• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.865-868
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• 2006

In this paper, a dynamic behavior(natural frequency) of a cracked simply supported pipe conveying fluid is presented. In addition, an analysis of the flutter and buckling instability of a cracked pipe conveying fluid due to the coupled mode (modes combined) is presented. Based on the Euler-Bernouli beam theory, the equation of motion can be constructed by using the Lagrange's equation. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments. The stiffness of the spring depends on the crack severity and the geometry of the cracked section. The crack is assumed to be in the first mode of fracture and to be always opened during the vibrations. This study will contribute to the safety test and stability estimation of structures of a cracked pipe conveying fluid.

• Journal of KSNVE
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• v.10 no.2
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• pp.280-290
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• 2000

The paper deals with vibration suppression and dynamic stability of a vertical cantilevered pipe conveying an internal flowing fluid and having an attached mass. Real pipe systems may have some valves or mechanical attached parts, which can be regarded as attached lumped masses. The effect of attached mass on the dynamic stability of a cantilevered pipe conveying fluid is investigated for different locations and magnitudes of the attached mass. The flow rate was controlled through motor pump output and measured by a flow meter. Experimental resutls in the vicinity of flutter fluid velocity were compared with theoretical predictions. It has been found that the experimental results are in substantial agreement with the theoretical predictions. Finally, in order to suppress the vibration of the pipe subjected to a disturbance, and control technique using an internal flowing fluid is introduced.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.5
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• pp.407-412
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• 2012

The dynamic instability and natural frequency of an axially moving pipe conveying fluid are investigated. Thus, the effects of fluid velocity and moving speed on the stability of the system are studied. The governing equation of motion of the moving pipe conveying fluid is derived from the extended Hamilton's principle. The eigenvalues are investigated for the pipe system via the Galerkin method under the simple support boundary. Numerical examples show the effects of the fluid velocity and moving speed on the stability of system. Moreover, the lowest critical moving speeds for the simply supported ends have been presented.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.10
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• pp.976-982
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• 2007

In this paper the vibration system is consisted of a rotating cantilever pipe conveying fluid and tip mass. The equation of motion is derived by using the Lagrange's equation. The system of pipe conveying fluid becomes unstable by flutter. Therefore, the influence of a rotating angular velocity, mass ratio, the velocity of fluid flow and tip mass on the stability of a cantilever pipe by the numerical method are studied. The critical flow velocity for flutter is proportional to the angular velocity and tip mass of the cantilever pipe. Also, the critical flow velocity and stability maps of the pipe system are obtained by changing the mass ratios.

• Journal of Ocean Engineering and Technology
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• v.16 no.6
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• pp.18-24
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• 2002

The vibrational system in this study consists of a cantilever pipe conveying fluid, the moving mass upon it, and an attached tip mass. The equation of motion is derived by using the Lagrange equation. The influences of the velocity and the velocities of fluid flow in the pipe have been studied on the dynamic behavior of a cantilever pipe using a numerical method. While the moving mass moves upon the cantilever pipe, the velocity of fluid flow and the nozzle angle increase; as a result, the tip displacement of the cantilever pipe, conveying fluid, is decreased. After the moving mass passes over the cantilever pipe, the tip displacement of the pipe is influenced by the potential energy of the cantilever pipe and the deflection of the pipe; the effect is the result of the moving mass and gravity. As the velocity of fluid flow and nozzle angle increases, the natural frequency of he system is decreased at the second mode and third mode, but it is increased at the first mode. As the moving mass increases, the natural frequency of the system is decreased at all modes.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.983-986
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• 2005

Free vibration characteristics of a curved pipe conveying fluid is studied when the pipe is clamped at both ends. Using the perturbation method, the non-linear governing equations divided into two parts; the steady state non-linear equilibrium equations and the linearized equations of motion in the neighborhood of the equilibrium position. The natural frequencies are computed from the linearized equations of motion. In this study, the equilibrium positions are determined by two types of equations, i.e., (1) the non-linear equations, and (2) the equations obtained by neglecting the non-linear terms. The natural frequencies obtained from the non-linear equilibrium equations are compared to those obtained from the linearized equilibrium equations. From the results, as the fluid velocity increases, the equilibrium position should be determined from the nonlinear equations for the vibration analysis of the curved pipe conveying fluid.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.11
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• pp.1119-1126
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• 2007

In this paper, the dynamic stability of a cracked cantilever pipe conveying fluid with tip mass is investigated. The pipe is modelled by the Euler-Bernoulli beam theory in which rotatory inertia and shear deformation effects are ignored. The equation of motion is derived by the energy expressions using extended Hamilton's Principle. The crack section is represented by a local flexibility matrix connecting two undamaged pipe segments. The influence of the crack severity, the position of crack, the mass ratio, and a tip mass on the stability of a cantilever pipe conveying fluid are studied by the numerical method. Besides, the critical flow velocity and the stability maps of the pipe system as a function of mass ratios($\beta$) for the changing each parameter are obtained.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.1185-1190
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• 2007

In this paper the vibration system is consisted of a rotating cantilever pipe conveying fluid. The equation of motion is derived by using the Lagrange's equation. Also, the equation of motion is derived applying a modeling method that employs hybrid deformation variables. Generally, the system of pipe conveying fluid becomes unstable by flutter. So, we studied about the influences of the rotating angular velocity, mass ratio and the velocity of fluid flow on the stability of a cantilever pipe by the numerical method. The influences of mass ratio, the velocity of fluid, the angular velocity of a cantilever pipe and the coupling of these factors on the stability of a cantilever pipe are analytically clarified. The critical fluid velocity$(u_{cr})$ is proportional to the angular velocity of the cantilever pipe. In this paper Flutter(instability) always occur in the second mode of the system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.80-85
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• 2002

A conveying fluid cantilever pipe system subjected to an uniformly distributed tangential follower force and three moving masses upon it constitute this vibrational system. The influences of the velocities of moving masses, the distance between two moving masses. and the uniformly distributed tangential follower force have been studied on the dynamic behavior of a cantilever pipe system by numerical mettled. The uniformly distributed tangential follower force is considered within its ciritical value of a cantilever pipe without moving masses, and three constant velocities and three constant distance between two moving masses are also chosen. When the moving masses exist on pipe, As the velocity of the moving mass and distributed tangental force increases, the deflection of cantilever pipe conveying fluid is decreased, respectively. Increasing of the velocity of fluid flow make the amplitude of cantilever pipe conveying fluid decrease. After the moving mass passed upon the pipe, the tip displacement of pipe is influenced by the potential energy of cantilever pipe.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1202-1206
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• 2001

The paper presents the dynamic stability of a vertical cantilevered pipe conveying fluid and having translational linear spring supports. Real pipe systems may have some elastic hanger supports or other mechanical attached parts., which can be regarded as attached spring supports. Governing equations are derived by energy expressions, and numerical technique using Galerkin's method is applied to discretize the equations of small motion of the pipe. Effects of spring supports on the dynamic stability of a vertical cantilevered pipe conveying fluid are fully investigated for various locations and spring constants of elastic supports.