• Title/Summary/Keyword: EOM(Equations of motion)

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Aerodynamic and hydrodynamic force simulation for the dynamics of double-pendulum articulated offshore tower

  • Zaheer, Mohd Moonis;Islam, Nazrul
    • Wind and Structures
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    • v.32 no.4
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    • pp.341-354
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    • 2021
  • Articulated towers are one of the class of compliant offshore structures that freely oscillates with wind and waves, as they are designed to have low natural frequency than ocean waves. The present study deals with the dynamic response of a double-pendulum articulated tower under hydrodynamic and aerodynamic loads. The wind field is simulated by two approaches, namely, single-point and multiple-point. Nonlinearities such as instantaneous tower orientation, variable added mass, fluctuating buoyancy, and geometrical nonlinearities are duly considered in the analysis. Hamilton's principle is used to derive the nonlinear equations of motion (EOM). The EOM is solved in the time domain by using the Wilson-θ method. The maximum, minimum, mean, and standard deviation and salient power spectral density functions (PSDF) of deck displacement, bending moment, and central hinge shear are drawn for high and moderate sea states. The outcome of the analyses shows that tower response under multiple-point wind-field simulation results in lower responses when compared to that of single-point simulation.

Development of an Off-line 6-DOF Simulation Program for Store Separation Analysis (외부 장착물 분리 해석을 위한 Off-line 6-DOF 시뮬레이션 프로그램 개발)

  • Kwak, Ein-Keun;Shin, Jae-Hwa;Lee, Seung-Soo;Choi, Kee-Young;Hyun, Jae-Soo;Kim, Nam-Gyun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.37 no.12
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    • pp.1252-1257
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    • 2009
  • Off-line 6-DOF simulation program for store separation analysis has been developed. The developed program enables to predict a trajectory of a store from the database which was constructed by wind tunnel testing or CFD analysis. The flow angle method was applied to the program for predicting aerodynamic coefficients from the database and the ejector forces and constraints were enabled to incorporate the equations of motion for computing the trajectory. Using the program, the trajectories were calculated and the results are compared with the CTS results.

Dynamic Formulation Using Finite Element and Its Analysis for Flexible Beam (유한요소를 이용한 유연보의 동역학적 정식화 및 해석)

  • Yun Seong-Ho;Eom Ki-Sang
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.18 no.4 s.70
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    • pp.385-393
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    • 2005
  • This paper established the dynamic model of a flexible Timoshenko beam capable of geometrical nonlinearities subject to large overall motions by using the finite element method. Equations of motion are derived by using Hamilton principle and are formulated in terms of finite elements in which the nonlinear constraint equations are adjoined to the system using Lagrange multipliers. The Newmark direct integration method and the Newton-Raphson iteration are employed here for the numerical study which is to demonstrate the efficiency of the proposed formulation.

Real-Time Dynamic Analysis of Vehicle with Experimental Vehicle Model (실험기반 차량모델을 이용한 실시간 차량동역학 해석)

  • Yoo, Wan-Suk;Na, Sang-Do;Kim, Kwang-Suk
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.9
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    • pp.1003-1008
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    • 2012
  • The paper presents an Experimental Vehicle Model (EVM), that utilizes the kinematic characteristics of suspensions from SPMD test data. The relative displacement and orientation of a wheel with respect to the body are represented as a function of the vertical displacement of the wheel. The equations of motion of the vehicle are formulated in terms of local coordinates that do not require coordinate transformation, which improves the efficiency of dynamic analysis. The EOM was modularized for each suspension model, and a $6{\times}6$ vehicle model was obtained by combining six suspensions. The analysis results were compared with ADAMS to verify the accuracy of the EVM. This study also verifies the feasibility of real-time simulation with the developed EVM. For a vehicle simulation for 1 ms, the real simulation time required within 20% of the prescribed time. This result shows that the EVM meets the real-time simulation requirements.