Papers by Keyword: Acoustic Pressure

Abstract: This paper deals with the problem of visualization of the widely known and of considerable practical value problem of sound wave propagation in a liquid medium containing gas bubbles. The study was carried out using modern methods of computer simulation in the COMSOL Multiphysics software environment, which provides extensive opportunities for numerical analysis of complex physical processes. In the course of the study, a set of calculations was performed, which made it possible to obtain a series of illustrative images reflecting the distribution of acoustic and sound pressure both in the volume of the water medium and on the boundary surfaces at different sound frequencies. The constructed model demonstrated its efficiency, allowing to identify areas with increased and decreased acoustic pressure formed on the surface of air bubbles under the influence of sound waves. Visualization of these processes opens up opportunities for analysis and optimization of acoustic systems operating in the presence of gas inclusions in the liquid.

Abstract: The article addresses the problem of noise from the perspective of protected building space near the construction. If they are near a building already populated, the residents should not be exposed to elevated noise burden, and according to Government Regulation No. 272/2011 of 24 August 2011 on health protection before adverse effects of noise and vibrations, which are set noise limits. In the process optimization production planning is therefore necessary to address the areas of in-situ noise, its creation, modeling, design methodologies to assess the overall noise at the site. The Article analyzed the issue introduction of new approaches when optimizing for the site and the necessity aspects of noise pollution site in construction technological preparations for the construction. The article defines in detail the sources of noise during construction, dealing with modeling of site noise sources and the value of the protected space structures. It presents examples of noise studies, where captured effect of noise on the nearest places protected sites and residential areas. Presents the methodology of work with the values of the inputs and outputs when working with software support.

Abstract: In this paper, we present an acoustic-structure couple interaction model of partial discharge (PD) in Gas Insulated Switchgear, the interaction between the internal acoustic source of partial discharge and structure of GIS is simulated with the finite element analysis, and the internal and external acoustic pressure levels distribution of GIS is obtained. The results based on the frequency sweep shown that the internal acoustic pressure levels is bigger than the external acoustic pressure levels of GIS in the ultrasonic frequency spectrum,it suggests that it should use the ultrasonic sensor with a broadband spectrum response to measure partial discharge in GIS, which can obtain high sensitivity. In addition, the external sound pressure of GIS is very small, and the signal of the Ultrasonic sensors must be amplified for measurement. Meanwhile, the outside acoustic pressure of the epoxy insulator is so small that it can properly judge the adjacent GIS unit partial discharge conditions.

Abstract: With the increase in traffic density and speed of motor vehicles tire noise became an important area of research. A number of researchers have worked in the last decade to understand noise due to tires. It is important to identify different noise generation mechanisms that contribute to the tire noise and find a way to reduce it. In the present study, the noise generated by the acoustic cavity of the tire is taken into consideration. A non-linear finite element (FE) model using Abaqus has been developed for determining the acoustic pressure in the air cavity, when subjected to harmonic excitation. The influence of the inflation pressure and vehicle load on the tire acoustic cavity is studied for a passenger car radial tire (PCR) 175/70R13.

Abstract: This study focused on observing the melting phenomena and investigated a principle factor of enhanced heat transfer in phase change material when the ultrasonic vibrations were applied during the melting process. For visualization, particle image velocimetry and thermal-vision camera for observing the flow phenomenon was used. Also, experiments were performed to obtain the experimental results such as melting time and temperature distribution. Besides, structural vibration simulator which is applying a coupled finite element-boundary element method (Coupled FE-BEM) was used for calculation of acoustic pressure occurred by ultrasonic vibrations in liquid region. The results of experimental and numerical observations show that acoustic streaming induced by ultrasonic vibrations is one of the prime effects acoustically enhanced phase change heat transfer and help to accelerate the melting of phase change material. Also, the application technique of visualization and computational simulation introduced in this study is very useful and important to analyze the mechanical behavior of material in a fast fluid dynamic or acoustic field.

Abstract: The present study was experimentally investigated the effect of ultrasonic vibrations on boiling heat transfer augmentation during the heating process. The experiments were carried out under the constant wall temperature condition and were divided into two cases applying with and without ultrasonic vibrations, respectively. Also, the temperature distributions in a vessel filled with water were measured using thermocouples during the heating process, heat transfer coefficient and augmentation ratio of heat transfer on states of convection, subcooled boiling and saturated boiling were calculated from obtained temperature profiles. In addition, the profiles of pressure variations measured using a hydrophone were compared with the augmentation ratio of heat transfer in acoustic fields. The results of experimental study were revealed that general profiles of heat transfer coefficient and augmentation ratio of heat transfer is more increased the convection state than the others states. Moreover, the profiles of acoustic pressure is relatively higher near ultrasonic transducer than other points where is no installed it and affects the augmentation ratio of heat transfer. In the end, as well as known “acoustic streaming” induced by ultrasonic vibrations is one of the prime effects acoustically augmented boiling heat transfer or phase change heat transfer.

Abstract: The present study is investigated the causes of enhanced heat transfer during the melting process of solid-liquid PCM (Phase Change Material) using an ultrasonic vibration. Paraffin (noctadecane) was selected as a PCM and experimental studies were performed as following. Heat transfer coefficient and enhancement ratio of heat transfer was measured, acoustic streaming induced by ultrasonic waves observed using a PIV (Particle Image Velocimetry) and thermally oscillating flow phenomenon observed using an infrared thermal camera during the melting process. For the numerical study, a coupled FE-BEM (Finite Element-Boundary Element Method) was applied to investigate acoustic pressure occurred by acoustic streaming in a medium. And then, the profiles of pressure variation compared with the enhancement ratio of heat transfer. The results of this study revealed that ultrasonic vibrations accompanied the effects like acoustic streaming and thermally oscillating flow. Such effects are a prime mechanism in the overall melting process when ultrasonic vibrations are applied. Also, as the acoustic pressure occurred by acoustic streaming increases, the higher enhancement ratio of heat transfer is obtained.

Abstract: The present study was investigated on the melting phenomena and the accelerative factors of phase change material (PCM) by acoustic streaming induced ultrasonic vibrations. To investigate the melting phenomena and accelerative factors, the experimental study was measured the liquid temperature and melting time of PCM and was observed the velocity vectors and thermal fluid flow induced acoustic streaming to investigate the heat transfer using particle image velocimetry (PIV) and infrared thermo vision camera, respectively. Also, the numerical study based on a coupled finite element-boundary element method (Coupled FE-BEM) was performed to investigate the analysis of pressure field in the PCM. The results of experimental works revealed that acoustic streaming observed by PIV and infrared thermo vision camera is one of the prime effects accelerating phase change heat transfer. And, the final temperature of PCM is lower and melting speed is 2.6 times faster than that without ultrasonic vibrations when ultrasonic vibrations are applied. The results of numerical work presented that acoustic pressure is higher near the ultrasonic transducer than other points where no ultrasonic transducer was installed and develops more intensive flow such as acoustic streaming, destroying the flow instability. Moreover, the profile of acoustic pressure variation is consistent with that of enhancement of heat transfer.

Abstract: This paper presents the theory, design, and evaluation of a smart device for the enhanced separation of particles mixed in fluid. The smart device takes advantage of the ultrasonic standing wave, which was generated by the operation of a piezoceramic PZT patch installed in the smart device. The details of the device design including the electro-acoustical modelling for separation and PZT transducer are described at first. Based on this design, the separation device was fabricated and evaluated. In the experiments, an optical camera with a zoom lens was used to monitor the position of particles within the separation channel layer in the device. The electric impedance of the PZT patch bonded on the separation device was measured .The device shows a strong levitation and separation force against 50μm diameter particles mixed with water at the separation channel in the device. Experimental results also showed that the device can work at both heavy and light sand particles mixed with water due to the generated standing wave field in the separation channel.