• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.10
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• pp.994-1002
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• 2012

Acoustic power transmission loss(TL) is an important performance of the muffler system. TL will be affected by the velocity of the fluid in duct since acoustic pressure varies according to the fluid velocity. In this paper, two kinds of fluid model, potential flow and turbulent flow, for the fluid flowing in simple expansion chamber are considered. The effects of their two fluid models in acoustic TL are investigated for the straight and L-shaped simple expansion chamber. In higher frequency range, the characteristics of TL of the two fluid models show different results. The variation of TL according to the fluid velocity is shown more distinctly when turbulence model is used. Turbulent flow model should be used to obtain better estimation of acoustic TL in higher frequency range.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.5
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• pp.422-429
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• 2011

The critical fluid velocity of cantilevered cylindrical shells subjected to internal fluid flow is investigated in this study. The fluid-structure interaction is considered in the analysis. The cantilevered cylindrical shell is supported intermediately at an arbitrary axial position. The intermediate support is simulated by two types of artificial springs: translational and rotational spring. It is assumed that the artificial springs are placed continuously and uniformly on the middle surface of an intermediate support along the circumferential direction. The steady flow of fluid is described by the classical potential flow theory. The motion of shell is represented by the first order shear deformation theory (FSDT) to account for rotary inertia and transverse shear strains. The effect of internal fluid can be considered by imposing a relation between the fluid pressure and the radial displacement of the structure at the interface. Numerical examples are presented and compared with existing results.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.628-635
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• 2001

Hydrodynamic behavior and response of vertical-cylindrical liquid-storage tank is considered. The equation of the liquid motion is shown by Laplace's differential equation with the fluid velocity potential. The solution of the Laplace's differential equation of the liquid motion is expressed with the modified Bessel functions. Only rigid tank is studied. The effective masses and heights for the tank contents are presented for engineering design model.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.25-28
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• 2004

The capillary number is used to represent the mobilization potential of organic phase trapped within porous media. The capillary number has been defined by three different forms, according to types of flow velocity and viscosity used in the definition of capillary number. This study evaluated the suitability of the capillary number definitions for representing TCE mobilization by constructing capillary number-TCE saturation relationships. The results implied that the capillary number should be correctly employed, according to interest of scale and fluid flow behavior. This study suggests that the pore-scale capillary number may be used only for investigating the organic-phase mobilization at the pore scale because it is defined by the pore-velocity and the dynamic viscosity. The Newtonian-fluid capillary number using Darcy velocity and the dynamic viscosity may be suitable to quantify flood systems representing Newtonian fluid behavior. For viscous-force modified flood systems such as surfactant-foam floods, the apparent capillary number definition employing macroscopic properties (permeability and potential gradient) may be used to appropriately represent the desaturation of organic-phases from porous media.

• International Journal of Fluid Machinery and Systems
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• v.7 no.2
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• pp.68-79
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• 2014

The type of turbine developed is based on the very low head of water potential source for the electric power production. The area of research is focused for the axial water turbine that can be applied at the simple site open channel with has a very low cost and environmental impact compared to the conventional hydro installation. High efficiency of axial turbine which applied to the very low potential head will made this type of turbine can be used at wider potential site. Existing irrigation weir and river area will be the perfect site for this turbine. This paper will compare the effects of the variation of swirl velocity criterion during the design of the blade of guide vane and rotor of the turbine. Effects of the swirl velocity criterion is wider known as a vortex conditions (free vortex, force vortex and swirl velocity constant), and the free vortex is the very popular condition that applied by most of turbine designer, therefore will be interesting to do a comparison against other criterion. ANSYS Fluent will be used for simulation and to determine the predictive performance obtained by each of design criteria.

• Journal of the Korean Mathematical Society
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• v.37 no.5
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• pp.779-791
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• 2000

The nonlinear stage of the evolution of free boundary between a light fluid and a heavy fluid driven by an external force is studied by a potential flow model with a source singlarity. The potential flow model is applied to a bubble and spije evolution for constantly accelerated interface (Rayleigh-Taylor instability) and impulsively accelerated interface (Richtmyer-Meshkow instability). The numerical results of the model show that, in constantly accelerated intergace, bubble grows with constant velocity and the spike falls with gravitational acceleration at later times, while the velocity of the bubble in impulsively accelerated interface decay to zero asymp flow model for the bubble and spike for constantly accelerated interface and impulsively accelerated interface.

• 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.

• Steel and Composite Structures
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• v.23 no.6
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• pp.691-714
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• 2017

Rotating fluid induced vibration and instability of embedded piezoelectric nano-composite separators subjected to magnetic and electric fields is the main contribution of present work. The separator is modeled with cylindrical shell element and the structural damping effects are considered by Kelvin-Voigt model. Single-walled carbon nanotubes (SWCNTs) are used as reinforcement and effective material properties are obtained by mixture rule. The perturbation velocity potential in conjunction with the linearized Bernoulli formula is used for describing the rotating fluid motion. The orthotropic surrounding elastic medium is considered by spring, damper and shear constants. The governing equations are derived on the bases of classical shell theory (CST), first order shear deformation theory (FSDT) and sinusoidal shear deformation theory (SSDT). The nonlinear frequency and critical angular fluid velocity are calculated by differential quadrature method (DQM). The detailed parametric study is conducted, focusing on the combined effects of the external voltage, magnetic field, visco-Pasternak foundation, structural damping and volume percent of SWCNTs on the stability of structure. The numerical results are validated with other published works as well as comparing results obtained by three theories. Numerical results indicate that with increasing volume fraction of SWCNTs, the frequency and critical angular fluid velocity are increased.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.6
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• pp.430-437
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• 2003

A conveying fluid cantilever pipe subjected to a 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 method. The uniformly distributed tangential follower force is considered within its critical value of a cantilever pipe without moving masses, and three constant velocities and three constant distances between two moving masses are also chosen. When the moving masses exist on pipe, as the velocity of the moving mass and the distributed tangential follower force Increases. the deflection of cantilever pipe conveying fluid is decreased, respectively Increasing of the velocity of fluid flow makes the amplitude of a cantilever pipe conveying fluid decrease. After the moving mass passed upon the pipe, the tip- displacement of a pipe is influenced by the coupling effect between interval and velocity of moving mass and the potential energy change of a cantilever pipe. Increasing of the moving mass make the frequency of the cantilever pipe conveying fluid decrease.

• Communications of the Korean Mathematical Society
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• v.38 no.1
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• pp.235-242
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• 2023

In this paper, we studied several geometrical aspects of a perfect fluid spacetime admitting a Ricci ρ-soliton and an η-Ricci ρ-soliton. Beside this, we consider the velocity vector of the perfect fluid space time as a gradient vector and obtain some Poisson equations satisfied by the potential function of the gradient solitons.