• Title/Summary/Keyword: YAG

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Experimental study on the natural convection in an enclosure with an adiabatic body using the two-color LIF method (Two-color LIF 기법을 이용한 단열체가 있는 밀폐계 내에서의 자연대류에 관한 실험적 연구)

  • Kwon Su Hyun;Jeong Eun Ho;Kim Kyung Chun
    • 한국가시화정보학회:학술대회논문집
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    • 2004.11a
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    • pp.104-107
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    • 2004
  • Most of the previous studies on natural convection were based on the numerical analysis, and some experimental studies considered the classic case of thermal convection. In this study, an adiabatic square body was located at the center of an enclosure between the bottom hot and top cold walls. And the measurement of the detailed temperature fields was conducted by the method of two-color Laser Induced Fluorescence using a Nd:Yag laser. As a result, heat transfer characteristics of natural convection with an adiabatic body was estimated as a function of time over a range of Rayleigh numbers.

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4-Dimensional Particle Tracking Velocimetry (4D-PTV)

  • Doh Deog Hee;Hwnag Tae Gyu;Cho Yong Beom;Pyeon Yong Beom;Okamoto Koji
    • 한국가시화정보학회:학술대회논문집
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    • 2003.11a
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    • pp.43-44
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    • 2003
  • A 4D-PTV system was constructed. The measurement system consists of three high-speed high-definition cameras, Nd-Yag laser and a host computer. The GA-3D-PTV algorithm was used for completing the measurement system. A horizontal impinged jet flow was measured. The Reynolds number is about 40,000. Spatial temporal evolution of the jet flow was examined and physical properties such as spatial distributions of vorticity and turbulent kinetic energy were obtained with the constructed system.

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Simultaneous Measurements of Velocity Fields at Two Vertically Crossing Planes by PIV Systems Using Polarization Technique (편광기법을 이용한 수직교차평면의 PIV 속도장 동시측정)

  • Kim Sang Moon;Yoon Sang Youl;Kwon Sung Hoon;Kim Kyung Chun
    • 한국가시화정보학회:학술대회논문집
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    • 2004.11a
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    • pp.60-63
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    • 2004
  • A new PIV technique was developed for decreasing optical error which was created during simultaneous measurements of velocity fields at a wall-normal plane and wall-parallel plane by a plane PIV and a Stereoscopic PIV system. The two Nd:Yag laser systems and three CCD cameras were. synchronized to obtain instantaneous velocity fields at the same time. To avoid optical noise at the crossing line by the two laser light sheets, a new optical arrangement using polarization was applied. The obtained velocity fields show the existence of hairpin packet structure vividly and the idealized hairpin vortex signature is confirmed by experiment.

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An experimental analysis of the fluid flow in an automobile HVAC system using a PIV technique (PIV기법을 이용한 차량용 공조 시스템 내부유동에 대한 실험적 연구)

  • Ji, Ho-Seong;Kim, Bo-Ram;Lee, Sang-Joon
    • 한국가시화정보학회:학술대회논문집
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    • 2007.11a
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    • pp.92-96
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    • 2007
  • Internal flow characteristics for an automobile HVAC have been investigated using a high-resolution PIV technique. The PIV system consists of a 2-head Nd:YAG laser(125 mJ), a high-resolution CCD camera($2K\;{\times}\;2K$), optics and a synchronizer. An automobile HVAC module was used directly. Only the casing was remodeled transparently for capturing flow image and laser sheet beam illumination. Time-averaged velocity field were measured in three temperature control mode. For three temperature control modes, the internal flow characteristics for an automobile HVAC system were evaluated from PIV results..

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Development of range finder using long wavelength laser (장파장 레이저를 이용한 거리 측정기 개발)

  • 유병헌;신보성;장원석;김재구;황경현
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2003.06a
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    • pp.938-941
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    • 2003
  • As the application area of range finder initially developed for military purpose has been extended, the necessity of precision measurement for long distance and its miniaturization is being presented. Recently, LRF(Laser Range Finder) is widely used because it shows more accurate results of range finding. However, most of LRFs use laser source which have wavelength ranges harmful to the human eyes. In this study, we developed the LRF using OPO(Optical Parametric Oscillator) which can stretch laser wavelength to safe region and realized more compact one using solid state laser

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PIV Measurements of the Pressure Driven Flow Inside a T-Shaped Microchannel (T형 마이크로채널 내부 압력구동 유동의 PIV 계측)

  • Choi Jayho;Lee In-Seop
    • Proceedings of the KSME Conference
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    • 2002.08a
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    • pp.423-426
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    • 2002
  • A custom micro-PIV optics assembly has been used to measure the flow field inside a T-shaped microchannel. The micro-PIV system consists of microscope objectives of various magnifications, a dichroic cube, and an 8-bit CCD camera. Fluorescent particles of diameters 620nm have been used with a Nd:YAG laser and color filters. A programmable syringe pump with Teflon tubings were used to inject particle-seeded distilled water into the channel at flow rates of $420,\;40,\;60{\mu}L/hr$. The microchannels are fabricated with PDMS with a silicon mold, then $O_2-ion$ bonded onto a slide glass. Results show differences in flow characteristics and resolution according to fluid injection rates, and magnifications, respectively. The results show PIV results with vector-to-vector distances of $2{\mu}m$ with 32 pixel-square interrogation windows at $50{\%}$ overlap.

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A study on the effect of injection pressure and ambient pressure for the growth of impinging spray (충돌 분무의 성장에 미치는 분사압과 배압의 영향에 관한 연구)

  • Cha, Geon-Jong;Seo, Gyeong-Il;Kim, Deok-Jul
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.11
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    • pp.1458-1465
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    • 1997
  • This study investigated the effects of pressure on the growth of an impinging spray. We obtained the frozen images which were scattered by Nd ; YAG laser light (pulse width : 7 ns) using synchronization circuit made in the laboratory. For an impinging spray a growth of the penetration length was progressed with increase of the injection pressure but an ambient pressure restrained its growth. The effect of an ambient pressure on penetration was larger than that of an injection pressure. The pressure ratio had an effect on the penetration growth rate. The thickness growth rate depended on both the injection pressure and the ambient pressure compositively. A lower injection pressure or a higher ambient pressure was required for spatial distribution of impinging spray.

Time- Dependent FEM Simulation of Dilution Control of Laser Cladding by Adaptive Mesh Method

  • Kim, Jae-Do;Peng, Yun
    • Journal of Mechanical Science and Technology
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    • v.14 no.2
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    • pp.177-187
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    • 2000
  • Dilution is an important factor which influences the properties of clad layer. In this paper the change of dilution during laser cladding and the control of dilution are simulated by a finite element method. The adaptive mesh method is adopted for the time-dependent finite element method computation so that the shape of melt pool can be well represented. The situation of the width control of melt pool is also simulated, which indicates that the dilution can be controlled if the width of melt pool is controlled. Computational results indicate that if a line energy (input energy per unit distance) remains constant the dilution will increase with time, especially at the beginning. Simulation results show that it is possible to control dilution in a certain range if the line energy decreases with time. Experiment of Nd: YAG laser cladding with wire feeding is performed. Experiment results coincide well with the FEM results.

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Property of Multi-Direction Mount Using Magneto-Rheological Fluid (MR유체를 이용한 다방향 제진형 마운트의 응답특성)

  • Ahn, Young-Kong;Sin, Dong-Choon;Yag, Bo-Suk;Kim, Dong-Jo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11a
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    • pp.325.1-325
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    • 2002
  • This paper presents property of the squeeze mode type mount using Magneto-Rheological fluid (MR fluid). The mount can isolate multi-directional vibrations, and also effectively reduce the vibrations in a wide range of disturbance frequency by controling the applied magnetic field. The shape of the mount is the same that of squeeze film damper. In the present work, the performance of this mount was experimentally investigated according to changing the magnetic field strength. (omitted)

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Uniform metal droplet generation using laser (레이저를 이용한 균일 금속 액적 생성)

  • 강대현;양영수;김용욱;조성규;박성민
    • Laser Solutions
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    • v.5 no.1
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    • pp.23-31
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    • 2002
  • The uniform metal droplet generation using Nd-YAG laser was studied and experiment was carried out. The shape and volume of developed droplet was measured and the Young-Laplace equation and equilibrium condition of force were applied this model. The differential equation predicting shape of droplet using equilibrium condition of force instead of Navier-stokes equation was induced and numerical solution of differential equation compared with experimentation data. The differential equation was solved by Runge-Kutta method. Surface tension coefficient of droplet was determined with numerical solution relate to experimental result under the statical condition. In case of dynamic vibration, metal droplet shape and detaching critical volume are predicted by recalculating proposed model. The result revealed that this model could reasonably describe the behavior of molten metal droplet on vibration.

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