• 제목/요약/키워드: Homogeneous isotropic turbulence

검색결과 13건 처리시간 0.017초

고속 직접분사식 디젤엔진의 실린더내 유동특성에 관한 실험적 연구 (An Experimental Study of In-Cylindeer Flow Characteristics of a High Speed Direct Injection Diesel Engine)

  • 정경석
    • 한국자동차공학회논문집
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    • 제4권3호
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    • pp.22-30
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    • 1996
  • In-cylinder flow of a purpose-built small HSDI Hydra Diesel engine was investigated by laser Doppler velocimetry(LDV) during induction and compression processes. The flow was quantified in terms of ensemble-averaged axial and swirl velocities, normalized by the mean piston speed, at a plane located 12mm from the cylinder head and corresponding to the mid-plane of the diametrically-opposed quartz windows at an enigne speed of 1000rpm. The formation of toroidal vortices during the intake process and the evolution and decay of swirl motion during the compression process were observed. Turbulence at around TDC of compression became homogeneous and isotropic.

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공간 필터를 이용한 PIV 속도장의 잡음 제거 및 와류 식별 개선 (Denoising PIV velocity fields and improving vortex identification using spatial filters)

  • 정현균;이훈상;황원태
    • 한국가시화정보학회지
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    • 제17권2호
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    • pp.48-57
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    • 2019
  • A straightforward strategy for particle image velocimetry (PIV) interrogation and post-processing has been proposed, aiming at reducing errors and clarifying vortex structures. The interrogation window size should be kept small to reduce bias error and improve spatial resolution. A spatial filter is then applied to the velocity field to reduce random error and clarify flow structure. The performance of three popular spatial filters were assessed: box filter, median filter, and local quadratic polynomial regression filter. In order to quantify random uncertainty, the image matching (IM) method is applied to an experimental dataset of homogeneous and isotropic turbulence (HIT) obtained by 2D-PIV. We statistically analyze the uncertainty propagation through the spatial filters, and verify the reduction in random uncertainty. Moreover, we illustrate that the spatial filters help clarify vortex structures using vortex identification criteria. As a result, PIV random uncertainty was reduced and the vortex structures became clearer by spatial filtering.

PIV 기법을 이용한 캐비테이션 터널에서의 Honeycomb 난류 계측 (Measurement of Honeycomb Turbulence in a Cavitation Tunnel Using Particle Image Velocimetry Method)

  • 류민철;오정근;김유철;고원규;이윤모;서정천
    • 대한조선학회논문집
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    • 제45권1호
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    • pp.42-53
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    • 2008
  • The two dimensional PIV (particle image velocimetry) measurement technique is applied to water flow in a narrow cavitation tunnel. The nearly homogeneous and isotropic turbulent flows are generated by the honeycomb installed in the tunnel and visualized with a PIV technique. The velocities in the measurement plane at the tunnel centerline 184cm downward from the honeycomb were measured and calculated by an image correlation technique. The turbulent properties are evaluated and each term in the turbulent kinetic energy equation is calculated for the conditions with different internal pressures. Lowering the internal pressure gives an effect on the turbulent flow due to growing bubbles which are resolved in the water. The turbulent kinetic energy in the measurement plane is decayed much slower than those of other research results carried out with wind tunnels. With decreasing the tunnel internal pressures the turbulent intensities are increased about 1.5 times and the anisotropic tendency is also increased.