• 한국가구학회지
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• 제12권1호
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• pp.1-9
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• 2001

This study was carried out to elucidate the relationship between wood anatomy and the water flow path in P. koraiensis and L. leptolepis. through the experiment of penetration of the dye solution. The experiment was performed by permeating 1% acid, alkali and direct solution into the xylem just after being cut. The results obtained were summarized as follows : 1. In P. koraiensis and L. leptolepis, the dye solution penetrated into sapwood and annual rings adjacent to cambial zone were only dyed according to ascent of tree height. 2. The penetrability of latewood was better than that of earlywood. 3. In P. koraiensis and L. leptolepis, the main water flow path in longitudinal direction was the trachied and that in transverse direction was ray trachied and ray parenchyma. Also, the dye solution was found in resin canal. 4. P. koraiensis was more permeable than L. leptolepis. 5. Among the acid, alkali and direct dye solution, the acid dye solution was the most permeable.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.689-694
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• 2003

An iterative modal analysis approach is developed to determine the effect of transverse open cracks on the dynamic behavior of simply supported pipe conveying fluid subject to the moving mass. The equation of motion is derived by using Lagrange's equation. The influences of the velocity of moving mass and the velocity of fluid flow and a crack have been studied on the dynamic behavior of a simply supported pipe system by numerical method. The presence of crack results in higher deflections of pipe. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments i.e. the crack is modelled as a rotational spring. Totally, as the velocity of fluid flow and the crack severity are increased, the mid-span deflection of simply supported pipe conveying fluid is increased. The time which produce the maximum dynamic deflection of the simply supported pipe is delayed according to the increment of the crack severity.

• 대한조선학회논문집
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• 제44권4호
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• pp.370-378
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• 2007

In this study. a numerical analysis has been performed for the turbulent flow around a 15,000TEU twin-skeg container ship using a commercial CFD code. FLUENT. The computed results have been compared with the model test data from MOERI. We investigated viscous resistance coefficient. wake distribution and characteristics of the shear flow according to the grid numbers. Although the free surface is approximated by the plane of symmetry in this work. the calculated axial velocity and transverse vector show a good agreement with the MOERI experimental data except for the region of 0.9 level of axial velocity at the propeller plane. The numerical analysis show that commercial CFD code is useful tool for the evaluation of complex hull form with twin-skegs.

• 한국안전학회지
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• 제28권5호
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• pp.54-60
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• 2013

In this study, a finite element model based on the SU/PG scheme was developed to solve shallow-water equations and the influences of parameters and internal boundary conditions on depth-averaged flow behavior were investigated. To analyze the effect of roughness coefficient and eddy viscosity on flow characteristics, the developed model was applied to rectangular meandering channel with two bends, and transverse velocities and water depth distributions were examined. As the roughness coefficient adjacent to wall increased, the velocities near the wall decreased, and the reduced velocities were compensated by the expanding mid-channel velocities. In addition, the flow characteristics around a circular cylinder were analyzed by varying the internal boundary conditions as free slip and no slip. The assignment of slip condition changed the velocity distribution on the cylinder surface and reduced the magnitude of the shear stress up to one third.

• 한국가시화정보학회지
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• 제7권2호
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• pp.28-34
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• 2010

Two turbulent jet with different sinusoidal nozzle exit configurations of in-phase and $180^{\circ}$ out-of-phase were investigated experimentally using a smoke-wire method and a hot-wire anemometry. Mean velocity and turbulence intensity were measured at several downstream locations under $Re_D\;=\;5000$. For the case of in-phase nozzle configuration, the length of potential core exhibits negligible difference with respect to the transverse locations (0, $\lambda/4$ and $\lambda/2$), similar to that of a plane jet. On the other hand, a maximum difference of 30% in the potential-core length occurs for the $180^{\circ}$ out-of-phase configuration. The spatial distributions of turbulence intensities also show significant difference for the nozzle of $180^{\circ}$ out-of-phase, whereas non-symmetric distribution is observed in the near-exit region(x/D = 1) for the in-phase sinusoidal nozzle jet. Compared to a slit planc jet, the sinusoidal nozzle jets seem to suppress the velocity deficit as the flow goes downstream. The sinusoidal nozzle jet was found to decrease turbulent intensity dramatically. The flow visualization results show that the flow characteristics of the sinusoidal nozzle jet are quite different from those of the slit plane jet.

• Journal of Advanced Marine Engineering and Technology
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• 제12권1호
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• pp.53-61
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• 1988

Most of the recent for the flow field hydrofoil in partially cavitating condition are the ones which are linearized, and the problem of cavity end region for hydrofoil is not verified. This paper deals with a study on characteristics of end region flow field for partially cavitating hydrofoil by using a characteristics of shear turbulence flow and nonlinear cavity flow theory. The results obtained as follows : 1) Shear layer thickness is decreased gradually going to the end section of hydrofoil. When attack angle is large, it is appeared largely at the region of partial cavitation after its collapsing. 2) The fluctuation velocity of a second-degree relative direction have minimum value at the front of hydrofoil or at the end of hydrofoil. The difference for the validity of attack angle is appeared largely at the surrounding of .chi.$_{e}$ point. 3) The fluctuation velocity of transverse direction decrease from the maximum thickness of cavitation to the end of hydrofoil, but it undergoes largely the effect of pressure recovery. The difference is larger at the region of partial cavitation after its collapsing than at the of hydrofoil. 4) The distribution of Reynolds stress have maximum values at the region of partial cavitation after its collapsing and the end of foil, and the larger attack angle, the larger the distribution of value.e.

• Journal of Ship and Ocean Technology
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• 제12권1호
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• pp.1-15
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• 2008

An edgetone is the discrete tone or narrow-band sound produced by an oscillating free shear layer, impinging on a rigid surface. In this paper, 2-dimensional edgetone to predict the frequency characteristics of the discrete oscillations of a jet-edge feedback cycle is presented using lattice Boltmznan model with 21 bits, which is introduced a flexible specific heat ratio y to simulate diatomic gases like air. The blown jet is given a parabolic inflow profile for the velocity, and the edges consist of wedges with angle 20 degree (for symmetric wedge) and 23 degree (for inclined wedge), respectively. At a stand-off distance w, the edge is inserted along the centerline of the jet, and a sinuous instability wave with real frequency is assumed to be created in the vicinity of the nozzle exit and to propagate towards the downward. Present results presented have shown in capturing small pressure fluctuating resulting from periodic oscillation of the jet around the edge. The pressure fluctuations propagate with the speed of sound. Their interaction with the wedge produces an irrotational feedback field which, near the nozzle exit, is a periodic transverse flow producing the singularities at the nozzle lips. It is found that, as the numerical example, satisfactory simulation results on the edgetone can be obtained for the complex flow-edge interaction mechanism, demonstrating the capability of the lattice Boltzmann model with flexible specific heat ratio to predict flow-induced noises in the ventilating systems of ship.

• Nuclear Engineering and Technology
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• 제54권7호
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• pp.2714-2719
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• 2022

The present paper proposes some new computational methods and results in the framework of flow computation through congested domains seen as porous media, as it can be found in the core of a Pressurized Water Reactor (PWR). The flow is thus mostly governed by the distribution of pressure losses, both through the porous structures, such as fuel assemblies, and in the thin fluid layers between them. The purpose of the present paper is to consider the question of the interaction of a flow and a rod bundle from an analytical point of view gathering all the contributions through a set of equations as simple and representative as possible. It aims at demonstrating a sound understanding of the relevant phenomena governing the flow establishment in the geometry of interest instead of relying mainly on a posteriori observations obtained both experimentally and numerically. Comparison with two set of experimental results showed good agreement. The model proposed being analytical it appears easily implementable for studies needing an expression of fluid forces in a rod array as for fuel assembly bowing issue. It would be interesting to test the reliability of the model on other geometry with different P/R ratios.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.799-802
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• 2008

General behaviors based on hydraulic characteristics of natural streams and channels have been recently analyzed and developed via various numerical models. However in the states of natural hydraulics, an experimental research must be performed simultaneously with the mathematical analysis due to effects of hydraulic properties such as meander, sediment, and so on. In this study based on 2-D advection-dispersion equation, flow and tracer experiments were performed in the S-curved meandering laboratory channel with a rectangular cross-section. The channel was equipped with instrument carriages which was equipped with an auto-traversing system to be used with velocity measuring sensors throughout the depth and breadth of the flow field. To measure concentration distribution of the salt solution was adjusted to that of the flume water by adding methanol and a red dye (KMnO4) was added to aid the visualization of the tracer cloud, the tracer was instantaneously injected into the flow as a full-depth vertical line source by the instantaneous injector and the initial concentration of the tracer was 100,000 mg/l. The secondary current as well as the primary flow pattern was analyzed to investigate the flow distribution in the meandering channels. The velocity distribution of the primary flow for all cases skewed toward the inner bank at the first bend, and was almost symmetric at the crossovers, and then shifted toward the inner bank again at the next alternating bend. Thus, one can clearly notice that the maximum velocity occurs taking the shortest course along the channel, irrespective of the flow conditions. The result of the tracer tests shows that pollutant clouds are spreading following the maximum velocity lines in each cases with various mixing patterns like superposition, separation, and stagnation of pollutant clouds. Flow characteristics in each cases performed in this study can be compared with tracer dispersion characteristics with using evaluation of longitudinal and transverse dispersion coefficients(LDC, TDC). As expected, LDC and TDC in meandering parts have been evaluated with increasing distribution and straight parts have effected to evaluate minimum of LDC and TDC due to symmetric flow patterns and attenuations of secondary flow.

• Journal of applied mathematics & informatics
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• 제8권2호
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• pp.539-550
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• 2001

In the present investigation, we study the influence of a transverse magnetic field through a porous medium. Laplace transform techniques are used to derive the solution in the Laplace transform domain. The inversion process is carried out using a numerical method based on Fourier series expansions. Numerical computations for the temperature, the microrotation and the velocity distributions as well as for the induced magnetic and electric fields and carried out and represented graphically.