Papers by Author: Cheol Woo Park

Abstract: Baffles are frequently used to reduce flow speed and to change fluid passages by directly blocking oncoming flow. This study employed multi-stacked porous baffle obstructions to enhance the flow relaxations of water-soluble buoyant gases inside an odor removing basin system. We performed qualitative flow visualization by using tracing particles in working fluid to evaluate the effects of porous baffles. Particle image velocimetry technique was also employed to quantitatively analyze the flow field around the baffle regime. As a result, oncoming two-phase bubbly flow from the basin bottom regime was bent, passing the edge of a porous baffle plate. The main stream speed and momentum were effectively reduced by the installed porous flow obstruction devices.

Abstract: The flow structure inside a water basin that, serves as a water tank of a modeled washer system with an immersed coiled heater and air supply nozzle is investigated experimentally. To obtain the flow velocity field, particle image velocimetry is employed, and different view-point sections are analyzed. A large-scale vertical flow structure, which is attributed to the strong air jet flow enhancement, causes the development of a 3D mixing layer in the entire flow regime. Although a coiled heater can provide buoyancy to the working fluid, the bubbly flow structure significantly dominates this stage by supplying air from the bottom nozzles.

Abstract: A tube furnace is a heat treatment device in which a specimen is heated in the presence of an inert gas using electric heating coils embedded in a thermally insulating matrix. Heat flux and temperature gradients of sample during heat treatment in a tube furnace depend on the gas and wire velocities. These parameters were used in this paper for a 2-D axisymmetric numerical study to determine an optimized relationship between the temperature and the sample wire motion. The results show that wire velocity considerably affected the wire temperature distribution and increased the gas temperature to some extent. The phenomenon resulted in the shifting of the heating zone on the wire surface and occurrence of an inner convection heat transfer.

Abstract: In this paper, we proposed a method of monitoring human driver by reconstructing trajectories which transportation vehicle followed. For safety and management of logistic transportation, it is important to monitor the states of driving behavior through the whole course of path. Since many accidents occur due to the reckless driving of the driver every year, continuous monitoring of the status of commercial vehicles is needed for safety through the entire path from start point to the destination. To monitor the reckless driving, we tried to monitor the trajectory of the vehicle by using vehicle's lateral acceleration signal. Using the correlation between steering angle and lateral acceleration, we could find the relationship between steering angle and acceleration, and finally it is possible to estimate the global direction of vehicle maneuvering. We conducted experiments to find the history of vehicle position on the curved road using Kalman Filter, and classified steering wheel condition (over-steering, and under-steering). The method is applied to central safety management system for safety control of vehicles transporting toxic gases.

Abstract: In the present study, we experimentally investigated the roll stability recovery performance of a vehicle at various tilting angles. The vehicle was ultimately targeted to contain a velocity-field measurement system in underwater conditions, which should confirm stationary buoyancy during measurement. We employed two small gear-rack ax mountings on a weighted mass as the actuating system inside the bluff-body. Speed and movement were feedback controlled by the activating electronic motor system. The feedback algorithm used tilting action signals from an inclinometer sensor installed in the central region of the vessel shell. As a result, the bluff-body vessel effectively recovered self-stabilizing positions against the tilting action.

Abstract: In the present study, we have simulated stress characteristics and vibration modes in the back plate of head-stack driving motor of 2.5 inch small sized hard disk drives (HDDs). The magnets in head-stack driving motor have large magnetic fields, and therefore, the resulting large force may induce fracture and deformation in the back plate of the motor. Since the high-speed motion of head-stack motor generates high frequency vibration, we analyzed the vibration mode to avoid resonant frequency. ANSYS software was used in this study to check the deformation of back plate with the following design parameters: thickness of plate, the number of support beams, and the width of support beams. From the vibration mode analysis, we obtained a stable plate shape whose operating frequency is off the resonant frequency.

Abstract: Biological flows, especially blood flow, have attracted a great deal of attention from fluid engineering and hemodynamic investigation fields with advances in bio-technology. The flow of blood carries dissolved gases, nutrients, hormones, and metabolic waste through the circulatory system in the human body. In the present study, the characteristics of blood flow inside a microchannel are investigated by using a micro-particle image velocimetry (micro-PIV) and an optical image processing technique. The motion of red blood cells (RBCs) was visualized with a high-speed CCD camera. The microchannel is made of polydimethylsiloxane (PDMS) material and a slide-glass is attached to the top. The thickness of the margin cell depletion layer is calculated from an acquired raw image through the image processing method, with variations in microchannel width.

Abstract: In the present study, the flow structure inside the refrigerating compartment of a scaleddown display cooler model was investigated experimentally using the particle image velocimetry (PIV) method, which is a reliable velocity field measurement technique. In addition, we also carried out flow visualization and computer simulations regarding the movements of thermo-fluid inside a display cooler. As a result, the velocity field measurement shows a large scale vortical flow structure inside the refrigerating compartment due to the entrained flow, thus penetrating a base plate through the open inlet gap.