• Structural Engineering and Mechanics
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• v.62 no.1
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• pp.65-77
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• 2017

The free vibration analysis of fluid conveying Timoshenko pipeline with different boundary conditions using Differential Transform Method (DTM) and Adomian Decomposition Method (ADM) has not been investigated by any of the studies in open literature so far. Natural frequencies, modes and critical fluid velocity of the pipelines on different supports are analyzed based on Timoshenko model by using DTM and ADM in this study. At first, the governing differential equations of motion of fluid conveying Timoshenko pipeline in free vibration are derived. Parameter for the nondimensionalized multiplication factor for the fluid velocity is incorporated into the equations of motion in order to investigate its effects on the natural frequencies. For solution, the terms are found directly from the analytical solution of the differential equation that describes the deformations of the cross-section according to Timoshenko beam theory. After the analytical solution, the efficient and easy mathematical techniques called DTM and ADM are used to solve the governing differential equations of the motion, respectively. The calculated natural frequencies of fluid conveying Timoshenko pipelines with various combinations of boundary conditions using DTM and ADM are tabulated in several tables and figures and are compared with the results of Analytical Method (ANM) where a very good agreement is observed. Finally, the critical fluid velocities are calculated for different boundary conditions and the first five mode shapes are presented in graphs.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.207-212
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• 2001

This paper considers a pipeline conveying one-dimensional unsteady flow inside. The dynamics of the fluid-pipe system is represented by two coupled equations of motion for the transverse and axial displacements, which are linearized from a set of partial differential equations which consists of the axial and transverse equations of motion of the pipeline and the equations of momentum and continuity of the internal flow. Because of the complex nature of fluid-pipe interactive mechanism, a very accurate solution method is required to get sufficiently accurate dynamic characteristics of the pipeline. In the literatures, the finite element models have been popularly used for the problems. However, it has been well recognized that finite element method (FEM) may provide poor solutions especially at high frequency. Thus, in this paper, a spectral element model is developed for the pipeline and its accuracy is evaluated by comparing with the solutions by FEM.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.12 s.243
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• pp.1574-1585
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• 2005

In this paper, a spectral element model is developed for the uniform straight pipelines conveying internal unsteady fluid. Four coupled pipe-dynamics equations are derived first by using the Hamilton's principle and the principles of fluid mechanics. The transverse displacement, the axial displacement, the fluid pressure and the fluid velocity are all considered as the dependent variables. The coupled pipe-dynamics equations are then linearized about the steady state values of the fluid pressure and velocity. As the final step, the spectral element model represented by the exact dynamic stiffness matrix, which is often called spectral element matrix, is formulated by using the frequency-domain solutions of the linearized pipe-dynamics equations. The FFT-based spectral dynamic analyses are conducted to evaluate the accuracy of the present spectral element model and also to investigate the structural dynamic characteristics and the internal fluid transients of an example pipeline system.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1666-1671
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• 2003

Exact dynamic stiffness model for a uniform straight pipeline conveying unsteady fluid is formulated from a set of fully coupled pipe-dynamic equations of motion, in which the fluid pressure and velocity of internal flow as well as the transverse and axial displacements of the pipeline are all treated as dependent variables. The accuracy of the dynamic stiffness model formulated herein is first verified by comparing its solutions with those obtained by the conventional finite element model. The spectral element analysis based on the present dynamic stiffness model is then conducted to investigate the effects of fluid parameters on the dynamics and stability of an example pipeline problem.

• Advances in concrete construction
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• v.9 no.1
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• pp.103-113
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• 2020

This paper deal with the critical fluid velocity response of nanocomposite pipe conveying fluid based on numerical method. The pressure of fluid is obtained based on perturbation method. The motion equations are derived based on classical shell theory, energy method and Hamilton's principle. The shell is reinforced by nanoparticles and the distribution of them are functionally graded (FG). The mixture rule is applied for obtaining the equivalent material properties of the structure. Differential quadrature method (DQM) is utilized for solution of the motion equations in order to obtain the critical fluid velocity. The effects of different parameters such asCNT nanoparticles volume percent, boundary conditions, thickness to radius ratios, length to radius ratios and internal fluid are presented on the critical fluid velocity response structure. The results show that with increasing the CNT nanoparticles, the critical fluid velocity is increased. In addition, FGX distribution of nanoparticles is the best choice for reinforcement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.925-928
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• 2005

In this paper, a spectral element model is developed for the uniform straight pipelines conveying internal unsteady fluid. The spectral element matrix is formulated by using the exact frequency-domain solutions of the pipe-dynamics equations. The spectral element dynamic analyses are then conducted to evaluate the accuracy of the present spectral element model and to investigate the vibration characteristics and internal fluid transients of an example pipeline system.

• Computers and Concrete
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• v.21 no.6
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• pp.717-726
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• 2018

Concrete pipelines are the most efficient and safe means for gas and oil transportation over a long distance. The use of nano materials and nono-engineering can be considered for enhancing concrete pipelines properties. the tests show that $SiO_2$ nanoparticles can improve the mechanical behavior of concrete. Moreover, severe hazard for pipelines is seismic ground motion. Over the years, scientists have attempted to understand pipe behavior against earthquake most frequently via numerical modeling and simulation. Therefore, in this paper, the dynamic response of underwater nanocomposite submerged pipeline conveying fluid is studied. The structure is subjected to the dynamic loads caused by earthquake and the governing equations of the system are derived using mathematical model via Classic shell theory and Hamilton's principle. Navier-Stokes equation is employed to calculate the force due to the fluid in the pipe. As well, the effect of external fluid is modeled with an external force. Mori-Tanaka approach is used to estimate the equivalent material properties of the nanocomposite. 1978 Tabas earthquake in Iran is considered for modelling seismic load. The dynamic displacement of the structure is extracted using differential quadrature method (DQM) and Newmark method. The effects of different parameters such as $SiO_2$ nanoparticles volume percent, boundary conditions, thickness to radius ratios, length to radius ratios, internal and external fluid pressure and earthquake intensity are discussed on the seismic response of the structure. From results obtained in this paper, it can be found that the dynamic response of the pipe is increased in the presence of internal and external fluid. Furthermore, the use of $SiO_2$ nanoparticles in concrete pipeline reduces the displacement of the structure during an earthquake.

• Computers and Concrete
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• v.24 no.2
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• pp.125-135
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• 2019

Concrete pipelines are the most efficient and safe means for gas and oil transportation over a long distance. The use of nano materials and nono-engineering can be considered for enhancing concrete pipelines properties. the tests show that SiO2 nanoparticles can improve the mechanical behavior of concrete. Moreover, severe hazard for pipelines is seismic ground motion. Over the years, scientists have attempted to understand pipe behavior against earthquake most frequently via numerical modeling and simulation. Therefore, in this paper, the dynamic response of underwater nanocomposite submerged pipeline conveying fluid is studied. The structure is subjected to the dynamic loads caused by earthquake and the governing equations of the system are derived using mathematical model via Classic shell theory and Hamilton's principle. Navier-Stokes equation is employed to calculate the force due to the fluid in the pipe. As well, the effect of external fluid is modeled with an external force. Mori-Tanaka approach is used to estimate the equivalent material properties of the nanocomposite. 1978 Tabas earthquake in Iran is considered for modelling seismic load. The dynamic displacement of the structure is extracted using differential quadrature method (DQM) and Newmark method. The effects of different parameters such as SiO2 nanoparticles volume percent, boundary conditions, thickness to radius ratios, length to radius ratios, internal and external fluid pressure and earthquake intensity are discussed on the seismic response of the structure. From results obtained in this paper, it can be found that the dynamic response of the pipe is increased in the presence of internal and external fluid. Furthermore, the use of SiO2 nanoparticles in concrete pipeline reduces the displacement of the structure during an earthquake.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.4 s.109
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• pp.387-393
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• 2006

In this paper, a spectral element model is developed for the uniform straight pipelines conveying internal unsteady fluid flow. The spectral element matrix is formulated by using the exact frequency-domain solutions of the pipe-dynamics equations. The spectral element dynamic analysis is then conducted to evaluate the accuracy of the present spectral element model and to investigate the vibration characteristics and internal fluid characteristics of an example pipeline system.

• Wind and Structures
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• v.30 no.2
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• pp.133-140
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• 2020

In this paper, critical fluid velocity and frequency of laminated pipe conveying fluid are presented. Each layer of the pipe is reinforced by functionally graded carbon nanotubes (FG-CNTs). The internal fluid is assumed turbulent and the induced forces are calculated by momentum equations. The pipe is resting on viscoelastic foundation with spring, shear and damping constants. The motion equations are derived based on classical shell theory and energy method. Differential quadrature method (DQM) is used for solution and obtaining the critical fluid velocity. The effects of volume percent and distribution of CNT, boundary condition, lamina layer number, length to radius ration of pipe, viscoelastic medium and fluid velocity are shown on the critical fluid velocity. Results show that with increasing the lamina layer number, the critical fluid velocity increases.