Ultrasonic Waves In Water Research Articles

3D printed triboelectric nanogenerator for underwater ultrasonic sensing

The underwater ultrasound power measurement has become necessary due to the rapid development of sonochemistry and sonocatalysis. This article presents construction of novel triboelectric nanogenerator (TENG) and its application for a detection of ultrasonic waves in water. The device was 3D printed using widely available and cost-effective materials. TENG consisted of the device housing and movable polymer pellets confined between flat electrodes. The device housing and pellets were 3D printed via stereolithography (SLA) and fused deposition modelling (FDM) methods, respectively. The pellets moved periodically driven by the ultrasonic waves leading to generation of an alternating voltage signal. The electric response of TENG was calibrated using a commercially available ultrasonic power sensor. The open-circuit voltage output of TENG was registered in different sections of the ultrasonic bath in order to determine the distribution of the acoustic power. TENG electric responses were analyzed by applying the fast Fourier transform (FFT) and fitting the theoretical dependence to experimental data. The main peaks in the frequency spectra of the voltage waveforms corresponded to the fundamental excitation frequency of the ultrasonic bath. TENG device, presented in this paper, can be successfully applied as a self-powered sensor for detection of ultrasonic waves. It enables precise control of the sonochemical process and reduction of power losses of the ultrasonic reactor. 3D printing technology has been confirmed to be fast, easy, and scalable method of fabrication of the ultrasonic sensors.

Ultrasound Velocity-Based Phase Content Measurement of Oil Sludge in Storage Tank

Oil sludge presents a harmful but economically valuable waste. A large amount of oil sludge is produced during the processes of extraction, refining, storage, and transportation of petroleum. The contents of oil, water, and slag in the oil sludge are important parameters that determine the economic value of oil sludge and the choice of oil recovery methods. Most existing phase-content measurement methods can be applied only to the oil-water two-phase mixtures. A simple, low cost, and fast ultrasonic velocity based method is proposed in this paper. The proposed method can realize the three-phase content measurement of oil sludge in storage tanks. First, a semi-empirical model of water content in the oil-water mixture, which describes the relationship between ultrasound velocity and water content in the mixture, is derived. Next, the effect of the temperature on the ultrasound velocity is investigated. Within a certain temperature range, ultrasonic waves in water have different velocity characteristics that depend on temperature than that in oil. Then the effect of the slag on the ultrasound velocity is analyzed experimentally. Based on these effects, a three-phase content measurement method based on ultrasound velocity is proposed. A prototype of three-phase content measurement is developed and experiments are carried out to validate the proposed method. Experimental results show that the proposed method can realize the three-phase content measurement of oil sludge in the storage tank, achieving the root mean square error (RMSE) of the water content of 1.48% and the RMSE of the slag content of 0.73%.

Underwater Ultrasonic Wireless Power Transfer: A Battery-Less Platform for the Internet of Underwater Things

The Internet of Underwater Things (IoUT) will enable new military, scientific, and commercial applications at sea. However, powering of electronic devices in deep water still remains one of the main challenges, since these systems are typically powered by traditional batteries. This article presents the design of the first batteryless underwater sensor node that can be wirelessly recharged through ultrasonic waves from longer distances than allowed by current technologies. First, the architecture of an underwater platform capable of extracting electrical energy from ultrasonic waves is introduced. We then illustrate how to interface this system with an underwater digital communication unit. We discuss the design of a prototype where the storage unit is realized with a batch of supercapacitors. We show through experiments that the harvested energy is sufficient to provide the sensor node with the power necessary to perform a sensing operation and power a modem for ultrasonic communications. In the article, we evaluate the system power transfer efficiency. Given the reduced attenuation of ultrasonic waves in water, we show that our approach can cover longer distances with less transmission power than alternative solutions. Last, we experimentally evaluate the overall operating efficiency of the system.

Broadband ultrasonic focusing in water with an ultra-compact metasurface lens

Focusing of ultrasonic waves in water plays an important role in various scenarios ranging from biomedical imaging to nondestructive testing. Acoustic metasurfaces have been largely explored for acoustic focusing, but they are generally narrowband and mainly implemented for airborne sound because of their structural complexity. Nevertheless, our previous development of metasurfaces provides a great opportunity to solve the challenges. Here, we present numerically and experimentally the broadband focusing of ultrasonic waves in water with a metasurface lens consisting of an array of deep-subwavelength sized and spaced slots. The slot widths of the metasurface are optimized based on microscopic coupled-wave theory. Due to the non-resonant arrangement, the focusing effect is demonstrated over a broad band of frequencies. The metasurface lens with simplicity and an ultra-compact size provides a feasible means for the design of thin and lightweight ultrasonic devices and is suitable for practical applications in biomedical and industrial fields.

Videos of ultrasonic wave propagation through transparent acrylic objects in water for introductory physics courses produced using refracto-vibrometry

This project used refracto-vibrometry to produce full-field videos of ultrasonic wave propagation in water; these videos could be incorporated into high school and college physics courses to illustrate wave behaviors. Refracto-vibrometry (RV) is an interferometric method for optically measuring sound waves. The measurement beam from a Polytec PSV-400 scanning laser Doppler vibrometer was directed through a water tank towards a stationary retroreflective surface. Acoustic wave fronts (density variations) which pass through the measurement laser cause variations in the integrated optical path length. By superimposing tens of thousands of scan points, videos enable visualization of the ultrasound propagation. In one experiment, ultrasonic waves in water (1484 m/s) are incident on a submerged acrylic block at a non-zero angle. The waves are refracted as they travel at about 2700 m/s through the block. Students can determine this speed of sound by measuring the angle of refraction and lateral deflection of the wave fronts in the video. In another experiment, ultrasonic waves passed through an acrylic cylinder, producing a Mach cone in water. Measurement of the Mach cone angle enables determination of the acrylic speed of sound. Links for videos and sample worksheets will be provided.

The control of ultrasonic transmission by the metamaterials structure of electrorheological fluid and metal foam

A metamaterial structure formed by foamed metal and starch and oil-based electrorheological (ER) fluid is designed in this paper. Experiments show that the metamaterial structure exhibits a regulation effect on the amplitude and phase of the transmitted waves of 35–80 kHz ultra-wideband ultrasonic waves in water. With the increase of the electric field, the transmission amplitude and phase of the ultrasonic wave increases, whereas the control ability of the same gradient electric field decreases. The amplitude of the transmission controlled by the metamaterial structure and electric field increases at first, and then decreases with the increase in volume fraction of the ER fluid. Thus, it is thought that the interaction between the microstructure produced by the rheological properties of the ER fluid and the porous foam metal affects the propagation of the acoustic wave.

Study of ultrasonic heat meter measurement error caused by sound attenuation in different water

Along with the rapid development of global economy, energy shortage and environment pollution are getting more and more serious. The implementation of heat metering is an important measure for avoiding energy waste and reducing polluted emission. As the core of heat metering, heat meter must meet the measure heat accuracy according to the"Technical specifications for heat metering of district heating system" (Ministry of Construction). Due to the poor water quality in China, impurities are the main factor that influences the measurement precision of heat meter. The sound attenuation caused by the particles on the propagation path will reduce the measurement accuracy of the ultrasonic heat meter. In this paper, the sound attenuation of ultrasonic wave in water containing impurities which leads to the measuring error of ultrasonic heat meter is studied. The researches in this paper have important scientific significance and practical value.

Ultrasound-assisted water-confined laser micromachining (UWLM) of metals: Experimental study and time-resolved observation

This paper reports the experimental studies and time-resolved observations of the ultrasound-assisted water-confined laser micromachining (UWLM) process on metal workpieces using 532-nm nanosecond laser pulses. UWLM is a new machining process proposed by the corresponding author (Wu, 2014). During UWLM, a laser beam interacts with a workpiece’s front surface location immersed in water to ablate the workpiece, and in-situ ultrasonic waves in water are also applied (for example, from above the front surface using an ultrasonic horn) to the laser ablation site (which energize the water and generate cavitations) to improve the machining process. This paper reports the experimental study of the UWLM process on multiple types of metal workpieces and time-resolved in-situ observations of the process. This kind of study on UWLM has been rarely reported in the literature. Under the studied conditions, it has been found that the ablation depths produced by UWLM at 200 laser pulses are about 2.3–3.8 times the depths by laser ablation in water without ultrasound. Through in-situ time-resolved shadowgraph imaging observations, it has been found that one important likely underlying mechanism for the enhanced material removal rate in the studied UWLM process is that the in-situ ultrasound in UWLM can reduce the material cloud resulted from the previous laser pulse ablation that lingers around laser ablation site, which can enhance the coupling of the subsequent laser pulse(s)’ energy to the workpiece.

Mechanism of the sonochemical production of hydrogen

It has been long recognized that propagation of an ultrasonic wave in water results in hydrogen production. The chemical effects of ultrasound (sonochemistry) originate from acoustic cavitation, that is, the formation, growth and implosive collapse of microscopic bubbles in liquid irradiated by ultrasound wave. Enormous temperatures and pressures are generated within the bubbles at the collapse, making each bubble as a microreactor within which typical flame reactions occur. The combustion in the cavitation bubbles yield species such as OH, H, O, HO2 and others. Although H2 is the most molecular product of water sonolysis, the mechanism of its production is until now not understood and the most reported suggestions are controversial. In this paper, a comprehensive numerical work was carried out, for the first time, to explain the mechanism of ultrasound induced generation of H2 in water. Computer simulations of chemical reactions occurring inside a bubble oscillating in water irradiated by an ultrasonic wave have been performed for different conditions. A kinetics mechanism of 25 reversible chemical reactions was proposed for studying the internal bubble-chemistry. The numerical simulations have evidenced the formation of H2 as well as other products such as O2, H2O2, OH, H, HO2 and O in the bubble during implosion. In all cases, H2 was the main product formed in the bubbles at appreciable amount. Basing on the simulation results and using material balance for hydrogen in the gas and liquid phases, the production rate of H2 in each phase has been quantified. The conclusion was that the main source of H2 production during water sonolysis is the gas phase of the bubbles through the reaction H + OH ↔ H2 + O.

초음파를 이용한 PVA에 의한 다중벽 탄소나노튜브의 수상 그래프팅

초음파를 이용한 수중 반응을 통하여 친수성 고분자인 poly(vinyl alcohol) (PVA)를 다중벽 탄소나노튜브 표면에 개질하였다. 초음파 인가 시 PVA는 라디칼을 지닌 상태로 절단되며 탄소나노튜브는 일반적으로 라디칼 스캐빈저 역할을 하므로 생성된 PVA 라디칼과 반응하여 PVA 사슬이 탄소나노튜브 표면에 그래프트 된다. PVA의 그래프트 반응을 조절하기 위하여 초음파 인가 조건을 300과 500 W로 선택하였으며, 인가 시간은 최대 50분으로 하였다. 탄소나노튜브 표면에 그래프트된 PVA는 FTIR, TGA, SEM, 및 TEM을 통하여 분석하였다. 또한 PVA로 개질된 탄소나노튜브의 분산안정성을 분석하였다. 그래프트된 PVA의 양은 초음파의 인가 출력과 인가 시간에 비례하여 증가하였으며, PVA로 개질된 탄소나노튜브는 물 속에서 매우 안정적인 분산성을 보였다. 이는 복잡한 화학반응 과정없이 초음파를 이용하면 탄소나노튜브를 고분자로 간단히 개질할 수 있음을 보여준다. Multiwall carbon nanotubes (MWCNTs) were modified with a water soluble polymer, poly(vinyl alcohol), PVA, using a simple ultrasonic wave in water. Under the irradiation of ultrasound, PVA chains were severed as macroradicals and instantly grafted onto the surface of MWCNTs due to the radical scavenging effect of MWCNTs. To control the grafting PVA onto MWCNTs, the ultrasonication power and irradiation time were changed from 300 to 500 W and from 10 to 50 min, respectively. The grafted PVA onto MWCNTs was confirmed by FTIR, TGA, SEM, and TEM. Dispersion stability of the modified MWCNTs was monitored by Turbiscan. The amount of grafted PVA on MWCNTs increased with the increase in the sonication power and irradiation time. The grafted PVA on MWCNTs induced the improved dispersion stability of the modified MWCNTs in water. These findings exhibit that ultrasound can be readily used for the grafting polymer chains on MWCNTs.

A study of the nonlinear effects of air bubbles on the ultrasonic field in water

We consider the propagation of ultrasonic waves in water with air bubbles. On the one hand, a numerical model has been developed to analyze the nonlinear effects of the bubbles at high amplitude, in several configurations (open-field, standing waves, 1–D, 2–D, 3–D, homogeneous bubble density, bubble layers, bubble clouds, bubble generation). On the other hand an experimental setup has been constructed and allows us to study the nonlinear behavior of the inertial cavitation field at high frequency and at high power. In particular, a bubble cloud is formed at a large distance from the sonotrode. [Work is part of the research project DPI2008-01429 funded by the Spanish Ministry of Science and Innovation.]

Eigenvalue distributions of correlated multichannel transfer matrices in strongly scattering systems

We experimentally study the effects of correlations in the propagation of ultrasonic waves in water from a multielement source to a multielement detector through a strongly scattering system of randomly placed vertical rods. Due to the strong scattering, the wave transport in the sample is in the diffusive regime. The correlation between the waves is induced when the distance between transducer elements is within the coherence region of the scattered sound. We measure the multichannel transfer matrix $H$, each element of which represents the signal strength between the $m$ individual transmitters and $n$ receivers. The observed eigenvalue distribution of the matrix $H{H}^{\ifmmode\dagger\else\textdagger\fi{}}$ clearly shows the effect of correlations between channels and can be interpreted using random matrix theory. These results are of practical importance in many areas, e.g., for evaluating the information transfer capacity of such a complex scattering system.

Behavior of Solid Particles in Liquid under Ultrasound Irradiation

Utilization of ultrasound is considered as an alternative technique for the separation of particles. The authors studied particle behavior in ultrasonic waves in water with frequencies of 23 kHz or 97 kHz. As a result, the particle aggregation types of bands, clump and points are observed, depending on the frequency, power of ultrasound and particle diameter. It was found that some of the aggregation locations for the clump and the point aggregations are reproducible, respectively.

Measurement of low-frequency ultrasonic wave in water using an acoustic fiber

An acoustic fiber sensor for measurement of ultrasonic waves, which used the approximate Raman-Nath diffraction effect where light diffraction waves were generated in an optical fiber by strain due to the ultrasonic waves, was proposed and examined. In order to characterize the acoustic fiber sensor as a basic study, measurements of low-frequency ultrasonic waves in water were examined using a step index fiber operating as a detection sensor. The results showed that characteristics of detected signals agreed with the theoretical prediction based on Fraunhofer diffraction. This indicates that our proposed fiber sensor can be used for the detection of low-frequency ultrasonic waves as well as the transmission of light diffraction signals.

Measurement of low-frequency ultrasonic wave in water using an acoustic fiber sensor

Measurement of low-frequency ultrasonic wave in water using an acoustic fiber sensor

Topographical Mapping of Surface and Interface Profiles by Using Acoustic Interferometry

The model is presented to explain formation of interference fringes appearing in acoustic images obtained by the acoustic microscopy. In the model, the residual vibration in the vibrator is overlapped by the vibration due to the ultrasonic wave reflected from the surface of the solid. The model was confirmed by the periodical change in the output of the vibrator with the water path. Then acoustic images of an inclined glass plate were observed to examine the influence of the inclination angle, the focal position and the wave frequency on the fringe spacing. A height difference corresponding to the fringe spacing was about a half wavelength of the ultrasonic wave in water. The interference fringes were also observed with a specimen with a deep notch under bending test and showed a good agreement with moire fringes. The presented model suggests that the interference fringes are also formed corresponding to profiles of a reverse surface and a boundary between dissimilar substances. This was confirmed by acoustic images of copper plates with a tapered edge and a shallow groove on the reverse surface, and also those of a copper plate with a dint on the reverse surface, covered by tin alloy solder.

Effect of surfactant on soil removal by ultrasonic wave in water

Effect of surfactant on soil removal by ultrasonic wave in water

The Discrimination Between Water and Oil Using Ultrasonic Sensor

In this paper, we propose the new detection system for discriminating water in oil. The detection method adopts the difference in each temperature characteristic of propagation time of an ultrasonic wave in water and in oil. When water and oil are heated, those propagation times show a completely reverse change. For this reason, this detection system does not need to provide any previous absolute value database as references. We tried to detect the water in the electric oil transformer container. By this experiment result, we found the possibility of discrimination of water in oil, by using the proposed method.

Transmission and Detection of Light Diffraction Signal by Low-Frequency Ultrasonic Wave

Measurement of low-frequency ultrasonic waves in water was examined by the light diffraction effect of a visible laser beam. This laser beam was much narrower than the ultrasonic wavelength. Characteristics of detected signals agreed well with the theoretical prediction based on Fraunhofer diffraction. As shown in the results, light diffraction waves transmitted through a polarization-maintaining fiber could be detected correctly. The results enable us to construct a novel optical fiber sensor which will be used for the detection of low-frequency ultrasonic waves as well as the transmission of light diffraction signals.

Microfluidic amplification of ultrasound with application to MEMS hydrophones

Micro-electro-mechanical systems (MEMS) were used to fabricate a device with passive fluidic components that amplified the motion associated with ultrasonic waves in water. Two types of fluid components were etched in silicon, an acoustic horn, and an acoustic resonator. The fluid motion was detected by a small silicon diaphragm which moved with the sound wave. The diaphragm motion was measured with a laser Doppler vibrometer. Experiments were carried out for acoustic excitations in the frequency region of 0.5 to 5 MHz. Over this frequency range uniform thickness diaphragms were found to support multiple resonance modes and were found to be poor sensing surfaces. Composite diaphragms, with a stiff pedestal supported by compliant edge fixtures, provided a superior sensing surface. The motion of the diaphragm placed at the throat of an acoustic horn demonstrated broadband amplification with a gain of 6. An organ-pipe type resonator provided a narrow-band gain of 3. The horn and resonator structures could be incorporated into most types of MEMS hydrophone devices which use diaphragms to sense sound waves. [Work supported by DARPA.]