• Steel and Composite Structures
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• v.42 no.3
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• pp.397-405
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• 2022

The existing researches on the dynamics of the fluid-conveying pipes only focus on stability and vibration problems, and there is no literature report on the wave propagation of the fluid-conveying pipes. Therefore, the purpose of this paper is to explore the propagation characteristics of longitudinal and flexural waves in the fluid-conveying pipes. First, it is assumed that the material properties of the fluid-conveying pipes vary based on a power function of the thickness. In addition, it is assumed that the material properties of both the fluid and the pipes are closely depended on temperature. Using the Euler-Bernoulli beam equation and based on the linear theory, the motion equations considering the thermal-mechanical-fluid coupling is derived. Then, the exact expressions of phase velocity and group velocity of longitudinal waves and bending waves in the fluid-conveying pipes are obtained by using the eigenvalue method. In addition, we also studied the free vibration frequency characteristics of the fluid-conveying pipes. In the numerical analysis, we successively studied the influence of temperature, functional gradient index and liquid velocity on the wave propagation and vibration problems. It is found that the temperature and functional gradient exponent decrease the phase and group velocities, on the contrary, the liquid flow velocity increases the phase and group velocities. However, for vibration problems, temperature, functional gradient exponent parameter, and fluid velocity all reduce the natural frequency.

• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.68-71
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• 2001

This paper has been studied for a comparison of the propagation and noise characteristics between ultrasonic and electromagnetic wave for the high speed communication of the short range telemetry. We analyze the propagation depth of electromagnetic and ultrasonic wave by skin depth effect and by ultrasonic loss ratio. We also studied several effects such as near field effect in electromagnetic wave and Rayleigh scattering noise of ultrasonic wave, etc. We show the experimental results of their propagation loss and modulation experiments in water. The experimental results show that both method is good for the implementation of short range telemetry.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.7
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• pp.693-700
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• 2008

High-Pressure gas Pipeline which is buried in underground has the Possibility that will be exposed to unexpected dangerous impact of construction equipment. To protect from this kind of danger, the real-time health monitoring system of the high-pressure gas pipeline is necessary. First of all, to make the real-time health monitoring system clearly, the acoustic wave propagation characteristics which are made from various construction equipment impacts must be identified. In link of technical development that prevents the damage of high-pressure gas pipeline, this paper gives FEM(finite element method) and BEM(boundary element method) solutions to identify the acoustic wave propagation characteristic of the various impact input signals which consist of Direc delta function and convolution signal of 45 Hz square signal and random signal.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.6
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• pp.614-619
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• 1997

In this paper, radio-wave propagation characteristics in a rectangular corridor are investigated using a tunnel model of reduced dimensions. Measurements were carried out on vertical polarization characteristics in the frequency range from 2 GHz to 10 GHz. The experimental results for the propagation constant in tunnel model agree satisfactorily with theoretical prediction. It is shown that model method is applicable in determining the propagation characteristics in tunnel.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1463-1466
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• 2007

Visco-elastic damping material for reducing heavy-weight floor impact noise and vibration in reinforced concrete structures was tested according to its thickness in the damping layer. The effect of damping material was compared with 20, 15, 10 and 5mm thickness. The wave propagation characteristics was measured for suggestion of an efficient method to reduce the floor impact noise. The method was proposed using the flexural wave propagation characteristics. The result showed that reduction of the thickness of damping layer made a slight difference; the natural frequency moved to higher frequency and the amplitude increased at low frequencies with 5mm thickness of damping material.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.601-605
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• 2007

This paper describes the experimental method to monitor the structural integrity. The crack on structures changes the wave propagation characteristics of structures. To monitor this change, frequency dependent variation of dynamic stiffness of beam structures is obtained by using beam transfer function method, and its trends are compared to undamaged one for identifying the location and size of the crack. Piezoelectric actuators were used to generate flexural vibrations. It eliminated various restrictions of continuously measuring wave propagation characteristics and monitoring structural integrity. The structural integrity was identified with minimal number of measurements and smart structures employing PZT actuations.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.3
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• pp.359-368
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• 2010

This paper describes the generation and propagation of internal solitary wave in a two-layer fluid system by numerical analysis. Characteristics of interfacial soliton such as wave type, wave height, wave celerity are investigated numerically with respect to an extent of initial disturbance, fluid thicknesses of the two fluids and etc. The difference between the internal wave propagation on sloping beach and flat bottom was also examined. Laboratory experiments were conducted in the wave flume and compared with the results of numerical computation for verification.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.3
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• pp.163-170
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• 2010

Both scatterer method and transfer matrix method are compared to analyze their characteristics, which are wave propagation models due to topographic change based on plane wave approximation. Results from the scatterer method are closer to the results obtained by the more accurate existing models and it is appraised that the scatterer method gives the clearer explanation about physical process involved in the wave transformation. Since both methods have analytical solutions, in the computational point of view they are very fast and easy to be implemented. Both methods give a good prediction for wave scattering by relatively simple bedform.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.5
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• pp.819-830
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• 2016

Hydrodynamic characteristics of wave propagation through density stratification have not been identified in details. So this study conducted a numerical simulation using LES-WASS-3D ver. 2.0 for analysis of density current due to water temperature and salinity in order to analyze hydraulic characteristics under wave action in a two-layer density stratified fluid. For the validity and effectiveness of numerical wave tank used, it was compared and analyzed with the experiment to show waveform based on $3^{rd}$-order Stoke wave theory at the internal of a density stratification. Using the results obtained from numerical simulation, the surface and internal wave heights are reduced as the wave propagates in a two-layer density stratified water. And the surface or internal wave attenuation became more serious as the vorticities were increased by the velocity difference of wave propagation due to the upper-lower density difference around the interface of a density stratification. As well, the surface and internal wave attenuations became more serious with higher density difference and depth ratio between upper and lower layers when the wave propagates through a density stratification.

• Structural Engineering and Mechanics
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• v.72 no.3
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• pp.329-338
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• 2019

In this paper, the magnetic field influence on the wave propagation characteristics of graphene nanosheets is examined within the frame work of a two-variable plate theory. The small-scale effect is taken into consideration based on the nonlocal strain gradient theory. For more accurate analysis of graphene sheets, the proposed theory contains two scale parameters related to the nonlocal and strain gradient effects. A derivation of the differential equation is conducted, employing extended principle of Hamilton and solved my means of analytical solution. A refined trigonometric two-variable plate theory is employed in Kinematic relations. The scattering relation of wave propagation in solid bodies which captures the relation of wave number and the resultant frequency is also investigated. According to the numerical results, it is revealed that the proposed modeling can provide accurate wave dispersion results of the graphene nanosheets as compared to some cases in the literature. It is shown that the wave dispersion characteristics of graphene sheets are influenced by magnetic field, elastic foundation and nonlocal parameters. Numerical results are presented to serve as benchmarks for future analyses of graphene nanosheets.