• 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.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.10a
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• pp.76-76
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• 2003

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.31-32
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• 2007

• Journal of Ocean Engineering and Technology
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• v.24 no.6
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• pp.1-6
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• 2010

A far field approximate solution of the slowly varying force on a 3 dimensional offshore structure in gravity ocean waves is presented. The first order potential, or at least the far field form of the Kochin function, of each frequency wave is assumed to be known. The momentum flux of the fluid domain is formulated to find the time variant force acting on the floating body in bichromatic waves. The second order difference frequency force is identified and extracted from the time variant force. The final solution is expressed as the circular integration of the product of Kochin functions. The limiting form of the slowly varying force is identical to the mean drift force. It shows that the slowly varying force components caused by the body disturbance potential can be evaluated at the far field.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.349.1-349
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• 2002

This paper presents investigation of damping characteristics of squeeze mode type MR mount experimently. The MR mount proposed in the study has variable damping characteristics according to the applied magnetic field strength. Impact and force excitation tests were performed. The dynamic property of the mount using MR fluid was compared with that of the mount using conventional oil. (omitted)

• Proceedings of the KIEE Conference
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• summer
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• pp.986-988
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• 2004

이 전에 DC Pulse 전류로 구동하는 Magnetic Fluid Linear Pump(MFLP)를 개발하였다. 개발된 MFLP는 DC Pulse 전류에 의하여 발생하는 자기장의 분포 변화가 불연속적이게 되고, 펌핑력 또한 불연속성을 가지게 된다. 불연속적 자기장의 변화와 펌핑력의 불균일성을 저감하였다. 펌핑력을 증가시키기 위하여 AC 전류를 이용하였으며, 이에 따른 펌프의 운전 특성을 파악하기 위하여 자기장의 분포와 자성유체의 형상을 해석하였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.17 no.6
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• pp.257-269
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• 2013

In this study, the capability of an existing analysis method for the fluid-structure-soil interaction of an offshore wind turbine is expanded to account for the geometric nonlinearity and sea water drag force. The geometric stiffness is derived to take care of the large displacement due to the deformation of the tower structure and the rotation of the footing foundation utilizing linearized stability analysis theory. Linearizing the term in Morison's equation concerning the drag force, its effects are considered. The developed analysis method is applied to the earthquake response analysis of a 5 MW offshore wind turbine. Parameters which can influence dynamic behaviors of the system are identified and their significance are examined.

• Wind and Structures
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• v.36 no.6
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• pp.423-434
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• 2023

Aerodynamic force coefficients are generally obtained from traditional wind tunnel tests or computational fluid dynamics (CFD). Unfortunately, the techniques mentioned above can sometimes be cumbersome because of the cost involved, such as the computational cost and the use of heavy equipment, to name only two examples. This study proposed to build a deep neural network model to predict the aerodynamic force coefficients based on data collected from CFD simulations to overcome these drawbacks. Therefore, a series of CFD simulations were conducted using different geometric parameters to obtain the aerodynamic force coefficients, validated with wind tunnel tests. The results obtained from CFD simulations were used to create a dataset to train a multilayer perceptron artificial neural network (ANN) model. The models were obtained using three optimization algorithms: scaled conjugate gradient (SCG), Bayesian regularization (BR), and Levenberg-Marquardt algorithms (LM). Furthermore, the performance of each neural network was verified using two performance metrics, including the mean square error and the R-squared coefficient of determination. Finally, the ANN model proved to be highly accurate in predicting the force coefficients of similar bridge sections, thus circumventing the computational burden associated with CFD simulation and the cost of traditional wind tunnel tests.

• Journal of Sensor Science and Technology
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• v.32 no.5
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• pp.307-312
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• 2023

To measure the flow velocity and direction in the near field of an unmanned underwater vehicle, an optical measurement unit containing an image sensor and a phosphor-integrated pillar that mimics the neuromasts of a fish was constructed. To analyze pillar movement, which changes with fluid flow, fluorescence image analysis was conducted. To analyze the flow velocity, mean force analysis, which could determine the relationship between the light intensity of a fluorescence image and an external force, and length-force analysis, which could determine the distance between the center points of two fluorescence images, were employed. Additionally, angle analysis that can determine the angles at which pixels of a digital image change was selected to analyze the direction of fluid flow. The flow velocity analysis results showed a high correlation of 0.977 between the external force and the light intensity of the fluorescence image, and in the case of direction analysis, omnidirectional movement could be analyzed. Through this study, we confirmed the effectiveness of optical flow sensors equipped with phosphor-integrated pillars.