• 제목/요약/키워드: Immersed Boundary

검색결과 186건 처리시간 0.03초

유체에 담긴 기둥의 자유진동 (Free Vibrations of Columns Immersed in Fluid)

  • 오상진;이병구;모정만
    • 한국농공학회:학술대회논문집
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    • 한국농공학회 1999년도 Proceedings of the 1999 Annual Conference The Korean Society of Agricutural Engineers
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    • pp.225-230
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    • 1999
  • The purpose of this paper is to investigate the natural frequencies and mode shape of columns immersed in fluid. The beam model is based on the classical Bernoulli-Euler beam theory which neglects the effects of rotatory inertial and shear deformation. The eccentricity and rotatory inerital of the tip mass are taken into account . The governing differential equations forr the free vibrations of immersed columns are solved numerically using the corresponding boundary conditoins. The lowest four natural frequencies and corresponding mode shapes are calculated over a range of non-dimensional system parameters : the ratio of fluid depth to span length, the mass ratio, the dimensionless mass moment of inertial, and the eccentricity.

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A REGULARIZED CORRECTION METHOD FOR ELLIPTIC PROBLEMS WITH A SINGULAR FORCE

  • Kim, Hyea-Hyun
    • 대한수학회지
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    • 제49권5호
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    • pp.927-945
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    • 2012
  • An approximation of singular source terms in elliptic problems is developed and analyzed. Under certain assumptions on the curve where the singular source is defined, the second order convergence in the maximum norm can be proved. Numerical results present its better performance compared to previously developed regularization techniques.

3차원 부유체의 유체-물체 연성해석 (FLUID-BODY INTERACTION ANALYSIS OF FLOATING BODY IN THREE DIMENSIONS)

  • 고광수;안형택
    • 한국전산유체공학회지
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    • 제20권2호
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    • pp.103-108
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    • 2015
  • Fluid-body interaction analysis of floating body with six degree-of-freedom motion is presented. In this study, three-dimensional incompressible Navier-Stokes equations are employed as a governing equation. The numerical method is based on a finite-volume approach on a cartesian grid together with a fractional-step method. To represent the body motion, the immersed boundary method for direct forcing is employed. In order to simulate the coupled six degree-of-freedom motion, Euler's equations based on rigid body dynamics are utilized. To represent the complex body shape, level-set based algorithm is utilized. In order to describe the free surface motion, the volume of fluid method utilizing the tangent of hyperbola for interface capturing scheme is employed. This study showed three different continuums(air, water and body) are simultaneously simulated by newly developed code. To demonstrate the applicability of the current approach, two different problems(dam-breaking with stationary obstacle and water entry) are simulated and all results are validated.

홈이 있는 원형 실린더를 지나는 유동의 불안정성 (Flow instability in Flow Past O-grooved Circular Cylinder)

  • 김재희;양경수
    • 대한기계학회논문집B
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    • 제39권4호
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    • pp.325-333
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    • 2015
  • 본 연구에서는 층류 점성유동에서 원형 실린더를 기준으로 홈을 이용한 실린더의 형상변화가 유동 특성에 미치는 영향 분석을 2차원 수치 해석으로 수행하였다. 사용한 좌표계는 직교 좌표계로서 가상경계법과 표시 입자 기법을 사용하여 실린더를 구현하였다. 홈의 개수와 위치를 변수로 Re=40, 50에서 계산하였으며, 홈의 수와 위치에 의한 유동 불안정성을 해석하여 임계 레이놀즈 수를 구하였다.

양력형 디스크 풍력 발전기의 유동 및 소음 해석 (Noise and flow analysis of lift-type disk wind power System)

  • 고승철;나지성;이준상
    • 한국가시화정보학회지
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    • 제15권3호
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    • pp.52-56
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    • 2017
  • In this study, we investigate the flow characteristics of lift-type disk which behaves the up-down motion using the large eddy simulation (LES) and immersed boundary method (IBM). Also, we perform the noise analysis using pressure field at 1.35 m distance and reveal the cause of noise to observe the vortical structure analysis of flow result. It is observed that vortical structure and wind shear were generated at leading edge and tower with high velocity deficit and flow separation. High magnitude of flow noise was observed in low frequency range which is from 30 Hz to 60 Hz. It was observed that vortical structure at leading edge was generated in frequency range from 33.3 Hz to 41.6 Hz. Temporal characteristic in vortical structure at leading edge was similar to noise characteristics, having the similar frequency ranges.

원형단면 실린더를 지나는 유동에 대한 자유류 난류강도의 영향 (Effects of Freestream Turbulence Intensity on the Flow Past a Circular Cylinder)

  • 황종연;양경수;이승수;이준식;이상산
    • 대한기계학회논문집B
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    • 제28권8호
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    • pp.953-960
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    • 2004
  • In this study, the effects of freestream turbulence intensity on laminar-turbulent transition of separated shear layers in the wake of a circular cylinder are investigated using an immersed boundary method and LES. It is shown that the present numerical results without freestream turbulence for Re=3,900 based on bulk mean velocity and the cylinder diameter are in good agreement with other authors' experimental observations and numerical results, verifying our numerical methodology. Then a 'prescribed power spectrum' method is imposed to generate isotropic turbulence at the inlet of the computational domain at each time step. The principal effects of freestream turbulence intensity on flow statistics are investigated for Re=3,900. Statistical study reveals that the Reynolds stresses in the near-wake region gradually increase, and transition occurs further upstream, as the turbulence intensity increases. On the other hand, the bubble size behind the cylinder decreases as the turbulence intensity increases, which indicates that the freestream turbulence helps mean velocity be quickly recovered.

자유 낙하하는 사각 실린더 주위의 유동 구조 (Flow Structures Around a Freely-falling, Rectangular Cylinder)

  • 전충호;이창열;윤현식
    • 한국해양공학회지
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    • 제24권5호
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    • pp.8-15
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    • 2010
  • The flow around a two-dimensional, rectangular cylinder that is freely falling in a channel was simulated using the immersed boundary method with direct forcing to determine the interactions between the fluid and the structure. The results of the present study were in good agreement with previous experimental results. Regardless of the H/L ratio (where H and L are the height and width of the rectangular cylinder, respectively), the flow structures had essentially the same pattern as the two symmetrical circulations that form about the horizontal center of the cylinder, with those centers located at each lateral position near the wake. When the cylinder approaches very close to the bottom, a jet-like flow appeared between the bottom of the rectangular cylinder and the channel. When the jet-like flow goes through the channel, surrounding fluids are sucked into this jet, forming the secondary vortices.

이상 유동에서의 유체-구조 연성해석을 위한 Direct Forcing/Ficititious Domain-Level Set Method (Direct forcing/fictitious domain-Level set method for two-phase flow-structure interaction)

  • 전충호;윤현식;정재환
    • 한국해양공학회지
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    • 제25권4호
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    • pp.36-41
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    • 2011
  • In the present paper, a direct forcing/fictitious domain (DF/FD) level set method is proposed to simulate the FSI (fluid-solid interaction) in two-phase flow. The main idea is to combine the direct-forcing/fictitious domain (DF/FD) method with the level set method in the Cartesian coordinates. The DF/FD method is a non-Lagrange-multiplier version of a distributed Lagrange multiplier/fictitious domain (DLM/FD) method. This method does not sacrifice the accuracy and robustness by employing a discrete ${\delta}$ (Dirac delta) function to transfer quantities between the Eulerian nodes and Lagrangian points explicitly as the immersed boundary method. The advantages of this approach are the simple concept, easy implementation, and utilization of the original governing equation without modification. Simulations of various water-entry problems have been conducted to validate the capability and accuracy of the present method in solving the FSI in two-phase flow. Consequently, the present results are found to be in good agreement with those of previous studies.

비대칭 장력 모델을 이용한 예인 물체의 유체-구조 상호작용 모사 (SIMULATION OF FLUID-STRUCTURE INTERACTION OF A TOWED BODY USING AN ASYMMETRIC TENSION MODEL)

  • 신상묵
    • 한국전산유체공학회지
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    • 제16권1호
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    • pp.7-13
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    • 2011
  • The fluid-structure interaction of a towed body is simulated using a developed code, which is based on the flux-difference splitting scheme on the hybrid Cartesian/immersed boundary method. To improve the stability in the coupling between the fluid and structure domains, a scheme is used, in which the effects of structure deformation are treated implicitly. The developed code is validated for the fluid-structure interaction problem through comparisons with other results on the vortex-induced vibration of elastically mounted cylinders. To simulate behavior of a towed body, an asymmetric tension modelling for a towing cable is suggested. In the suggested model, the tension is proportional to the elongation of the cable, but the cable has no effect on the body motion whenever the distance between the endpoints of the cable is smaller than the original length of the cable. The fluid-structure interactions of a towed body are simulated on the basis of different parameters of the towing cables. It is observed that the suggested tension model predicts the snapping for a shorter towing cable, which is in accordance with the reported results.