• International Journal of Naval Architecture and Ocean Engineering
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• 제2권2호
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• pp.104-111
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• 2010

The complete avoidance of cavitation, as a result of gap flow between the fixed and movable portion of a horn type rudder system, is difficult. To reduce gap flow, it is a common practice to attach a half round prismatic bar that protrudes beyond the concave surface of the horn facing the gap and laid along the centerplane of the rudder. However the employment of such a device does not always yield satisfactory results. Previously, the authors have shown that a pair of blocking bars, attached on the convex surface of the movable portion, better enhance the blocking ability of gap flow to that of a single centre bar installed on the concave surface. This also circumvents difficulties that might occur in practical applications. In the present study, a series of numerical computations show that flow injected into the gap of a rudder may also block the flow within, without employment of any physical devices, such as a half circular bar. This study also shows that the combination of flow injection and blocking bars may result in the synergic augmentation of blocking efficiency of gap flow, as demonstrated in computations for a three dimensional rudder system.

• 실천공학교육논문지
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• 제6권1호
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• pp.43-49
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• 2014

몰입을 할 줄 아는 능력과 습관이 한 개인의 삶의 질을 평가하는 중요한 지표가 될 수 있다고 알려져 있다. 또한 청소년기로부터 성인 초기로 전환하는 중요한 시기에 있는 대학생의 몰입 경험은 일차적으로 전공 탐구와 진로 결정에 크게 영향을 주고 향후 질 높은 삶이 전개에도 영향을 준다. 본 연구에서는 공과대학 메카트로닉스공학부생들이 PLC (Programmable Logic Controller) 실습을 통하여 몰입을 경험하는가를 조사하였다. 이를 위해 몰입 요건을 분석하여 PLC실습에서 몰입학습이 일어나도록 강의계획을 수립하고, 학습여건을 만들고, 수업 난이도를 조정하였다. 그리고 한 학기 동안 PLC실습을 수강한 학생들 90명에 대하여 Likert식 5점 척도 설문으로 몰입의 효과를 조사하였다.

• International Journal of Fluid Machinery and Systems
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• 제10권2호
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• pp.99-118
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• 2017

ECHO progress was defined to depict the rotordynamic pump theory development. Experience (E) era for pumps lasted nearly one and a half hundred years before the Industrial Revolution due to the low rotation speed of motor and undeveloped manufacture ability. Classic (C) theory referring to quasi-static performance as well as the items those were not able to be steadily resolved under the level were briefly and sophisticated outlined. Since 1962, flow instabilities and the dynamic responses had come into main attention with the development of the modern technologies such as ballistic missile, rocket and space shuttle main engine, and were finally heuristically (H) elucidated by talented scholars and researchers. Recently, new applications for the pumps open (O) to the surrounding fluid and diversity of the medium such as multiphase flow need more studies and some examples were briefly introduced to display the potential problems lastly.

• Wind and Structures
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• 제18권5호
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• pp.529-548
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• 2014

This article presents the unsteady aerodynamic performance of crosswind stability obtained numerically for the ATM train. Results of numerical investigations of airflow past a train under different yawing conditions are summarized. Variations of occurrence flow angle from parallel to normal with respect to the direction of forward train motion resulted in the development of different flow patterns. The numerical simulation addresses the ability to resolve the flow field around the train subjected to relatively large yaw angles with three-dimensional Reynolds-averaged Navier-Stokes equations (RANS). ${\kappa}-{\varepsilon}$ turbulence model solved on a multi-block structured grid using a finite volume method. The massively separated flow for the higher yaw angles on the leeward side of the train justifies the use of RANS, where the results show good agreement with verification results. A method of solution is presented that can predict all aerodynamic coefficients and the wind characteristic curve at variety of angles at different speed.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2004년도 추계학술대회 논문집
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• pp.48-51
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• 2004

Chemical Mechanical Polishing(CMP) is popularly used in production of semiconductor because of large area polishing ability probability of improvement for more integrated circuit. However, present CMP processing causes some non-uniformity errors which can be critical for highly integrated circuit. Previous studies predict that flow-field of slurry during CMP can create non-uniformity, but no quantitative measurement has conducted. In this study, using PIV, slurry velocity flow-field during CMP is measured by changing the ratio of RPM of pad and carrier with tuned PIV system adequate for small room in CMP machine and Cabot's non-groove pad Epad-A100. The result show that velocity of slurry is majorly determined by pad-rpm and the ratio of between carrier and pad rpm make some changes in streamlines.

• Journal of Mechanical Science and Technology
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• 제14권5호
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• pp.553-561
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• 2000

This paper presents a numerical model of multi phase flow of the mixtures of molten material-liquid-vapor, particularly in thermal nonequilibrium. It is a two-dimensional, transient, three-fluid model in Eulerian coordinates. The equations are solved numerically using the finite difference method that implicitly couples the rates of phase changes, momentum, and energy exchange to determine the pressure, density, and velocity fields. To examine the model's ability to predict an experimental data, calculations have been performed for tests of pouring hot particles and molten material into a water pool. The predictions show good agreement with the experimental data. It appears, however, that the interfacial heat transfer and breakup of molten material need improved models that can be applied to such high temperature, high pressure, multi phase flow conditions.

• International Journal of Automotive Technology
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• 제7권2호
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• pp.139-143
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• 2006

As an automobile tends to be high grade, the needs for more luxurious interior and comfortable HVAC system are emerged. The defrosting ability is another major factor of the performances of HVAC system. The present work is to simulate the flow and the temperature field of cabin interior during the defrost mode. The three-dimensional incompressible Navier-Stokes equations and energy equation were solved on the multi blocked grid system by the iterative time marching method and AF scheme, respectively. The present computations were validated by the comparison of the temperature field of a driven cavity and velocity field of 1/5 model scale of an automobile. Generally good agreements were obtained. By the present computation, the complicated features of flow and temperature within the automotive cabin interior could be well understood.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 A
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• pp.509-511
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• 2001

In the competitive electricity market, various pricing methods are developed and practiced in many countries. Among these pricing methods, marginal loss factor(MLF) can be applied to reflect the marginal cost of network losses. For the calculation of MLF, power flow method has been used. However, it shows some shortcomings such as necessity of regional reference node, and absence of an ability to consider network constraints. The former defect might affect adversely to the equity of market participants and the latter might generate an inappropriate price signal. To overcome these defects, the utilization of optimal power flow(OPF) is suggested in this paper. 30-bus system is used for the case study to compare the MLF by the power flow and the OPF method for 24-hour dispatching and pricing.

• 지구물리와물리탐사
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• 제7권1호
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• pp.33-40
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• 2004

Numerical and laboratory studies have been conducted to test the ability of Electrical Resistance Tomography-a technique used to map the electrical resistivity of the subsurface-to delineate contaminant plumes. Two-dimensional numerical models were created to investigate survey design and resolution. Optimal survey design consisted of both downhole and surface electrode sites. Resolution models revealed that while the bulk fluid flow could be outlined, small-scale fingering effects could not be delineated. Laboratory experiments were conducted in a narrow glass tank to validate theoretical models. A visual comparison of fluid flow with ERT images also showed that, while the bulk fluid flow could be seen in most instances, fine-scale effects were indeterminate.

• 한국생산제조학회지
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• 제21권1호
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• pp.150-155
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• 2012

Water jet propulsion system has low efficiency than screw propeller at low speed, but has been applied in high speed ship due to its better cavitation performance and high rotation capacity. In this study, a numerical analysis was conduct to understand the flow in the propulsion system of 200HP grade water jet for small ship. As the result, it could be confirmed that total pressure and force of the flow was increased through the impeller and the straight-ability of discharging flow to outlet was improved by guide vane. Also, the reliability of numerical analysis was secured by comparing peripheral velocity calculated by design values with that calculated by numerical analysis.