와류기인진동을 이용한 신재생에너지 발전에서 유체력 추정연구

박홍래 한국신·재생에너지학회 2023 신재생에너지 Vol.19 No.2

Vortex-induced vibrations are a type of flow-induced vibrations caused by alternating lift forces. With increasing demandfor renewable energy, the application of vortex-induced vibrations to renewable energy has been widely studied. Vortex-inducedvibrations for aquatic clean energy (VIVACE) converter is a renewable energy device that generates electricity from rivers or oceansusing vortex-induced vibrations. To increase the design life and power harnessing capacity of the VIVACE converter, the estimationof fluid forces due to vortex-induced vibrations is essential. Herein, vortex-induced vibrations were experimentally tested, and theiramplitude and frequency response were measured. The amplitude results showed four different branches: initial branch, upper branch,lower branch, and desynchronization range. According to the fluid force coefficient results, the maximum lift coefficient occurred atthe upper branch. Additionally, a mathematical model is proposed to estimate fluid forces due to vortex-induced vibrations withoutusing measurement devices. This mathematical model enables the estimation of fluid force coefficients and phase lag using amplitudeand frequency response of vortex-induced vibrations.

Non-contact monitoring of 3-dimensional vibrations of bodies using a neural network

Ha, Sung Chul,Cho, Gyeong Rae,Doh, Deog-Hee The Korean Society of Marine Engineering 2015 한국마린엔지니어링학회지 Vol.39 No.10

Gas piping systems in power plants and factories are always influenced by the mechanical vibrations of rotational machines such as pumps, blowers, and compressors. Unusual vibrations in a gas piping system influence possible leakages of liquids or gases, which can lead to large explosive accidents. Real-time measurements of unusual vibrations in piping systems in situ prohibit them from being possible leakages owing to the repeated fatigue of vibrations. In this paper, a non-contact 3-dimensional measurement system that can detect the vibrations of a solid body and monitor its vibrational modes is introduced. To detect the displacements of a body, a stereoscopic camera system is used, through which the major vibration types of solid bodies (such as X-axis-major, Y-axis-major, and Z-axis-major vibrations) can be monitored. In order to judge the vibration types, an artificial neural network is used. The measurement system consists of a host computer, stereoscopic camera system (two-camera system, high-speed high-resolution camera), and a measurement target. Through practical application on a flat plate, the measured data from the non-contact measurement system showed good agreement with those from the original vibration mode produced by an accelerator.

Non-contact monitoring of 3-dimensional vibrations of bodies using a neural network

하성철,도덕희,조경래 한국마린엔지니어링학회 2015 한국마린엔지니어링학회지 Vol.39 No.10

Gas piping systems in power plants and factories are always influenced by the mechanical vibrations of rotational machines such as pumps, blowers, and compressors. Unusual vibrations in a gas piping system influence possible leakages of liquids or gases, which can lead to large explosive accidents. Real-time measurements of unusual vibrations in piping systems in situ prohibit them from being possible leakages owing to the repeated fatigue of vibrations. In this paper, a non-contact 3-dimensional measurement system that can detect the vibrations of a solid body and monitor its vibrational modes is introduced. To detect the displacements of a body, a stereoscopic camera system is used, through which the major vibration types of solid bodies (such as X-axis-major, Y-axis-major, and Z-axis-major vibrations) can be monitored. In order to judge the vibration types, an artificial neural network is used. The measurement system consists of a host computer, stereoscopic camera system (two-camera system, high-speed high-resolution camera), and a measurement target. Through practical application on a flat plate, the measured data from the non-contact measurement system showed good agreement with those from the original vibration mode produced by an accelerator.

Vibration Measurements in the Mining Industry Applying the Software Install Application to the Kosovo Energy Corporation

Luzha, Ibush,Baftiu, Naim,Maloku, Betim,Qarkaxhija, Jusuf International Journal of Computer ScienceNetwork S 2022 International journal of computer science and netw Vol.22 No.8

The assessment of specific impacts on the environment is a preventive measure for environmental protection which is based on the definition and proposal of measures that can prevent harmful effects, reduce or eliminate them. In the physical sense, vibration is the oscillating motion of an object with the effect of internal or external forces applied to it. People who touch a vibrating surface or object will feel these vibrations. In general, there are two types of vibration exposure. The first are the vibrations of the hands and arms transmitted by the held parts of tools or machinery. The second are whole-body vibrations transmitted from a seat or surface to a motorized car. The risk of injury to workers exposed to vibration varies depending on the size, frequency, type, duration of exposure, and organ affected. The purpose of this paper is to review the measurements of vibrations in the Kosovo Energy Corporation in the mine Sibovc Southwest, where coal with a rotary excavator is exploited and the evaluation of vibrations for working conditions for workers working in that environment and improving working conditions for the measurement of vibrations we have used the device Minimate DS 078, the purpose of such environmental impact assessment is to collect data and predict the harmful impacts on the environment, namely the impact on water, air, soil, life and health of as well as identify and propose measures that could prevent, reduce or eliminate altogether.

Monitoring and control of wind-induced vibrations of hanger ropes of a suspension bridge

Xu G. Hua,Zheng Q. Chen,Xu Lei,Qin Wen,Hua W. Niu 국제구조공학회 2019 Smart Structures and Systems, An International Jou Vol.23 No.6

In August 2012, during the passage of the typhoon Haikui (1211), large amplitude vibrations were observed on long hangers of the Xihoumen suspension Bridge, which destroyed a few viscoelastic dampers originally installed to connect a pair of hanger ropes transversely. The purpose of this study is to identify the cause of vibration and to develop countermeasures against vibration. Field measurements have been conducted in order to correlate the wind and vibration characteristics of hangers. Furthermore, a replica aeroelastic model of prototype hangers consisting of four parallel ropes was used to study the aeroelastic behavior of hanger ropes and to examine the effect of the rigid spacers on vibration mitigation. It is shown that the downstream hanger rope experiences the most violent elliptical vibration for certain wind direction, and the vibration is mainly attributed to wake interference of parallel hanger ropes. Based on wind tunnel tests and field validation, it is confirmed that four rigid spacers placed vertically at equal intervals are sufficient to suppress the wake-induced vibrations. Since the deployment of spacers on hangers, server hanger vibrations and clash of hanger ropes are never observed.

Superharmonic vibrations of sandwich beams with fibre composite core layer based on the multiple scale method

Abbache Ali,Hadj Youzera,Moussa Abualnour,Mohammed Sid Ahmed Houari,Sid Ahmed Meftah,Abdelouahed Tounsi 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.80 No.2

This paper deals with the secondary vibration problem in the superharmonic case near the harmonic excitation of 1/3ωl, arising from the vibration nonlinearity that characterizes the slender and less damping laminated beam with composite material core. For this aim the multiple scale method in conjunction with the higher order zigzag theories are used to obtain the resonance responses. In the present work the nonlinear forced vibration problem of sandwich beams under harmonic excitation is solved by the multiples scales method, based by the introduction of an artificial parameter with higher order expansions, to control the nonlinear analytical solutions. The application of this method demonstrates the sensitivity of the sandwich beams with viscoelastic composite layer to the secondary superharmonic vibrations. Following, parametric study is conducted to demonstrate the vulnerability of the laminated structures to the superharmonic vibrations and to reduce as far as possible the amplitude vibrations achieved by more appropriated structural design. The results reveal the effect of the slenderness of the sandwich beams on the hardening changes. In the other hand the results demonstrate the importance of fibre orientation angle to reduce as far as possible the amplitude responses of the sandwich structures in superharmonic vibration case.

Guided wave formation in coal mines and associated effects to buildings

Guzin G. Uyar,Ezel Babayigit 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.60 No.6

The common prospect in diminishing mine-blast vibration is decreasing vibration with increasing distance. This paper indicates that, contrary to the general expectancy, vibration waves change their forms when they are travelling through the low velocity layer like coal and so-called guided waves moving the vibration waves to longer distances without decreasing their amplitudes. The reason for this unexpected vibration increase is the formation of guided waves in the coal bed which has low density and low seismic velocity with respect to the neighboring layers. The amplitudes of these guided waves, that are capable of traveling long distances depending on the seam thickness, are several times higher than that of the usual vibration waves. This phenomenon can many complaints from the residential areas very far away from the blasting sites. Thus, this unexpected behavior of the coal beds in the surface coal mines should also be considered in vibration minimization studies. This study developed a model to predict the effects of guided waves on the propagation ways of blast-induced vibrations. Therefore, vibration mitigation studies considering the nearby buildings can be focused on these target places.

가공정도 향상을 위한 Glass Cutting Machine의 설계 개선

권인환(In-Hwan Kwon),노승훈(Seung-Hoon Ro),박유라(Yu-Ra Park),이일환(Il-Hwan Yi),길사근(Sa-Geun Kil),박근우(Keun-Woo Park) 한국기계가공학회 2014 한국기계가공학회지 Vol.13 No.3

Touch panels are widely used in the modern display industry as the cover glass of smart mobile phones and tablet PCs. Glass cutting machines are commonly used to cut the panels into their proper sizes. Vibration of these glass cutting machines is assumed to be the main factor leading to the creation of burrs, notches, cracks, scratches and chips on the cut surfaces, eventually causing defects of the cover glass. In this study, the vibrations of a glass cutting machine used for the shearing of cover glass components were analyzed through an experiment and a computer simulation. The structural properties leading to vibration were also analyzed in an effort to determine design alterations which can suppress these vibrations. Moreover, each design alteration was applied to a computer simulation model to determine the effect of different alteration on suppressing vibration. The results show that simple design alterations can substantially suppress vibrations of glass cutting machines

Damage prevention and aerodynamics of cable-stayed bridges in heavy snowstorms: A case study

Mladen Bulić,Mehmed Čaušević 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.85 No.1

This paper begins by analyzing cable vibrations due to external excitations and their effects on the overall dynamic behavior of cable-stayed bridges. It is concluded that if the natural frequency of a cable approaches any natural frequency of the bridge, the cable loses its rigidity and functionality. The results of this analysis explain the phenomenon that occurred on the Dubrovnik Bridge in Croatia during a storm and measures for its retrofit. A field test was conducted before the bridge was opened to traffic. It was concluded: “The Bridge excited unpleasant transverse superstructure vibration with the frequency of approximately 0.470 Hz. Hence, it seems possible that a pair of stays vibrating in phase may excite deck vibrations”. Soon after this Bridge opened, a storm dumped heavy damp snow in the area, causing the six longest cable stay pairs of the main span to undergo large-amplitude vibrations, and the superstructure underwent considerable displacements in combined torsion-sway and bending modes. This necessitated rehabilitation measures for the Bridge including devices to suppress the large-amplitude vibrations of cables. The rehabilitation and monitoring of the Bridge are also presented here.

Vibration of a string against multiple spring-mass-damper stoppers

Shin, Ji-Hwan,Talib, Ezdiani,Kwak, Moon K. Elsevier 2018 Journal of sound and vibration Vol.414 No.-

<P><B>Abstract</B></P> <P>When a building sways due to strong wind or an earthquake, the elevator rope can undergo resonance, resulting in collision with the hoist-way wall. In this study, a hard stopper and a soft stopper comprised of a spring-mass-damper system installed along the hoist-way wall were considered to prevent the string from undergoing excessive vibrations. The collision of the string with multiple hard stoppers and multiple spring-mass-damper stoppers was investigated using an analytical method. The result revealed new formulas and computational algorithms that are suitable for simulating the vibration of the string against multiple stoppers. The numerical results show that the spring-mass-damper stopper is more effective in suppressing the vibrations of the string and reducing structural failure. The proposed algorithms were shown to be efficient to simulate the motion of the string against a vibration stopper.</P>