• 제목/요약/키워드: Computational Structure Dynamics

검색결과 427건 처리시간 0.024초

난류 경계층 모델을 고려한 AGARD 445.6 날개의 플러터 해석 및 실험결과 비교 (Comparison Study of Viscous Flutter Boundary for the AGARD 445.6 Wing Using Different Turbulent Boundary Layer Models)

  • 김요한;김동현;김동만;김수현
    • 한국군사과학기술학회지
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    • 제12권6호
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    • pp.704-710
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    • 2009
  • In this study, a comparison study of flutter analysis for the AGARD 445.6 wing with wind turnnel test data has been conducted in the subsonic, transonic and supersonic flow regions. Nonlinear aeroelastic using FSIPRO3D which is a generalized user-friendly fluid-structure analyses have been conducted for a 3D wing configuration considering shockwave and turbulent viscosity effects. The developed fluid-structure coupled analysis system is applied for aeroelastic computations combining computational structure dynamics(CSD), finite element method(FEM) and computations fluid dynamics(CFD) in the time domain. MSC/NASTRAN is used for the vibration analysis of a wing model, and then the result is applied to the FSIPRO3D module. the results for dynamic aeroelastic response using different turbulent models are presented for several Mach numbers. Calculated flutter boundary are compared with the wind-tunnel experimental and the results show very good agreements.

Nonlinear fluid-structure interaction of bridge deck: CFD analysis and semi-analytical modeling

  • Grinderslev, Christian;Lubek, Mikkel;Zhang, Zili
    • Wind and Structures
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    • 제27권6호
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    • pp.381-397
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    • 2018
  • Nonlinear behavior in fluid-structure interaction (FSI) of bridge decks becomes increasingly significant for modern bridges with increasing spans, larger flexibility and new aerodynamic deck configurations. Better understanding of the nonlinear aeroelasticity of bridge decks and further development of reduced-order nonlinear models for the aeroelastic forces become necessary. In this paper, the amplitude-dependent and neutral angle dependent nonlinearities of the motion-induced loads are further highlighted by series of computational fluid dynamics (CFD) simulations. An effort has been made to investigate a semi-analytical time-domain model of the nonlinear motion induced loads on the deck, which enables nonlinear time domain simulations of the aeroelastic responses of the bridge deck. First, the computational schemes used here are validated through theoretically well-known cases. Then, static aerodynamic coefficients of the Great Belt East Bridge (GBEB) cross section are evaluated at various angles of attack, leading to the so-called nonlinear backbone curves. Flutter derivatives of the bridge are identified by CFD simulations using forced harmonic motion of the cross-section with various frequencies. By varying the amplitude of the forced motion, it is observed that the identified flutter derivatives are amplitude-dependent, especially for $A^*_2$ and $H^*_2$ parameters. Another nonlinear feature is observed from the change of hysteresis loop (between angle of attack and lift/moment) when the neutral angles of the cross-section are changed. Based on the CFD results, a semi-analytical time-domain model for describing the nonlinear motion-induced loads is proposed and calibrated. This model is based on accounting for the delay effect with respect to the nonlinear backbone curve and is established in the state-space form. Reasonable agreement between the results from the semi-analytical model and CFD demonstrates the potential application of the proposed model for nonlinear aeroelastic analysis of bridge decks.

Design, development and ground testing of hingeless elevons for MAV using piezoelectric composite actuators

  • Dwarakanathan, D.;Ramkumar, R.;Raja, S.;Rao, P. Siva Subba
    • Advances in aircraft and spacecraft science
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    • 제2권3호
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    • pp.303-328
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    • 2015
  • A design methodology is presented to develop the hingeless control surfaces for MAV using adhesively bonded Macro Fiber Composite (MFC) actuators. These actuators have got the capability to deflect the trailing edge surfaces of the wing to attain the required maneuverability, besides achieving the set aerodynamic trim condition. A scheme involving design, analysis, fabrication and testing procedure has been adopted to realize the trailing edge morphing mechanism. The stiffness distribution of the composite MAV wing is tailored such that the induced deflection by piezoelectric actuation is approximately optimized. Through ground testing, the proposed concept has been demonstrated on a typical MAV structure. Electromechanical analysis is performed to evaluate the actuator performance and subsequently aeroelastic and 2D CFD analyses are carried out to see the functional requirements of wing trailing edge surfaces to behave as elevons. Efforts have been made to obtain the performance comparison of conventional control surfaces (elevons) with morphing wing trailing edge surfaces. A significant improvement in lift to drag ratio is noticed with morphed wing configuration in comparison to conventional wing. Further, it has been shown that the morphed wing trailing edge surfaces can be deployed as elevons for aerodynamic trim applications.

Ar이온 충돌에 의한 Au, Pd(001) 표면에서 재증착 효과의 분자동역학 연구 (Molecular dynamics study of redeposition effect by Ar ion bombardments on Au, Pd(001))

  • 김상필;김세진;김도연;정용재;이광렬
    • 한국진공학회지
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    • 제17권2호
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    • pp.81-89
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    • 2008
  • 분자동역학을 이용하여 이온빔 스퍼터링 과정에서 원자의 거동을 연구하였다. Ar이온이 Au와 Pd(001) 표면에 다양한 에너지와 입사각도로 충돌할 때, 표면원자들 중 일부는 공간으로 떨어져 나갔으며, 반응 후 일부 원자들은 초기 표면보다 위쪽에 재증착 되는 현상이 관찰되었다. 재증착 원자의 수율은 스퍼터된 원자보다 Au의 경우 약 5배, Pd의 경우 약 3배 많이 입사 에너지와 입사 각도에 상관없이 발생됨을 확인하였다. 연속된 입사계산을 통해, 스퍼터링 과정에 발생되는 다양한 표면 패턴 형성 메커니즘을 식각만으로 설명하고 있는 종래의 개념과는 달리, 이온빔으로 인해 끊임없이 발생되는 재증착 원자들이 표면의 구조를 형성하는데 중요한 역할을 하는 것으로 확인되었다.

Structure of Particle Clusters Formed in Gas-Solid flows

  • Tanaka, Toshitsugu;Ito, Akihito;Tsuji, Takuya
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2006년도 추계 학술대회논문집
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    • pp.26-27
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    • 2006
  • Characteristics of spatial structure of particle clusters are investigated by using the flow field data obtained from three-dimensional numerical simulations. Eulerian/Lagrangian approach with two-way coupling is applied and individual particle-particle collisions are taken into account by using the hard-sphere model. More than 16 million particles are traced in the maximum case. The results show that the cluster is consisted from the multiple-spatial scale components while the low wave-number, hence the large-scale structure, is dominant. Three-dimensional structure reconstructed from the low-pass filtered data enables us to investigate the essential dynamics of particle clusters in detail.

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PERFORMANCE ANALYSIS OF THE TURBULENCE MODELS FOR A TURBULENT FLOW IN A TRIANGULAR ROD BUNDLE

  • In W.K;Chun T.H;Myong H.K
    • 한국전산유체공학회지
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    • 제10권1호
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    • pp.63-66
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    • 2005
  • A computational fluid dynamics(CFD) analysis has been made for fully developed turbulent flow in a triangular bare rod bundle with a pitch to diameter ratio (P/D) of 1.123. The nonlinear turbulence models predicted the turbulence-driven secondary flow in the triangular subchannel. The nonlinear quadratic κ-ε models by Speziale[1] and Myong-Kasagi[2] predicted turbulence structure in the rod bundle fairly well. The nonlinear quadratic and cubic k-ε models by Shih et al.[3] and Craft et al.[4] showed somewhat weaker anisotropic turbulence. The differential Reynolds stress model by Launder et al.[5} appeared to over predict the turbulence anisotropy in the rod bundle.

격자 변형 기법을 사용한 운동하는 2차원 실린더 주위의 유동 해석 (ANALYSIS OF TWO-DIMENSIONAL FLOW AROUND AN OSCILLATING CYLINDER USING MOVING MESH TECHNIQUES)

  • 이희범;이신형
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2010년 춘계학술대회논문집
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    • pp.542-547
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    • 2010
  • Recently, thanks to advanced computational power and numerical techniques, it is made possible to analyze the flow around moving bodies using computational fluid dynamics techniques. In those simulations, moving mesh techniques should be able to represent both the body motion and boundary deformation which are frequently encounterd in fluid-structure interaction and/of six degree-of-freedom problems. There are several moving mesh techniques such as the Laplacian operator based, tension spring based and elastic deformation based methods. In the present study, the Laplacian operator based method was utilized and the results were validated. For the validation, the flow around an oscillating two-dimensional cylinder was simulated and analyzed.

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Wing Design Optimization for a Long-Endurance UAV using FSI Analysis and the Kriging Method

  • Son, Seok-Ho;Choi, Byung-Lyul;Jin, Won-Jin;Lee, Yung-Gyo;Kim, Cheol-Wan;Choi, Dong-Hoon
    • International Journal of Aeronautical and Space Sciences
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    • 제17권3호
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    • pp.423-431
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    • 2016
  • In this study, wing design optimization for long-endurance unmanned aerial vehicles (UAVs) is investigated. The fluid-structure integration (FSI) analysis is carried out to simulate the aeroelastic characteristics of a high-aspect ratio wing for a long-endurance UAV. High-fidelity computational codes, FLUENT and DIAMOND/IPSAP, are employed for the loose coupling FSI optimization. In addition, this optimization procedure is improved by adopting the design of experiment (DOE) and Kriging model. A design optimization tool, PIAnO, integrates with an in-house codes, CAE simulation and an optimization process for generating the wing geometry/computational mesh, transferring information, and finding the optimum solution. The goal of this optimization is to find the best high-aspect ratio wing shape that generates minimum drag at a cruise condition of $C_L=1.0$. The result shows that the optimal wing shape produced 5.95 % less drag compared to the initial wing shape.

기하학적 보존을 만족하는 최소제곱법을 활용한 무격자 구조해석 기법 개발 (Development of Meshless Method Using Least-Squares Method with Geometric Conservation Law for Structural Dynamic Analysis)

  • 이상우;허진영;김규홍
    • 한국전산구조공학회논문집
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    • 제36권1호
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    • pp.67-74
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    • 2023
  • A meshless technique using the geometric conservation least-squares method (GC-LSM) was devised to discretize the governing equation of linear elasticity. Although the finite-element method is widely used for structural analysis, a meshless method was developed because of its advantages in a moving grid system. This work is the preliminary phase for developing a fully meshless-based fluid-structure interaction solver. In this study, Cauchy's momentum equation was discretized in strong form using GC-LSM for the structural domain, and the Newmark beta method was used for time integration. The solver was validated in 1D, 2D, and 3D benchmarking problems. Static and dynamic results were obtained. The results are more accurate than those of analytic solutions.

Pulsatile Blood Flows Through a Bileaflet Mechanical Heart Valve with Different Approach Methods of Numerical Analysis : Pulsatile Flows with Fixed Leaflets and Interacted with Moving Leaflets

  • Park, Choeng-Ryul;Kim, Chang-Nyung;Kwon, Young-Joo;Lee, Jae-Won
    • Journal of Mechanical Science and Technology
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    • 제17권7호
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    • pp.1073-1082
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    • 2003
  • Many researchers have investigated the blood flow characteristics through bileaflet mechanical heart valves using computational fluid dynamics (CFD) models. Their numerical approach methods can be classified into three types; steady flow analysis, pulsatile flow analysis with fixed leaflets, and pulsatile flow analysis with moving leaflets. The first and second methods have been generally employed for two-dimensional and three-dimensional calculations. The pulsatile flow analysis interacted with moving leaflets has been recently introduced and tried only in two-dimensional analysis because this approach method has difficulty in considering simultaneously two physics of blood flow and leaflet behavior interacted with blood flow. In this publication, numerical calculation for pulsatile flow with moving leaflets using a fluid-structure interaction method has been performed in a three-dimensional geometry. Also, pulsatile flow with fixed leaflets has been analyzed for comparison with the case with moving leaflets. The calculated results using the fluid-structure interaction model have shown good agreements with results visualized by previous experiments. In peak systole. calculations with the two approach methods have predicted similar flow fields. However, the model with fixed leaflets has not been able to predict the flow fields during opening and closing phases. Therefore, the model with moving leaflets is rigorously required for advanced analysis of flow fields.