• Title/Summary/Keyword: wave separation

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Study on active vibration control based on wave viewpoint using the longitudinal wave separation method (종파 분리 방법을 이용한 파동 관점의 능동 진동 제어)

  • Jung, Byung-Bo;Park, Young-Jin;Park, Youn-Sik
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.05a
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    • pp.928-933
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    • 2007
  • In this research, we investigated active vibration control based on wave-viewpoint using the longitudinal wave separation method. The control strategy is the one of active vibration control technique for generating vibration reduced zone and uses wave information including the directivity as the cost function. In order to get the wave information from the measured values, we proposed and examined the time-domain longitudinal wave separation method proper to real time application like active vibration control. Using the proposed method, we examine the performance and feasibility of active vibration control based wave view-point through the simulation. The related experimental verification and application is going to be expected in a near future.

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Continuous Microalgae Separation Process Using Ultrasonic Waves (초음파를 이용한 미세조류 연속분리공정)

  • Kim, Sung Bok;Jeong, Sang Hwa
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.24 no.4
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    • pp.407-413
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    • 2015
  • Research for renewable energy is being performed since it has the merits of little pollution of the environment and sustainable energy resources. Microalgae is attractive as a renewable energy resource. Biomass of the microalgae can be produced by mass culturing, and bulk harvest technology of is needed to produce biomass continuously. Recently, ultrasonic waves were used to harvest the cultivated microalgae continuously. In this study, the separation process using ultrasonic waves was performed to effectively harvest the microalgae. An ultrasonic wave separation resonator was designed and manufactured based on the acoustic field analysis. Separation experiments using design of experiment were carried out, and the influence of experimental variables from the ultrasonic wave separation process was investigated. Mixing conditions of variables were estimated to obtain high separation efficiency and a large microalgae harvest. Experimental results for suitable mixing conditions were compared with simulation results calculated from the state equation.

Shock-Wave Oscillation in a Supersonic Diffuser -Displacement Measurement of Mormal Shock-Wave- (초음속 디퓨져에서 충격파의 진동 (1) -수직충격파의 순간변위 측정-)

  • 김희동;엄용균;권순범
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.4
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    • pp.933-945
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    • 1994
  • A shock-wave in a supersonic flow can be theoretically determined by a given pressure ratio at upstream and downstream flowfields, and then the obtained shock-wave is stable in its position. Under the practical situation in which the shock-wave interacts with the boundary layer along a solid wall, it cannot, however, be stable even for the given pressure ratio being independent of time and oscillates around a time-mean position. In the present study, oscillations of a weak normal shock-wave in a supersonic diffuser were measured by a Line Image Sensor(LIS), and they were compared with the data of the wall pressure fluctuations at the foot of the shock-wave interacting with the wall boundary layer. LIS was incorporated into a conventional schlieren optical system and its signal, instantaneous displacement of the interacting shock-wave, was analyzed by a statistical method. The results show that the displacement of an oscillating shock-wave increase with the upstream Mach number and the dominant frequency components of the oscillating shock-wave are below 200 Hz. Measurements indicated that shock-wave oscillations may not entirely be caused by the boundary layer separation. The statistical properties of oscillations appeared, however, to be significantly affected by shock-induced separation of turbulent boundary layer.

Hydrodynamic scene separation from video imagery of ocean wave using autoencoder (오토인코더를 이용한 파랑 비디오 영상에서의 수리동역학적 장면 분리 연구)

  • Kim, Taekyung;Kim, Jaeil;Kim, Jinah
    • Journal of the Korea Computer Graphics Society
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    • v.25 no.4
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    • pp.9-16
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    • 2019
  • In this paper, we propose a hydrodynamic scene separation method for wave propagation from video imagery using autoencoder. In the coastal area, image analysis methods such as particle tracking and optical flow with video imagery are usually applied to measure ocean waves owing to some difficulties of direct wave observation using sensors. However, external factors such as ambient light and weather conditions considerably hamper accurate wave analysis in coastal video imagery. The proposed method extracts hydrodynamic scenes by separating only the wave motions through minimizing the effect of ambient light during wave propagation. We have visually confirmed that the separation of hydrodynamic scenes is reasonably well extracted from the ambient light and backgrounds in the two videos datasets acquired from real beach and wave flume experiments. In addition, the latent representation of the original video imagery obtained through the latent representation learning by the variational autoencoder was dominantly determined by ambient light and backgrounds, while the hydrodynamic scenes of wave propagation independently expressed well regardless of the external factors.

Effects of demi-hull separation ratios on motion responses of tidal current turbines-loaded catamaran

  • Junianto, Sony;Mukhtasor, Mukhtasor;Prastianto, Rudi Walujo;Jo, Chul Hee
    • Ocean Systems Engineering
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    • v.10 no.1
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    • pp.87-110
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    • 2020
  • Catamaran has recently been a choice to support a typical vertical axis turbine in floating tidal current energy conversion system. However, motion responses associated with the catamaran can reduce the turbines efficiency. The possibility to overcome this problem isto change the catamaran parameter by varying and simulating the demi-hull separations to have lower motion responses. This simulation was undertaken by Computational Fluid Dynamic (CFD) using potential flow analysis. Cases of demi-hull separation were considered, with ratios of demi-hull separation (S) to the breadth of demi-hull (B), S/B of 3.45, 4.95, 6.45, 7.2 and 7.95. In order to compare to the previous works in the literature, the regular wave was set with wave height of 0.8 m. Furthermore, the analysis was carried out by irregular waves with significant wave height, Hs, of about 0.09 to 1.5 m and the wave period, T, of about 1.5 to 6 s or corresponding to the wave frequency, ω, of about 1.1 to 4.2 rad/s. The wave spectrum was derived from the equation of the International Towing Tank Conference (ITTC). For the case of turbines-loaded catamaran under consideration, the new finding is that the least significant amplitude response can be satisfied at the ratio S/B of 7.2. This study indicates that selecting a right choice of demi-hull separation ratio could contribute in reducing motion responses of the tidal current turbines-loaded catamaran.

Characteristics of Particle Separation in Suspension using an Ultrasonic Standing Wave

  • Shin, Beom-Soo;Danao, Mary-Grace C.
    • Journal of Biosystems Engineering
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    • v.37 no.2
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    • pp.113-121
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    • 2012
  • Purpose: Particle separation in solution is one of important process in a unit operation as well as in an extract preparation for biosensors. Contrary to centrifuge-type of mesh-type filter, using an ultrasonic standing wave make the filtering process continuous and free from maintenance. It is needed to investigate the characteristics of particle movement in the ultrasonic standing wave field. Methods: Through the computer simulation the effects of major design and driving parameters on the alignment characteristics of particles were investigated, and a cylindrical chamber with up-stream flow type was devised using two circular-shape PZTs on both sides of the chamber, one for transmitting ultrasonic wave and the other for just reflecting it. Then, the system performance was experimentally investigated as well. Results: The speed of a particle to reach pressure-node plane increased as the acoustic pressure and size of particle increased. The maximum allowable up-stream flow rate could be calculated as well. As expected, exact numbers of pressure-node planes were well formed at specific locations according to the wavelength of ultrasonic wave. As the driving frequency of PZT got close to its resonance frequency, the bands of particles were observed clearer, which meant the particles were trapped into narrower space. Higher excitation voltages to the PZT produced a greater acoustic force with which to trap particles in the pressure-node planes, so that the particles gathered could move upwards without disturbing their alignments even at a higher inlet flow rate. Conclusions: This research showed the feasibility of particle separation in solution in the continuous way by an ultrasonic standing wave. Further study is needed to develop a device to collect or harvest those separated particles.

Comparison of Edge Wave Normal Modes (Edge Wave 고유파형의 비교)

  • Seo, Seung Nam
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.25 no.5
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    • pp.285-290
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    • 2013
  • Both full linear and shallow water edge waves are compared to get a better understanding of edge wave behavior. By using method of separation of variables, we are able to get solution of full linear edge wave presented by Ursell (1952) without derivation. The shallow water edge waves show dispersive features despite being derived from shallow water equations. When bottom slope is mild enough, shallow water edge wave tends to linear edge wave and has some advantages of manipulation. Solution of edge wave generated by a moving landslide of Gaussian shape is constructed by an expansion of shallow water normal modes. Numerical results are presented and discussed on their main features.

Numerical Study on the Suppression of Shock Induced Separation on a Strongly Heated Wall (강하게 가열된 벽면 위에서 충격파에 의한 경계층 박리의 제거에 관한 수치 연구)

  • LEE Doug-Bong;SHIN Joon-Cheol
    • Journal of computational fluids engineering
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    • v.2 no.2
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    • pp.59-72
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    • 1997
  • A numerical model is constructed to simulate the interactions of oblique shock wave / turbulent boundary layer on a strongly heated wall. The heated wall temperature is two times higher than the adiabatic wall temperature and the shock wave is strong enough to induce boundary layer separation. The numerical diffusion in the finite volume method is reduced by the use of a higher order convection scheme(UMIST scheme) which is a TVD version of QUICK scheme. The turbulence model is Chen-Kim two time scale model. The comparison of the wall pressure distribution with the experimental data ensures the validity of this numerical model. The effect of strong wall heating enlarges the separation region upstream and downstream. In order to eliminate the separation, wall suction is applied at the shock foot position. The bleeding slot width is about same as the upstream boundary layer thickness and suction mass flow is 10% of the flow rate in the upstream boundary layer. The final configuration of the shock reflection pattern and the wall pressure distribution approach to the non-viscous value when wall suction is applied.

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Investigation on the shock-induced rocket separation from the mother plane (충격파에 의한 비정상 모선분리 현상 연구)

  • Kim Y. S.;Ji Y. M.;Lee J.-W.;Park J. S.
    • 한국전산유체공학회:학술대회논문집
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    • 2004.10a
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    • pp.155-160
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    • 2004
  • This paper describes a supersonic separation of air-launching rocket from the mother plane. Three dimensional Euler equations were numerically solved to analyze steady/unsteady state fluid flows. To solve the Euler equations, named CFD-FASTRAN that is commercial computation code. The results of simulation clearly demonstrate effect of shock-expansion wave interaction between the rocket and the mother plane. Moreover, important influential factors at separating stage of the rocket were extracted with a comprehensive analysis. Finally, from the consideration of supersonic-separation, a guideline to safety-separation is given to the design of supersonic air-launching rocket.

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NUMERICAL INVESTIGATION ON THE SAFE SUPERSONIC AIR-LAUNCHING ROCKET SEPARATION FROM THE MOTHER PLANE (안전한 초음속 공중발사를 위한 삼차원 로켓 주위의 모선분리 유동 해석)

  • Ji Y.M.;Lee J.W.;Park J.S.
    • 한국전산유체공학회:학술대회논문집
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    • 2005.10a
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    • pp.255-259
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    • 2005
  • An analysis is made of flow and rocket motion during a supersonic separation stage of air-launching rocket from the mother plane. Three-dimensional Euler and Navier-Stokes equations are numerically solved to analyze the steady/unsteady flow field around the rocket which is being separated from two cases of mother plane configuration: one is an idealized ogive-cylinder body and the other is a real F-4E Phantom. The simulation results clearly demonstrate the effect of shock-expansion wave interaction between the rocket and the mother plane. As a result, a design-guideline of supersonic air-launching rocket for the safe separation is proposed.

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