• 제목/요약/키워드: Flow-Structure Interactions

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파랑과 정사각형 배열의 원형 기둥 구조물의 상호작용 수치해석 (Numerical Analysis of Four Circular Columns in Square Array and Wave Interaction)

  • 송성진;박선호
    • 해양환경안전학회지
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    • 제23권5호
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    • pp.558-565
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    • 2017
  • 해양환경의 극한 환경조건에 노출 된 고정식 및 부유식 해양구조물의 안전성과 설계비용 효율성에 있어서 파랑-구조물 상호작용의 정확한 예측은 중요하다. 본 연구에서는 규칙파 중 원형 기둥에 대한 파랑-구조물 상호작용을 해석하였다. 3차원 이상유동(two-phase flow)을 해석하기 위해 오픈소스 전산유체역학 라이브러리인 오픈폼을 사용하였다. 4개의 원형기둥이 정사각형 배열을 이루고 있을 때 규칙파의 입사각도에 따른 상호작용을 해석하였다. 원형 기둥 구조물에서의 wave run-up을 입사파의 기울기에 따라 비교하였다. 원형 기둥과 입사파의 상호작용으로 인해 원형 기둥 사이에 높은 파가 생성되는 것을 확인하였다. 본 해석 결과는 구조물과 입사파의 상호작용에 의한 air gap에 대한 연구의 기초자료로 활용될 것으로 기대된다.

피에조 잉크젯 헤드의 음향파 거동의 수치 해석 (Numerical Simulation of Hydro-Acoustic Flow in Piezo Inkjet Print Head)

  • 이유섭;위상권;오세영;정재우
    • 대한기계학회논문집B
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    • 제31권1호
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    • pp.51-61
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    • 2007
  • This paper presents numerical and theoretical studies of acoustic wave interactions in slightly compressible liquids within piezoelectrically driven inkjet print heads. The interconnected flow channels may cause jet crosstalk, resulting in poor printing quality. It should be reduced by modifying the channel structure with the acoustic wave interactions considered. Compressible gas flow driven by the sudden movement of a top wall in the channel is calculated using Flow3D and is validated with the narrow gap theory. Limited compressibility model of the Flow3D is employed to calculate pressure waves of slightly compressible ink flow. It is found that reducing restrictor width can damp out the jet crosstalk by inhibiting the pressure wave propagation. The degree of crosstalk has been quantified using the maximum values of cross-correlations between neighboring channels and a critical channel dimension for acceptable crosstalk has been proposed. This finding is verified by drop visualization experiments using silicon-micromachined piezo inkjet print heads that are fabricated by our group.

점성 수치파랑수조 기술을 이용한 평판간 난류유동의 LES 해석 (Large-Eddy Simulation of Turbulent Channel Flow Using a Viscous Numerical Wave Tank Simulation Technique)

  • 박종천;강대환;윤현식;전호환
    • 한국해양공학회지
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    • 제18권2호
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    • pp.1-9
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    • 2004
  • As the first step to investigate the nonlinear interactions between turbulence and marine structures inside a viscous NWT, a LES technique was applied to solve the turbulent channel flow for =150. The employed turbulence models included 4 types: the Smagorinsky model, the Dynamic SGS model, the Structure Function model, and the Generalized Normal Stress model. The simulated data in time-series for the LESs were averaged in both time and space, and statistical analyses were performed. The results of the LESs were compared with those of a DNS, developed in the present study and two spectral methods by Yoon et al.(2003) and Kim et a1.(1987). Based on this research, the accuracy of LESs has been found to be still related to the number of grids for fine grid size).

Numerical Study of Flow Characteristics due to Interaction Between a Pair of Vortices in a Turbulent Boundary Layer

  • Yang, Jang-Sik
    • Journal of Mechanical Science and Technology
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    • 제20권1호
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    • pp.147-157
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    • 2006
  • This paper represents a numerical study of the flow field due to the interactions between a pair of vortices produced by vortex generators in a rectangular channel flow. In order to analyze longitudinal vortices induced by the vortex generators, the pseudo-compressibility method is introduced into the Reynolds-averaged Navier-Strokes equations of a 3-dimensional unsteady, incompressible viscous flow. A two-layer $k-{\epsilon}$ turbulence model is applied to a flat plate 3-dimensional turbulence boundary to predict the flow structure and turbulence characteristics of the vortices. The computational results predict accurately the vortex characteristics related to the flow field, the Reynolds shear stresses and turbulent kinetic energy. Also, in the prediction of skin friction characteristics the computational results are reasonably close to those of the experiment obtained from other researchers.

A preliminary simulation for the development of an implantable pulsatile blood pump

  • Di Paolo, Jose;Insfran, Jordan F.;Fries, Exequiel R.;Campana, Diego M.;Berli, Marcelo E.;Ubal, Sebastian
    • Advances in biomechanics and applications
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    • 제1권2호
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    • pp.127-141
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    • 2014
  • A preliminary study of a new pulsatile pump that will work to a frequency greater than 1 Hz, is presented. The fluid-structure interaction between a Newtonian blood flow and a piston drive that moves with periodic speed is simulated. The mechanism is of double effect and has four valves, two at the input flow and two at the output flow; the valves are simulated with specified velocity of closing and reopening. The simulation is made with finite elements software named COMSOL Multiphysics 3.3 to resolve the flow in a preliminary planar configuration. The geometry is 2D to determine areas of high speeds and high shear stresses that can cause hemolysis and platelet aggregation. The opening and closing valves are modelled by solid structure interacting with flow, the rhythmic opening and closing are synchronized with the piston harmonic movement. The boundary conditions at the input and output areas are only normal traction with reference pressure. On the other hand, the fluid structure interactions are manifested due to the non-slip boundary conditions over the piston moving surfaces, moving valve contours and fix pump walls. The non-physiologic frequency pulsatile pump, from the viewpoint of fluid flow analysis, is predicted feasible and with characteristic of low hemolysis and low thrombogenesis, because the stress tension and resident time are smaller than the limit and the vortices are destroyed for the periodic flow.

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.

FIV 시험루프의 유동기인 진동 신호분석 (Flow-Induced Vibration Signal Analysis of the FIV Test Loop)

  • 이강희;강흥석;윤경호;송기남
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2004년도 추계학술대회
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    • pp.601-606
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    • 2004
  • Vibration spectrums of the test loop according to flow conditions were analyzed in order to identify the sources of vibration at peak frequencies. While a flow condition of the sweep test was changed by varying pump rotational speed from 450 rpm to 1500 rpm by the step 150 rpm, midspan acceleration of the test section in width-direction and dynamic pressure perturbation in the test section were measured. Other sources of vibration due to the flow structure interactions, such as acoustic resonance, blade pulsing frequency and bellows wrinkles, were investigated. Pressure perturbation in the section and acoustic resonance due to branch pipe give major effects to the vibration of the test section in high frequency range of 1.5 kHz to 2.8 kHz.

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직교배열표를 이용한 불연속 공간에서의 교호작용을 고려한 구조물 설계 (Design of Structure Using Orthogonal Array Considering Interactions in Discrete Design Spaces)

  • 황광현;권우성;이권희;박경진
    • 대한기계학회논문집A
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    • 제24권12호
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    • pp.2952-2962
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    • 2000
  • The design of experiment(DOE) is getting more attention in the engineering community since it is easy to understand and apply. Recently, engineering designers are adopting DOE with orthogonal arrays when they want to design products in a discrete design space. In this research, a design flow with orthogonal arrays is defined for structural design according to the general DOE. The design problem is defined as a general structural optimization problem. Sensitivity information is evaluated by the analysis of variance(ANOVA), and an optimum design is determined from analysis of means(ANOM). Interactions between design variables are investigated to achieve additivity which should be valid in DOE. When strong interactions exit, a method is proposed. Some methods to consider the problem are suggested.

광 디스크 드라이브의 공력소음 감소에 관한 연구 (A Study on Reduction of Sound Noise Induced by Disk Rotation in Optical Disk Drives)

  • 송인상;박건순;최학현;김수경;이승엽
    • 소음진동
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    • 제9권4호
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    • pp.693-702
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    • 1999
  • We study the characteristics of airflow and sound noise induced by disk rotation in optical disk drives. The characteristics of airflow around a rotating disk surrounded by various tray structures are numerically investigated using a commercial CFD program and then compared with experimental results. Sound pressure and intensity caused by the fluid-structure interactions in the CD/DVD-ROM drive are measured, and the effect of the ariflow on the sound noise and disk vibration is discussed. In order to reduce airflow-induced noise and vibration around the rotating disk, tray geometry is modified. Both numerical and experimental studies implemented with different tray models show that the improved tray model alters the characteristics of the disk-induced airflow, causing the reduction of the airflow-induced sound level.

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화염배출 출구면적 변화에 대한 수직발사관 내부 초음속 충돌유동의 수치적 해석 (NUMERICAL INVESTIGATIONS OF SUPERSONIC JET IMPINGEMENT ON A FLAT WALL IN A CONFINED PLENUM)

  • 이광섭;홍승규;안창수
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2005년도 추계 학술대회논문집
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    • pp.281-285
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    • 2005
  • Viscous solutions of supersonic jet impinging on a flat wall in a confined plenum are simulated using three-dimensional Navier-Stokes solver. A confined plenum was designed for simulating the missile launch and analyzing the behavior of the exhaust plume, which were accompanied by complex flow interactions with shock and boundary layer. Concerns of this paper are to show accurate simulation of internal flow in confined plenum and to demonstrate the jet flow structure when the jet interacts with a small opening on the side. Objectives of this numerical simulation are to understand the effect of changing the plume exit area of the plenum. Pressure and temperature rise at certain position in the plenum are traced and compared with test data.

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