• Title/Summary/Keyword: Euler Method

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Nonlinear Dynamic Analysis of a Large Deformable Beam Using Absolute Nodal Coordinates

  • Jong-Hwi;Il-Ho;Tae-Won
    • International Journal of Precision Engineering and Manufacturing
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    • v.5 no.4
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    • pp.50-60
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    • 2004
  • A very flexible beam can be used to model various types of continuous mechanical parts such as cables and wires. In this paper, the dynamic properties of a very flexible beam, included in a multibody system, are analyzed using absolute nodal coordinates formulation, which is based on finite element procedures, and the general continuum mechanics theory to represent the elastic forces. In order to consider the dynamic interaction between a continuous large deformable beam and a rigid multibody system, a combined system equations of motion is derived by adopting absolute nodal coordinates and rigid body coordinates. Using the derived system equation, a computation method for the dynamic stress during flexible multibody simulation is presented based on Euler-Bernoulli beam theory, and its reliability is verified by a commercial program NASTRAN. This method is significant in that the structural and multibody dynamics models can be unified into one numerical system. In addition, to analyze a multibody system including a very flexible beam, formulations for the sliding joint between a very deformable beam and a rigid body are derived using a non-generalized coordinate, which has no inertia or forces associated with it. In particular, a very flexible catenary cable on which a multibody system moves along its length is presented as a numerical example.

Flow-Induced Vibration of Transonic Turbine Cascades Considering Viscosity and Shock Wave Effects (점성 및 충격파 효과를 고려한 천음속 터빈 케스케이드의 유체유발 진동해석)

  • Oh, Se-Won;Kim, Dong-Hyun;Park, Oung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2006.05a
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    • pp.793-802
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    • 2006
  • In this study, a fluid/structure coupled analysis system for simulating complex flow-induced vibration (FIV) phenomenon of cascades has been developed. The flow is modeled using Euler and Wavier-Stokes equations with different turbulent models. The fluid domains are modeled using the unstructured grid system with dynamic deformations due to the motion of structural boundary. The Spalart-Allmaras (S-A) and the SST ${\kappa}-{\omega}$ turbulent models are used to predict the transonic turbulent flows. A fully implicit time marching scheme based on the Newmark direct integration method is used in order to solve the coupled governing equations for viscous flow-induced vibration phenomena. For the purpose of validation for the developed FIV analysis system, comparison results for computational analyses of steady and unsteady aerodynamics and flutter analyses are presented in the transonic flow region. In addition, flow-induced vibration analyses for the isolated cascade and multi-blades cascade models have been conducted to show the physical fluid-structure interaction effects in the time domain.

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Vibration Analysis of Cantilever Beams Having a Concentrated Tip Mass and a Crack (끝단 집중질량과 크랙을 가진 외팔보의 진동 해석)

  • Kim, Kyung-Ho;Eom, Seung-Man;Yoo, Hong-Hee
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2006.05a
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    • pp.1360-1365
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    • 2006
  • In this paper the vibration analysis of cantilever beams having a concentrated tip mass and an open crack are performed. The influences of a concentrated tip mass, the crack depth, and the crack position on the natural frequencies of the cracked cantilever beam are investigated by a numerical method. The cracked cantilever beam is modeled based on the Euler-Bernoulli beam theory. The flexibility due to crack is calculated using a fracture mechanics theory. The crack is assumed to be opened during the vibrations. The results obtained by the present method were compared with experimental results to verify the theory. As inspected, as the crack depth and the concentrated tip mass increase, the natural frequencies of the beam decrease. In general, the natural frequencies of the cantilever beam are more sensitive to the depth of the crack than the position of the crack.

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Non-linear Vibration Analysis for the In-plane Motion of a Semi-circular Pipe Conveying Fluid (유체를 수송하는 반원형 곡선관의 면내운동에 대한 비선형 진동 해석)

  • 정두한;정진태
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.05a
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    • pp.677-682
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    • 2003
  • The non-linear dynamic characteristics of a semi-circular pipe conveying fluid are investigated when the pipe is clamped at both ends. To consider the geometric non-linearity for the radial and circumferential displacements, this study adopts the Lagrange strain theory for large deformation and the extensible dynamics based on the Euler-Bernoulli beam theory for slenderness assumption. By using the Hamilton principle, the non-linear partial differential equations are derived for the in-plane motions of the pipe, considering the fluid inertia forces as a kind of non-conservative forces. The linear and non-linear terms in the governing equations are compared with those in the previous study, and some significant differences are discussed. To investigate the dynamic characteristics of the system, the discretized equations of motion are derived form the Galerkin method. The natural frequencies varying with the flow velocity are computed fen the two cases, which one is the linear problem and the other is the linearized problem in the neighborhood of the equilibrium position. Finally, the time responses at various flow velocities are directly computed by using the generalized- method. From these results, we should to describe the non-linear behavior to analyze dynamics of a semi-circular pipe conveying fluid more precisely.

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New Non-linear Modelling for Vibration Analysis of Straight Pipe Conveying Fluid (유체 유동을 갖는 직선관의 진동 해석을 위해 새로운 비선형 모델링)

  • Lee, Soo-Il;Chung, Jin-Tai;Im, Hyung-Bin
    • Proceedings of the KSME Conference
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    • 2001.06b
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    • pp.372-377
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    • 2001
  • A new non-linear of a straight pipe conveying fluid is presented for vibration analysis when the pipe is fixed at both ends. Using the Euler-Bernoulli beam theory and the non-linear Lagrange strain theory, from the extended Hamilton's principle are derived the coupled non-linear equations of motion for the longitudinal and transverse displacements. These equations of motion for are discretized by using the Galerkin method. After the discretized equations are linearized in the neighbourhood of the equilibrium position, the natural frequencies are computed from the linearized equations. On the other hand, the time histories for the displacements are also obtained by applying the $generalized-{\alpha}$ time integration method to the non-linear discretized equations. The validity of the new modeling is provided by comparing results from the proposed non-linear equations with those from the equations proposed by $Pa{\ddot{i}}dousis$.

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The Effect of Partial Closure of the Duct Exit on the Impulsive Wave Impinging upon a Flat Plate (평판에 충돌하는 펄스파에 미치는 관출구 부분폐쇄의 영향)

  • Shin, Hyun-Dong;Lee, Young-Ki;Kim, Heuy-Dong;Setoguchi, Toshiaki
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.1595-1600
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    • 2004
  • When a shock wave arrives at a duct, an impulsive wave is discharged from the duct exit and causes serious noise and vibration problems. In the current study, the characteristics of the impulsive wave discharged from a partial closed duct exit is numerically investigated using a CFD method. The Yee-Roe- Davis's total variation diminishing(TVD) scheme is used to solve the axisymmetric, unsteady, compressible Euler equations. With several partial closed duct exits, the Mach number of the incident shock wave $M_s$ and the distance L/D between the duct exit and a flat plate are varied in the range of $M_s$ = 1.01 ${\sim}$ 1.50 and L/D = 1.0 ${\sim}$ 4.0, respectively. The results obtained show that the magnitude of the impulsive wave impinging upon the flat plate strongly depends upon $M_s$, L/D and the partial closure of duct exit. The impulsive wave on the flat plate can be considerably alleviated by the partial closure of duct exit and, thus, the present method can be a passive control for the impulsive wave.

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Dynamic Modeling and Manipulability Analysis of Underwater Robotic Arms (수중로봇팔의 동역학 모델링과 동적 조작도 해석)

  • Jnn Bong-Huan;Lee Jihong;Lee Pan-Mook
    • Journal of Institute of Control, Robotics and Systems
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    • v.11 no.8
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    • pp.688-695
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    • 2005
  • This paper describes dynamic manipulability analysis of robotic arms moving in viscous fluid. The manipulability is a functionality of manipulator system in a given configuration under the limits of joint ability with respect to the task required to be performed. To investigate the manipulability of underwater robotic arms, a modeling and analysis method is presented. The dynamic equation of motion of underwater manipulator is derived based on the Lagrange-Euler equation considering with the hydrodynamic forces caused by added mass, buoyancy and hydraulic drag. The hydrodynamic drag term in the equation is established as analytical form using Denavit-Hartenberg (D-H) link coordination of manipulator. Two analytical approaches based oil manipulability ellipsoid are presented to visualize the manipulability of robotic arm moving in viscous fluid. The one is scaled ellipsoid which transforms the boundary of joint torque to acceleration boundary of end-effector by normalizing the torques in joint space, while the other is shifted ellipsoid which depicts total acceleration boundary of end-effector by shifting the ellipsoid as much as gravity and velocity dependent forces in work space. An analysis example of 2-link manipulator with proposed analysis scheme is presented to validate the method.

Spray Combustion Simulation in Transverse Injecting Configurations

  • Yi, Yoon-Yong;Roh, Tae-Seong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.03a
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    • pp.186-191
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    • 2004
  • The reactive flowfield of the transverse injecting combustor has been studied using Euler-Lagrange method in order to develop an efficient solution procedure for the understanding of liquid spray combustion in the transverse injecting combustor which has been widely used in ramjets and turbojet afterburners. The unsteady two-dimensional gas-phase equations have been represented in Eulerian coordinates and the liquid-phase equations have been formulated in Lagrangian coordinates. The gas-phase equations based on the conservation of mass, momentum, and energy have been supplemented by combustion. The vaporization model takes into account the transient effects associated with the droplet heating and the liquid-phase internal circulation. The droplet trajectories have been determined by the integration of the Lagrangian equation in the flow field obtained from the separate calculation without considering the iterative effect between liquid and gas phases. The reported droplet trajectories had been found to deviate from the initial conical path toward the flow direction in the very end of its lifetime when the droplet size had become small due to evaporation. The integration scheme has been based on the TEACH algorithm for gas-phase equation, the second order Runge-Kutta method for liquid-phase equations and the linear interpolation between the two coordinate systems. The calculation results has shown that the characteristics of the droplet penetration and recirculation have been strongly influenced by the interaction between gas and liquid phases in such a way that most of the vaporization process has been confined to the wake region of the injector, thereby improving the flame stabilization properties of the flowfield.

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Lifting Analysis for a Sunken Ship in Consideration of Elongation of Crane Ropes (크레인 로프의 신장을 고려한 침몰선체의 인양력 해석)

  • Choi, Kyung-Sik;Shin, Maeng-Kee
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2003.05a
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    • pp.179-184
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    • 2003
  • This study focuses on an analytical approach to calculate crane lifting forces for a sunken ship in consideration oj elongation of crane ropes. The method takes into account the relation of lifting forces acting in wire rope slings to the inclination of the ship's hull including the effect of lug positions. For lifting analysis, the Euler angles are defined to represent the inclination of a sunken ship in developing the static force and moment equations. An additional compatability condition is introduced in order to solve an indeterminate lifting analysis problem with 4 cranes and a set of lifting forces along the 4 crane ropes is calculated. A 3-dimensional example of the G/T 1500 oil tanker is analyzed and the results show that the information obtained by the method could be useful to engineers to conduct salvage work.

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Multi-Point Aerodynamic Design Optimization of DLR F-6 Wing-Body-Nacelle-Pylon Configuration

  • Saitoh, Takashi;Kim, Hyoungjin;Takenaka, Keizo;Nakahashi, Kazuhiro
    • International Journal of Aeronautical and Space Sciences
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    • v.18 no.3
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    • pp.403-413
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    • 2017
  • Dual-point aerodynamic design optimization is conducted for DLR-F6 wing-body-nacelle-pylon configuration adopting an efficient surface mesh movement method for complex junction geometries. A three-dimensional unstructured Euler solver and its discrete adjoint code are utilized for flow and sensitivity analysis, respectively. Considered design conditions are a low-lift condition and a cruise condition in a transonic regime. Design objective is to minimize drag and reduce shock strength at both flow conditions. Shape deformation is made by variation of the section shapes of inboard wing and pylon, nacelle vertical location and nacelle pitch angle. Hicks-Henne shape functions are employed for deformation of the section shapes of wing and pylon. By the design optimization, drag coefficients were remarkably reduced at both design conditions retaining specified lift coefficient and satisfying other constraints. Two-point design results show mixed features of the one-point design results at low-lift condition and cruise conditions.