• 한국유체기계학회 논문집
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• 제14권6호
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• pp.76-84
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• 2011

The effect of inlet velocity profile on the heat transfer coefficient in a rotating smooth channel was investigated experimentally. Three simulated inlet flow conditions of fully developed, uniform, and distorted inlet conditions were tested. The Reynolds number based on the channel hydraulic diameter was ranged from 10,000 to 30,000 and the transient liquid crystal technique was used to measure the distribution of the heat transfer coefficient in the rotating channel. Results showed that the overall heat transfer coefficient increased as the Reynolds number increased. Also, the distribution of the heat transfer coefficient was strongly affected by the inlet flow condition. Generally, the fully developed flow simulated condition showed the highest heat transfer coefficient.

• 한국농공학회논문집
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• 제60권4호
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• pp.83-91
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• 2018

Land reclamation, coastal construction, coastline extension and port construction, all of which involve dredging, are increasingly required to meet the growing economic and societal demands in the coastal zone. During the land reclamation, a portion of landfills are lost from the desired location due to a variety of causes, and therefore prediction of sediment transport is very important for economical and efficient land reclamation management. In this study, laboratory disposal tests were performed using an open channel, and suspended sediment transport was analyzed according to flow velocity and grain size. The relationships between the average and standard deviation of the deposition distance and the flow velocity were almost linear, and the relationships between the average and standard deviation of deposition distance and the grain size were found to have high non-linearity in the form of power law. The deposition distribution of sediments was demonstrated to have log-normal distributions regardless of the flow velocity. Based on the experimental results, modeling of suspended sediment transport was performed using deep neural network, one of deep learning techniques, and the deposition distribution was reproduced through log-normal distribution.

• 한국자동차공학회논문집
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• 제7권6호
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• pp.174-181
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• 1999

in order to elucidate the characteristic of velocity distribution of the cavity air. Exploratory tests were conducted on an unloaded rolling radial tire operated at various speeds and inflation pressure. A hot-wire anemometer, rotating with the tire, was used to measure the flow velocity inside the tire cavity. Tow different types of experiments were performed ; one for the effects of rolling speed with constant inflation pressure, the other for the various cavity pressures with constant rolling speed. Experimental results are given as plots of the mean velocity distributions versus the distance from the rim. It is observed that the magnitude of mean velocity in the cavity air shows increasing natures with the increasing of the inflation pressures and rolling speeds.

• Journal of Mechanical Science and Technology
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• 제17권6호
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• pp.925-934
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• 2003

An experimental study is performed to investigate the characteristics of near wake flow behind a circular cylinder with serrated fins using a constant temperature anemometer and flow visualization. Various vortex shedding modes are observed. Fin height and pitch are closely related to the vortex shedding frequency after a certain transient Reynolds number. The through velocity across the fins decreases with increasing fin height and decreasing fin pitch. Vortex shedding is affected strongly by the velocity distribution just on top of the finned tube. The weaker gradient of velocity distribution is shown as increasing the freestream velocity and the fin height, while decreasing the fin pitch. The weaker velocity gradient delays the entrainment flow and weakens its strength. As a result of this phenomenon, vortex shedding is decreased. The effective diameter is defined as a virtual circular cylinder diameter taking into account the volume of fins, while the hydraulic diameter is proposed to cover the effect of friction by the fin surfaces. The Strouhal number based upon the effective diameters seems to correlate well with that of a circular cylinder without fins. After a certain transient Reynolds number, the trend of the Strouhal number can be estimated by checking the ratio of effective diameter to inner diameter. The normalized velocity and turbulent intensity distributions with the hydraulic diameter exhibit the best correlation with the circular cylinder's data.

• 플랜트 저널
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• 제6권2호
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• pp.62-69
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• 2010

The stability of coal pulverizer in the 800 MW coal-fired plants is vital to maintain their performance. Thus, this study analyzed the uneven abrasion of the deflector and coal spillage due to the air velocity maldistribution in the vane wheel of a bowl-type pulverizer as it is a possible cause for problems of facility using pulverized coal. In addition, air flow in the underbowl of a bowl-type pulverizer was studied to check air velocity maldistribution in the vane wheel using numerical method. In an attempt to correct the maldistribution of air velocity, air flow of the modified duct vane was studied as enlarging the length of the duct vanes installed at the air inlet duct of the pulverizer and increasing the angle of inclination. It was found that modified duct vane make the velocity distribution at the vane wheel uniform. formed by the duct vanes installed at the air inlet duct of the pulverizer and swirling flow is the major factor in making the velocity distribution of vane wheel exit uniform. This can prevent the uneven abrasion of the deflector, which is one of the components inside the pulverizer and coal spillage.

• 한국기계가공학회지
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• 제21권9호
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• pp.28-34
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• 2022

The flow at the top surface of the hopper is of particular industrial interest. Previously, the velocity distribution inside the hopper was predicted using the simple, void and spot models, which are equations for the particle flow field. However, because these equations cannot predict the velocity distribution at the top surface, a new equation has been recently proposed. This study employed the discrete element method with the changed shape of the particles. Based on the results, the shape of the particle had no effect on the discharge angle and shape of the velocity distribution; however, it greatly affected the size of the velocity distribution and bed thickness of the flowing particles. Therefore, in the future, it is necessary to modify the theoretical equation by considering the shape of the particles.

• 한국기계가공학회지
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• 제7권2호
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• pp.31-37
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• 2008

In this paper, we analyzed the dynamic behavior of magnetic fluid in a circular pipe with multiple permanent magnets. Magnetic fluid react on magnetic field against the normal fluid. In other words, magnetic fluid flow has the electromagnetism and fluid mechanics. So magnetic fluids has studied about the fluids properties and experiment. In this paper we studied the magnetic fluids velocity and pressure distribution for the novel type actuator. Because the velocity and pressure distribution is the important element of the magnetic fluids flow. First, we analyzed the Maxwell equation for the multiple permanent magnet and then concluded the governing equations for the magnetic fluid flow using the equation of Navier-Stokes. And, we simulated the dynamic behavior of magnetic fluid flow using the FEM(Finite Element Method). And we illustrated the relation between magnetic field and dynamic behavior of magnetic fluid flow.

• Journal of Mechanical Science and Technology
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• 제17권2호
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• pp.296-309
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• 2003

The periodicity of the physiological flow has been the major interest of analytic research in this field up to now Among the mechanical forces stimulating the biochemical reaction of endothelial cells on the wall, the wall shear stresses show the strongest effect to the biochemical product. The objective of present study is to find the effects of velocity waveform on the wall shear stresses and pressure distribution along the artery and to present some correlation of the velocity waveform with the clinical observations. In order to investigate the complex flow phenomena in the bifurcated tube, constitutive equations, which are suitable to describe the rheological properties of the non-Newtonian fluids, are determined, and pulsatile momemtum equations are solved by the finite volume prediction. The results show that pressure and wall shear stresses are related to the velocity waveform of the physiological flow and the blood viscosity. And the variational tendency of the wall shear stresses along the flow direction is very similar to the applied sinusoidal and physiological velocity waveforms, but the stress values are quite different depending on the local region. Under the sinusoidal velocity waveform, a Newtonian fluid and blood show big differences in velocity. pressure, and wall shear stress as a function of time, but the differences under the physiological velocity waveform are negligibly small.

• 설비공학논문집
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• 제18권10호
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• pp.819-825
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• 2006

In a SOFC/GT (solid oxide fuel cell/gas turbine) hybrid power generation system, the recuperator is an indispensible component to enhance system performance. Since the expansion ratio to the recuperator core is very large, generally, the effective header design to distribute the flow uniformly before entering the core is crucial to guarantee the required performance. In the present study, we focus on the design of a diffuser type recuperator header with a 90 degree turn inlet port. To reduce the flow separation and recirculation flows, multiple horizontal vanes are used. The number of horizontal vanes is varied from 0 to 24. The air flow velocity is measured at 40 points just behind the core outlet by using a hot wire anemometer. Then, the flow non-uniformity is evaluated from the measured flow velocity. The experimental results showed that inlet air velocity did not effect on relative flow non-uniformity. According to increasing the number of horizontal vanes, flow non-uniformity reduced about $40{\sim}50%$ than without using horizontal vanes.

• 한국정밀공학회지
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• 제17권1호
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• pp.209-215
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• 2000

Precision forging technology that can control flow velocity of workpiece have been developed to minimize the amounts of machining. To get the uniform rib length, flow velocity distribution is needed to be estimated and controlled. Computer-aided design is known for very effective to estimate the deformation behavior and design the die for controlling the flow velocity. In this study, die design to control the deformation velocity are investigated using the DEFORM-2D about rib-web shape parts. Also we can get uniform rib length by enforcing the back pressure at end section of rib. The applied load of back pressure farming is lower than that of conventional forging. These results are analysed and confirmed by the experiment.