模式的平面内应力在管外壁上的值由负向变为正向,而L(0,2)和L(0,4)模式面内应力的值则相反,变换方向的点恰好在各模式的下一高阶模式群速度最大时的频厚积点附近;而在管内壁上,法向应力分布曲线达到零点的位置恰好在各模式群速度最大时的频厚积点附近。在各模式群速度较大的频厚积区域内,该模式在管内外表面上的平面内应力较大,而法向应力较小,因此能量泄漏较小。故在各模式群速度较大的频厚积区域内,用该模式来检测充粘液管材较合适。     

Viscosity measurement using drop coalescence in microgravity

We present in here validation studies of a new method for application in microgravity environment which measures the viscosity of highly viscous undercooled liquids using drop coalescence. The method has the advantage of avoiding heterogeneous nucleation at container walls caused by crystallization of undercooled liquids during processing. Homogeneous nucleation can also be avoided due to the rapidity of the measurement using this method. The technique relies on measurements from experiments conducted in near zero gravity environment as well as highly accurate analytical formulation for the coalescence process. The viscosity of the liquid is determined by allowing the computed free surface shape relaxation time to be adjusted in response to the measured free surface velocity for two coalescing drops. Results are presented from two sets of validation experiments for the method which were conducted on board aircraft flying parabolic trajectories. In these tests the viscosity of a highly viscous liquid, namely glycerin, was determined at different temperatures using the drop coalescence method described in here. The experiments measured the free surface velocity of two glycerin drops coalescing under the action of surface tension alone in low gravity environment using high speed photography. The liquid viscosity was determined by adjusting the computed free surface velocity values to the measured experimental data. The results of these experiments were found to agree reasonably well with the known viscosity for the test liquid used.     

Viscosity measurement of Newtonian liquids using the complex reflection coefficient

This work presents the implementation of the ultrasonic shear reflectance method for viscosity measurement of Newtonian liquids using wave mode conversion from longitudinal to shear waves and vice versa. The method is based on the measurement of the complex reflection coefficient (magnitude and phase) at a solid-liquid interface. The implemented measurement cell is composed of an ultrasonic transducer, a water buffer, an aluminum prism, a PMMA buffer rod, and a sample chamber. Viscosity measurements were made in the range from 1 to 3.5 MHz for olive oil and for automotive oils (SAE 40, 90, and 250) at 15 and 22.5degC, respectively. Moreover, olive oil and corn oil measurements were conducted in the range from 15 to 30degC at 3.5 and 2.25 MHz, respectively. The ultrasonic measurements, in the case of the less viscous liquids, agree with the results provided by a rotational viscometer, showing Newtonian behavior. In the case of the more viscous liquids, a significant difference was obtained, showing a clear non-Newtonian behavior that cannot be described by the Kelvin-Voigt model.     

管道损伤处纵向导波模态转换对损伤识别的影响

在管道导波检测中损伤反射回波包含了丰富的损伤相关信息,对回波信号的全面分析有助于识别损伤的几何特征。纵向模态导波与损伤相互作用会发生双模态转换,即L(0,2)导波与L(0,1)导波之间的相互转换。由L(0,2)导波转换而来的L(0,1)导波也反映了管道的损伤特征信息。利用数值模拟和实验方法,研究了损伤沿管道径向和周向扩展时L(0,1)和L(0,2)导波的反射特征。结果表明:L(0,2)导波与非贯穿型损伤相互作用会发生双模态转换现象,而与贯穿型损伤作用时,不发生双模态转换;对于周向长度一定的损伤,L(0,1)导波反射系数随损伤径向扩展呈先增大后减小的趋势,且损伤深度小于管道半壁厚时,L(0,1)导波与L(0,2)导波反射系数相当。研究结果为管道检测过程中评估损伤的径向深度提供了参考。     

Dynamics of oscillating viscous droplets immersed in viscous media

Summary Damped oscillations of a viscous droplet immersed in a viscous medium are considered in detail. The characteristic equation is solved numerically for arbitrary, finite fluid properties. The cylinder functions in the characteristic equation are solved using an accurate continued fraction algorithm, and the complex decay factor is searched using a minimization scheme. Oscillation frequency and damping rate results are presented for the fundamental mode, for various cases of practical interest (liquid-gas, and liquid-liquid systems), and the effect of the external medium properties are discussed. Results are compared to exact solutions for limiting cases, and to existing experimental data for both the fundamental and higher order modes. It is shown that the theoretical frequency prediction matches well with the experimental observation. Damping rate predictions, however, underestimate experimental observation in some cases, and this is thought to be due to surface impurities. The application of these results to the measurement of surface tension and viscosity of liquid droplets from single-droplet levitation experiments is also discussed.     

Axial power flow distributions of ultrasonic guided waves in viscous liquid-filled pipes

The axial power flow (APF) magnitude and attenuation distributions of ultrasonic longitudinal guided waves in viscous liquid-filled elastic pipes are investigated. The optimal location, optimal mode and its frequency-thickness product (fd) for the test of pipes filled with viscous liquid are chosen according to APF and attenuation distributions. The results show that the APF magnitude distribution is an important parameter in choosing the modes and parameters. A particular mode has weak dispersion in ranges of fd values with large group velocity, while other modes with smaller group velocity in the same fd ranges have stronger dispersion. It has been observed that, within these ranges, the chosen mode has a larger APF on the pipe's wall. Therefore, in the region of fd values where a particular mode has a large group velocity, this mode will be effective to be used in testing elastic pipes filled with viscous liquid. The results obtained from both the APF analysis and attenuation distribution are consistent.     

EFFECTS OF LIQUID VISCOSITY ON RHEOLOGY OF CONCENTRATED SUSPENSIONS

This paper presents the experimental results on the effects of liquid viscosity on the rheology of concentrated suspensions of solid particles in Newtonian liquids. Specifically, the relative viscosity of a pseudoplastic suspension decreases as the viscosity of the suspending liquid increases, indicating excess energy dissipation in a less viscous liquid. In contrast, the relative viscosity of a Newtonian suspension is only slightly affected by the liquid viscosity. It is in excellent agreement with the value predicted from the rigid sphere model which neglects nonhydrodynamic interactions, and assumes zero particle-to-liquid relative velocity. The flow behavior indices of both concentrated suspensions are independent of the liquid viscosity.     

识别薄板中兰姆波和体波的阶梯板方法

斜探头在某些频率下激励出的兰姆波,其群速度与体波的传播速度相近,所以通过判断传播速度不易区分出兰姆波和体波。通过数值模拟和实验,分别研究了激励频率为2 MHz的纵波和S0模态兰姆波在阶梯板上的反射特性,发现:在阶梯板上入射S0模态兰姆波时,有反射回波;而入射纵波时,无反射回波。基于这种反射特性的差别,提出了一种利用阶梯板区别薄板中兰姆波和体波的方法,该方法可用于确认探头的激励特性。     

Near-Infrared Refractometry of Liquids by Means of Waveguide ?erenkov Second-Harmonic Generation

A new, to our knowledge, method for measuring the refractive index of liquids in the near infrared by means of waveguide ?erenkov second-harmonic generation is presented. It makes use of a nonlinear planar waveguide whereby the liquid sample is put into place as the cover. By measurement of the output angle of the ?erenkov radiation mode (in the visible) the liquid sample refractive index (in the near infrared) is determined. Experiments were performed by means of a proton-exchanged LiNbO(3) waveguide as the sensor and a set of liquids with known refractive index. The values obtained are in good agreement with the expected ones, and the average accuracy is on the third decimal place.     

An alternative approach of acousto-ultrasonic technique formonitoring material anisotropy of fiber-reinforced composites

An alternative acousto-ultrasonic (AU) technique has been developed for nondestructive evaluation (NDE) of fiber-reinforced composites. The technique measures the time of flight (TOF) of AU waves, instead of the stress wave factor, by two low-frequency (0.5 MHz) transducers and relates TOF to material properties and fiber orientation. As the transducer separation increases, the measured time-domain AU signals clearly separate into two groups, since the excitation is under the first critical frequency, which correspond to the first two fundamental modes of the Lamb waves. One is an antisymmetric mode with slower propagation velocity and is highly dispersive, while the other is a symmetric mode with faster propagation velocity, which is very close to that of the longitudinal bulk wave, and is nearly nondispersive. The phase velocity in the composites can be accurately determined from the slopes of the TOF curves, and depends strongly on the azimuthal angle, frequency, and plate thickness. If the wave propagates away from the fiber direction, a slower but more attenuated wave is observed. Phase-velocity curves in azimuthal angles were obtained for E-glass/polyester, S-2-glass/epoxy, and Kevlar 49 composites. The theoretical solutions, for the longitudinal bulk wave and Lamb wave, are obtained by solving an eigenproblem once the material mechanical properties are defined. Good agreement is obtained between the measurements and the theoretical calculations     

EFFECTS OF LIQUID VISCOSITY ON RHEOLOGY OF CONCENTRATED SUSPENSIONS

ABSTRACT

This paper presents the experimental results on the effects of liquid viscosity on the rheology of concentrated suspensions of solid particles in Newtonian liquids. Specifically, the relative viscosity of a pseudoplastic suspension decreases as the viscosity of the suspending liquid increases, indicating excess energy dissipation in a less viscous liquid. In contrast, the relative viscosity of a Newtonian suspension is only slightly affected by the liquid viscosity. It is in excellent agreement with the value predicted from the rigid sphere model which neglects nonhydrodynamic interactions, and assumes zero particle-to-liquid relative velocity. The flow behavior indices of both concentrated suspensions are independent of the liquid viscosity.     

Propagation properties of longitudinal leaky surface waves on lithium tetraborate

Theoretical and experimental results of longitudinal leaky surface waves with a higher phase velocity than that of ordinary leaky surface waves and a low propagation loss on lithium tetraborate (LBO) are investigated in detail. They propagate along the surface with a phase velocity close to that of longitudinal bulk wave, slightly radiating two kinds of shear bulk waves (or one shear bulk wave in the case that one of two shear wave terms is uncoupled) into the solid. Most surface components of the mode consist of a longitudinal wave term and an electromagnetic wave term. The detailed propagation properties of the longitudinal leaky surface waves on LBO with the Euler angles (phi, theta, 90 degrees ) are investigated theoretically and experimentally. The (011) cut of LBO was found to be desirable for higher frequency SAW devices. One of the reasons why that mode on LBO has a low propagation loss is also discussed.     

The generation and detection of longitudinal guided waves in thin fibers using a conical transformer

This paper describes a technique to couple ultrasonic energy from a piezoceramic disc transducer into a fiber waveguide to induce longitudinal propagation. A polymer cone is utilized to bond the fiber waveguide onto the surface of the disc and to behave as a mechanical transformer, converting lateral displacements at its base into longitudinal displacements at its apex. Wideband finite element analysis (FEA) results are provided to show that the bond efficiently couples the radial modes of a disc transducer into fiber waveguides for longitudinal mode excitation. Furthermore, narrowband FEA is utilized to investigate how the geometry and material properties of the bond and waveguide influence the coupling efficiency. The technique is then quantified in terms of signal-to-coherent noise ratio (SCNR), reflecting its ability to generate the desired longitudinal waveguide mode and reject erroneous modes. Finally, design parameters are outlined for the successful implementation of this technique     

A microfluidic surface acoustic wave sensor platform: Application to high viscosity measurements

Acoustic Love wave oscillators offer a great potentiality to integrated viscosity measurements thanks to a high sensitivity and the lack of moving parts. The main limitation is insertion losses that increase with viscosity. To overcome this limitation, this paper reports the use of microfluidic techniques with a poly(dimethylsiloxane) (PDMS) chip bonded on the Love wave device. Liquid flows of aqueous glycerol solutions up to 0.939 Pa s (939cP, 98% glycerol) have been tested in oscillator mode. These results are promising for the viscoelastic study of viscous liquids. Modelisation using the classical perturbation theory is discussed.     

High velocity pseudosurface waves (HVPSAW)

Current interest in low-loss UHF filters for use in mobile and personal communication systems has led to a number of pseudo-SAW (PSAW) and SH mode based SAW devices. These filters can operate at higher frequencies than SAW-based ones for a given line-width because PSAW and SH mode velocities can be significantly higher than corresponding SAW velocities. Furthermore for certain orientations the attenuation of the PSAW is acceptably small. In this paper the existence of an independent high-velocity pseudo-SAW (HVPSAW) mode is discussed. The HVPSAW is shown to have a phase velocity close to the longitudinal bulk wave velocity and to be quasi-longitudinally polarized. The nature of this HVPSAW mode is described for both electrically open-circuited and layered metallic short-circuited conditions for several piezoelectric materials. Numerical and experimental data are presented which discuss the existence and properties of these high-velocity pseudosurface waves     

Analysis of piezoelectric bulk-acoustic-wave resonators as detectors in viscous conductive liquids

An analytical solution for the resonance condition of a piezoelectric quartz resonator with one surface in contact with a viscous conductive liquid is presented. The characteristic equation that describes the resonance condition and accounts for all interactions including acoustoelectric interactions with ions and dipoles in the solution is obtained in terms of the crystal and liquid parameters. A simple expression for the change in the resonance frequency is obtained. For viscous nonconductive solutions, the frequency change is reduced to a relationship in terms of the liquid density and viscosity. For dilute conductive liquid, the change in frequency is derived in terms of the solution conductivity and dielectric constant. The boundary conditions for the problem are defined with and without the electrical effects of electrodes. Experiments were conducted with various viscous and conductive chemical liquids using a fabricated miniature liquid flow cell containing an AT-cut quartz crystal resonator. The results, which show good agreement with the theory, on the use of quartz crystal resonators as conductivity and/or viscosity sensors are reported.