• 제목/요약/키워드: Two-Phase PIV

검색결과 45건 처리시간 0.022초

자유표면과 수심깊이가 회전하는 프로펠러 주위 유동에 미치는 영향에 대한 PIV 해석 (PIV Analysis of Free Surface Effects on Flow Around a Rotating Propeller with Varying Water Depth)

  • 백부근;이정엽;이상준
    • 대한조선학회논문집
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    • 제42권5호
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    • pp.427-434
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    • 2005
  • The free surface influenced the wake behind a rotating propeller and its effects were investigated experimentally in a circulating water channel with the variation of water depth. Instantaneous velocity fields were measured using two-frame PIV technique and ensemble-averaged to study the phase-averaged flow structure in the wake region. For an isolated propeller, the flow behind the propeller is affected only by the propeller rotation speed, the leading on the blades and the proximity of the propeller to the free surface. The phase-averaged mean velocity fields show that the potential wake and the viscous wake developed on the blade surfaces. The interaction between the tip vortices and the slipstream causes the oscillating trajectory of tip vortices. The presence of the free surface greatly affected the wake structure, especially for propeller immersion depth of 0.6D. At small immersion depths, the free surface modified the tip and trailing vortices and the slipstream flow structure downstream of X/D = 0.3 in the propeller wake.

PIV시스템을 이용한 규칙파중 2차원 사각형 부유식 구조물 주위의 유동특성 연구 (Experimental Study on Flow Characteristics of Regular Wave Interacting with Rectangular Floating Structure Using PIV Technique)

  • 정광효;전호환
    • 한국해양공학회지
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    • 제20권6호
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    • pp.41-53
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    • 2006
  • This experimental study investigated the flow characteristics for regular waves passing a rectangular floating structure in a two-dimensional wave tank. The particle image velocimetry (PIV) was employed to obtain the velocity field in the vicinity of the structure. The phase average was used to extract the mean flow and turbulence property from repeated instantaneous PIV velocity profiles. The mean velocity field represented the vortex generation and evolution on both sides of the structure. The turbulence properties, including the turbulence length scale and the turbulent kinetic energy budget were investigated to characterize the flow interaction between the regular wave and the structure. The results shaw the vortex generated near the structure corners, which are known as the eddy-making damping or viscous damping. However, the vortex induced by the wave is longer than the roll natural period of the structure, which presents the phenomena opposing the roll damping effect; that is, the vortex may increase the roll motion under the wave condition longer than the roll natural period.

중성자 래디오그래피를 이용한 액체금속 유동장 측정 (Measurement of Liquid-Metal Flow with a Dynamic Neutron Radiography)

  • 차재은;사이토
    • 한국가시화정보학회지
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    • 제9권4호
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    • pp.63-68
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    • 2011
  • The flow-field of a liquid-metal system is very important for the safety analysis and the design of the steam generator of liquid-metal fast breeder reactor. Dynamic neutron radiography (DNR) is suitable for a visualization and measurement of a liquid metal flow and a two-phase flow in a metallic duct. However, the three dimensional DNR techniques is not enough to obtain the velocity information in the wide channel up to now. In this research, a high speed DNR technique was applied to visualize the heavy liquid-metal flow field in the narrow channel with the HANARO-beam facility. The images were taken with a high frame-rate neutron radiography at 250 fps and analyzed with a Particle Image Velocimetry(PIV) method. The images were compared with the results of the commercial CFX code to study the feasibility of DNR technique for the measuring the heavy liquid-metal flow field. The PIV images could discern the turbulent vortex flow in the two-dimensional narrow channel.

식기세척기 내부 유동 분포 분석을 위한 유동가시화 기법 개발 (Development of Flow Visualization Technique for Analysis of Flow Distribution inside Dishwasher)

  • 김아란;함정윤;조진호;조위삼;고한서
    • 한국가시화정보학회지
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    • 제11권2호
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    • pp.12-17
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    • 2013
  • A flow visualization technique was developed to analyze flow distribution inside a dishwasher in this study. Then, a new design plan was proposed to improve the efficiency of the dishwasher by the analyzed results and it was confirmed experimentally by the developed technique. Gas flow fields inside a drying duct of a tub for a drying process was investigated by a developed PIV (Particle Image Velocimetry) and a CFD (Computational Fluid Dynamics) method. Also, the flow visualization technique was developed for the liquid flow field of a rotor-arm system to propose the improved design idea. Also, interactions between liquid and gas were observed around the rotor-arm system. The two-phase flow was modified to the liquid flow field because laser sheets are refracted when pass through the two-phase flow. Thus, the flow visualization techniques was developed in this study to measure the instantaneous flow velocities in the liquid quantitatively.

이산 웨이블릿을 이용한 Bubbly flow의 유통분리기법 (Flow Field Separating Technique in Bubbly Flow using Discrete Wavelet)

  • 조효제;도덕희;최제은;;강병윤
    • 한국항해항만학회지
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    • 제32권10호
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    • pp.777-783
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    • 2008
  • 입자영상속도계(PIV)의 해석에 웨이블릿 변환을 적용하여 정성적인 유동정보뿐만 아니라 공간분해능을 갖는 정량적인 속도장 정보를 제공하고 있다 이 기법은 기포유동(bubbly flow)과 같은 다상(multi-phase)의 유동구조를 해석하는 데도 유용하게 살일 수 있다. 본 연구에서는 기체와 액체의 이상유동(two-pase flow)에 PIV기법을 적용하고 이산 웨이블릿 변환을 사용하여 유장해석을 수행함으로써, 기포를 포함한 속도장 특성과 유동특성을 조사한다.

환형 이젝터 루프 내부의 이상유동특성 파악을 위한 수치해석 및 유동가시화 연구 (Numerical Analysis and Flow Visualization Study on Two-phase Flow Characteristics in Annular Ejector Loop)

  • 이동엽;김윤기;김현동;김경천
    • 한국가시화정보학회지
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    • 제9권4호
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    • pp.47-53
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    • 2011
  • A water driven ejector loop was designed and constructed for air absorption. The used ejector was horizontally installed in the loop and annular water jet at the throat entrained air through the circular pipe placed at the center of the ejector. Wide range of water flow rate was provided using two kinds of pumps in the loop. The tested range of water flow rate was 100${\ell}$ /min to 1,000 ${\ell}$/min. Two-phase flow inside the ejector loop was simulated by CFD analysis. Homogeneous particle model was used for void fraction prediction. Water and air flow rates and pressure drop through the ejector were automatically recorded by using the LabView based data acquisition system. Flow characteristics and air bubble velocity field downstream of the ejector were investigated by two-phase flow visualization and PIV measurement based on bubble shadow images. Overall performance of the two-phase ejector predicted by the CFD simulation agrees well with that of the experiment.

칼새 날개의 비틀림 각에 대한 공력측정 및 PIV 연구 (Aerodynamic Force Measurements and PIV Study for the Twisting Angle of a Swift Wing Model)

  • 복정진;장조원
    • 한국항공우주학회지
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    • 제43권9호
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    • pp.765-772
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    • 2015
  • 칼새 비행의 생체모방 초소형 비행체 적용 가능성을 확인하기 위한 공력측정과 위상동기 PIV 연구가 수행되었다. 2축 회전자유도의 로봇 날개 모델과 불어내기식 풍동을 사용하였다. 비틀림 각은 ${\pm}0$, ${\pm}5$, ${\pm}10$, ${\pm}20$도의 진폭을 갖고, 스트로크각은 90도의 위상차를 갖는 단순조화함수로 변화시켰다. 비틀림 각에 따른 시간에 대한 양력계수 변화는 작은 공력감소와 지연만을 나타내며 주목할 만한 차이를 보이지 않았다. 그러나 항력은 작은 비틀림 각 변화가 큰추력을 생성할 수 있음을 보여주었다. 이러한 것들은 칼새가 비행 중에 작은 비틀림 각을 사용하는 이유를 간접적으로 설명해 준다. PIV연구 결과는 공력지연이 날개주위의 와류구조와 밀접한 관계있다는 것을 보여준다. 이러한 결과는 칼새 모방형 초소형비행체 설계에 있어 비틀림 각은 필수적인 파라미터로서 반드시 고려되어야 함을 의미한다.

VOC 회수를 위한 이젝터 시스템에 관한 수치모사 및 실험적 연구 (Numerical Simulation and Experimental Study on an Ejector System for VOC Recovery)

  • 김현동;이동엽;김윤기;정원택;안주하;김경천
    • 한국가시화정보학회지
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    • 제9권2호
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    • pp.54-60
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    • 2011
  • This paper is a basic study on volatile organic compounds(VOC) recovery system in a crude oil carrier. VOC is easily evaporated in cargo tankers during loading and transportation of crude oil, causes serious environmental contamination and a huge economic loss. An ejector system is designed to mix VOC gas into crude oil flow to reduce VOC concentration. Detail two-phase flow inside the ejector is simulated using a commercial CFD code. To verify the numerical prediction, a scale-down experiment is conducted. Instead of crude oil and VOC, water and air are used as the working fluids. Flow characteristics and main parameters are obtained by two-phase flow visualization and PIV measurements. Air volume flow rate induced by the ejector is compared with respect to the volume flow rate of water using experimental and numerical results. Overall performance of the two-phase ejector predicted by the CFD simulation agrees well with that of the experiment.

A Study on the Characteristics of Two-Phase Flow by Driven Bubbles in a Liquid Bath

  • Oh, Yool-Kwon;Seo, Dong-Pyo
    • International Journal of Air-Conditioning and Refrigeration
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    • 제13권1호
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    • pp.44-50
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    • 2005
  • In the present study, the characteristics of upward bubble flow were experimentally investigated in a liquid bath. An electro-conductivity probe was used to measure local volume fraction and bubble frequency. Since the gas was concentrated at the near the nozzle, the flow parameters were high near the nozzle. In general their axial and radial values tended to decrease with increasing distance. For visualization of flow characteristics, a Particle Image Velocimetry (PIV) and a thermo-vision camera were used in the present study. The experimental results showed that heat transfer from bubble surface to water was largely completed within z = 10 mm from the nozzle, and then the temperature of bubble surface reached that of water rapidly. Due to the centrifugal force, the flow was more developed near the wall than at bubble-water plume. Vortex flow in the bottom region was relatively weaker than that in the upper region.

Research of liquid-solid two phase flow in centrifugal pump with crystallization phenomenon

  • Liu, Dong;Wang, Ya-Yun;Wang, Ying-Ze;Wang, Chun-Lin;Yang, Min-Guan
    • International Journal of Fluid Machinery and Systems
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    • 제7권2호
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    • pp.54-59
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    • 2014
  • Particle Image Velocimetry combined with developed image processing method is adopted to study the liquid-solid two phase flow in the centrifugal pump impeller with crystallization phenomenon. The tracer particle is used to follow the liquid phase, which has the diameter between 8 to $12{\mu}m$. The crystal particle precipitates from the sodium sulfate solution does change the wavelength of the laser, and which has great laser scattering characteristics. The diameter of the crystal particle is larger than $20{\mu}m$. Through calculating the diameter of the particles in the image, the tracer particle and the crystal particle can be distinguished. By analyzing the experimental result, the following conclusion has been obtained. During the delay period, there is not any crystal particle and the pump performance has not been changed. As the crystallization process begins, the crystal nuclei appears from the supersaturation solution and grows larger with temperature decreasing, which has the tendency of moving towards the pressure side. The characteristics of liquid-solid two phase flow with crystallization phenomenon in the pump are obtained according to analysis of experimental results, and some guiding advices are presented to mitigate the crystallization phenomenon in pump impeller.