• Title, Summary, Keyword: 유체점성

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Vibration Control of Hybrid Smart Structure Using ER Fluids and Piezoelectric Ceramics (전기점성유체와 압전세라믹을 이용한 복합지능구조물의 진동제어)

  • 윤신일;박근효;한상보
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.13 no.8
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    • pp.612-618
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    • 2003
  • A hybrid vibration control scheme using ER fluid and PZT patches is proposed. Dynamic characteristics of the beam embedded with the ER fluid can be controled by changing the strength of the electric field applied on the ER fluid, thus provides a mean to avoid the resonance. It was found that active vibration control of the structure embedded with ER fluid failed to suppress the vibration excited with broad band frequency due to the limited change of the dynamic characteristics of the structure. To compensate this limited effect of the control scheme with ER fluid alone, PPF control using PZT patches as sensors and actuators is added to construct a hybrid controller. Experimental results suggests that proposed hybrid controller is effective to suppress the additional resonance vibration that appears when each controller is used alone.

Hypersonic flow calculations using AUSMPW+ and Shock-Aligned Grid Technique (AUSMPW+ 수치기법과 충격파 정렬 격자 기법을 이용한 극초음속 유동장 해석)

  • Kim K. H.;Kim C.;Rho O. H.
    • 한국전산유체공학회:학술대회논문집
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    • pp.73-78
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    • 1999
  • 극초음속 유동장의 정확한 해석을 위해 AUSMPW+ 수치기법과 충격파 포착시 생기는 수치오차를 제거하기 위해 충격파 정렬 기법(Shock-Aligned Grid Technique)을 개발하였다. AUSMPW+ 수치기법은 자체 수치점성이 적은 수치기법으로 점성 경계층 계산시 정확한 계산결과를 보여주며 기존의 AUSM 계열이 가지는 문제점인 물성치의 진동 현상을 제거한 수치기법이다. 원통형과 무딘 물체 주위의 극초음속 유동장 해석을 통해 공력이 진동현상 없이 정확하게 계산됨을 확인하였다. 그리고 충격파 정렬 기법의 특성을 파악하기 위해 충격파 반사문제와 충격파-충격파 상호작용 문제를 해석하여 수치오차 없이 충격파를 포착할 수 있음을 보였다. 또한 화학적 평형 비평형 유동 영역까지 충격파 정렬 격자 기법을 확장하였다.

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Numerical study of Three-Dimensional Viscous Flow and Compression Wave Induced by the High Speed Train Entering into a Tunnel (터널에 진입하는 고속전철 주위의 3차원 점성유동과 압축파 특성에 관한 수치해석적 연구)

  • Shin C. H.;Park W. G.
    • Journal of computational fluids engineering
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    • v.5 no.3
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    • pp.23-31
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    • 2000
  • The three-dimensional unsteady compressible Full Navier-Stokes equation solver with sliding multi-block method has been applied to analyze three dimensional characteristics of the viscous flow field and compression wave around the high speed train which is entering into a tunnel. The numerical scheme of AF + ADI was used to efficiently solve Navier-Stokes equations in the curvilinear coordinate system. The vortex formation owing to the viscous interaction around the train was found and the generation of compression wave due to the blockage effects was observed ahead of the train in the form of plane wave. The three dimensional characteristics of the flow field compared to the analytic results were discussed in detail. The variation of pressure of tunnel wall surface and velocity profile of the train are identified as the train enters into a tunnel. The changes in aerodynamic forces and streamlines of each specific sections are also discussed.

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비압축성 점성유체의 유한요소 해석

  • 유원진
    • Computational Structural Engineering
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    • v.11 no.1
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    • pp.90-95
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    • 1998
  • 본 고에서는 비압축성 점성유체의 유한요소해석 기법을 소개하였다. 대류항의 상류화 기법으로 안정된 해를 도출할 수 있으며 Penalty 방법에 기반하여 압력항을 지배방정식으로부터 소거함으로써 해석시간과 요구저장공간을 감소시켰다. 실린더 주변의 유동장을 해석하여 와의 방출을 성공적으로 묘사하였으며 항력계수를 17%정도의 오차로 계산하였다. 적응적 요소세분화 기법에 대한 연구를 통해 적절한 오차평가 기법 및 최적의 체눈을 형성하는 기법을 제시하였다. 또한 동적 해석에 적합한 요소재결합 알고리즘에 대한 연구가 진행중이다. 본 고의 결과는 직접적으로 풍공학분야에 사용하기에는 아직 계산 시간의 효율성이나 해의 정확도 및 안정성면에서 무리가 있으나 추가적인 연구를 통하여 해석기법의 개선을 도모하고 컴퓨터 등 계산장비의 급속한 발전으로 장래에 경쟁력을 획득할 수 있을 것으로 기대된다.

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A New Pressure-Based PISO-Finite Element Method for Navier-Stokes Equations in All Speed Range (Navier-Stokes 점성유동의 전속도 영역 해석을 위한 새로운 압력기반 PISO-유한요소법)

  • Shim E. B.;Chang K. S.
    • Journal of computational fluids engineering
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    • v.1 no.1
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    • pp.112-122
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    • 1996
  • A finite element scheme using the concept of PISO method has been developed to solve the Navier-Stokes viscous flows in all speed range. This scheme includes development of new pressure equation that retains both the hyperbolic term related with the density variation and the elliptic term reflecting the incompressibility constraint. The present method is applied to the incompressible two-dimensional driven cavity flow problems(Re=100, 400 and 1,000). For compressible flows, the Carter plate problem(M=3 and Re=1,000) is computed. Finally, we have simulated the shock-boundary layer interaction(M=2 and Re=2.96×10/sup 5/), a more difficult problem, and compared its results with the experiment to demonstrate the shock capturing capability of the present solution algorithm.

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DEVELOPMENT OF AN UNSTRUCTURED OVERSET MESH METHOD FOR 2-D UNSTEADY VISCOUS FLOW SIMULATION WITH RELATIVE MOTION (상대운동이 있는 이차원 비정상 점성 유동 해석을 위한 비정렬 중첩격자기법 개발)

  • Jung Mun-Seung;Kwon Oh-Joon
    • Journal of computational fluids engineering
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    • v.11 no.2
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    • pp.1-7
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    • 2006
  • An unstructured overset mesh method has been developed for the simulation of unsteady viscous flow fields around multiple bodies in relative motion. For this purpose, a robust and fast search technique is proposed for both triangle and high-aspect ratio quadrilateral cell elements. The interpolation boundary is defined for data communication between grid systems and an interpolation method is suggested for viscous and inviscid cell elements. This method has been applied to calculate the flow fields around 2-D airfoils involving relative motion. Validations were made by comparing the predicted results with those of experiments or other numerical results. It was demonstrated that the present method is efficient and robust for the prediction of unsteady time-accurate flow fields involving multiple bodies in relative motion.

Comparison of Performances refer to Magnetic and Fluid Analysis of Magneto-Rheological Flow Damper (자기점성유체 댐퍼의 자기장 및 유동 해석에 따른 성능비교)

  • Song, Jun-Han;Son, Sung-Wan;Lee, Gyu-Seop;Chun, Chong-Keun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.98-102
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    • 2009
  • The magneto-rheological fluid expresses different cohesiveness according to the strength of the external electric current. To manufacture the magneto-rheological fluid damper that uses such characteristics of the fluid, a flow analysis of the inner damper was conducted to forecast the damper's capacity. In addition, using the finite element method software, analysis on the characteristics of electromagnetic field around the coil operation unit inside the damper. Based on the result of the analysis, a single core damper and a double core damper were built and tested for their dynamic function. Based on the result of the experiment, the propriety of the flow analysis was demonstrated, and the proposed model was verified.

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A Study on the Sensitivity of Computational Parameters in SPH Simulation of Breaking Waves (붕괴파의 SPH 모의 인자의 민감도에 대한 연구)

  • Ha, Sung-Won;Lee, Nam-Joo;Yu, Kwon-Kyu
    • Proceedings of the Korea Water Resources Association Conference
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    • pp.163-163
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    • 2011
  • 평활입자동역학법(SPH, Smoothed Particle Hydrodynamics)은 붕괴파(도수, 댐붕괴류, 쇄파) 등과 같이 수면 변동이 큰 유체 역학 문제를 해결하기 위한 무격자법 중의 하나이다. SPH를 이용한 붕괴파의 모의에서는 압력, 점성, 밀도(압축성), 척력 등 다양한 계산 인자가 필요하다. 이들 인자가 SPH 모의 결과에 미치는 영향을 도수와 댐붕괴류에 대해서 검토하였다. 그 결과 압력과 관련하여, 상태 방정식 계수로 표현되는 유체의 음속은 입자들의 흩어짐 현상과 밀접한 관계를 가지는 것을 밝혀내었다. 평활 거리는 수치해의 안정성과 밀접한 관련이 있으며, 너무 작거나 크게 설정하는 경우 해의 정확도가 떨어지는 것으로 나타났다. 일반적으로 2차원 문제의 경우 20~23개 정도의 입자가 해의 내삽에 사용되는 것이 바람직하다.

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A STUDY OF INCOMPRESSIBLE VISCOUS FLOW ANALYSIS BY VORTEX-IN-CELL METHOD (보오텍스 인 셀 방법을 이용한 점성유동해석 연구)

  • Lee, J.H.;Kim, Y.C.;Lee, K.J.;Suh, J.C.
    • 한국전산유체공학회:학술대회논문집
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    • pp.78-85
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    • 2011
  • The Vortex-In-Cell(VIC) method combined with panel method is applied to the analysis of incompressible unsteady viscous flow. The dynamics of resulting flow is governed by the vorticity transport equation in Lagrangian form with vortex particle representation of the flow field. A regular grid which is independent to the shape of a body is used for numerical evaluation based on immersed boundary technique. With an introduction of this approach, the development and validation of the VIC method is presented with some computational results for incompressible viscous flow around two or three dimensional bodies such as wing section, sphere, finite wing and marine propeller.

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VISCOUS FLOW ANALYSIS OF UNDERWATER PROPULSOR USING AN UNSTRUCTURED OVERSET MESH TECHNIQUE (비정렬 중첩격자기법을 이용한 수중추진기 주위의 점성유동 해석)

  • An, S.J.;Kwon, O.J.;Jung, Y.P.
    • 한국전산유체공학회:학술대회논문집
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    • pp.341-346
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    • 2010
  • In this paper, viscous flow calculation of pump-jet that is used as underwater propulsor was made by using RANS equation. For the validation, calculation for DTRC4119 marine propeller was made and reasonable agreements were obtained between the present results and the experiment. An unstructured overset mesh technique is used for analysis of relative motion between rotor and stator in pump-jet propulsor. Results for pump-jet propulsor were compared with computational results of another researcher.

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