• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.916-921
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• 2003

In most industrial applications, the geometrical complexity is combined with the moving boundaries. These problems considerably increase the computational difficulties since they require, respectively, regeneration and deformation of the grid. As a result, engineering flow simulation is restricted. In order to solve this kind of problems the immersed boundary method was developed. In this study, the immersed boundary method is applied to the numerical simulation of stationary, rotating and oscillating cylinders in the 2-dimensional square cavity. No-slip velocity boundary conditions are given by imposing feedback forcing term to the momentum equation. Besides, this technique is used with a second-order accurate interpolation scheme in order to improve the accuracy of flow near the immersed boundaries. The governing equations for the mass and momentum using the immersed boundary method are discretized on the non-staggered grid by using the finite volume method(FVM). This study presents the possibility of the immersed boundary method to apply to the complex flow experienced in the industrial applications.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.448-453
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• 2005

Temperature Control Valve (TCV) is one of the useful temperature control devices, which is used to control constant temperature of working fluid in power and chemical plants and domestic water supply systems. TCV is composed of body, cylinder and piston, and the body shape has a symmetrical H-type. In general, it has several inlet and outlet holes, and its shape is like as tubular sleeve. The piston has three rings two rings of the end of piston have the function of controlling inlet flow rate with hot and cold working fluids, the center ring has the function of preventing hot and cold water from intermixing. Consequently, the shapes of piston and cylinder are the main design parameters in the performance of TCV. In this study, numerical analyses were carried out with two different piston and cylinder shapes to investigate the functions as a temperature control valve and the flow characteristics according to piston opening grade in TCV. Using a commercial code, FLUENT, velocity and pressure fields in TCV are obtained under steady, standard $k -{\epsilon}$ turbulence model and no-slip condition.

• Composites Research
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• 제12권1호
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• pp.11-18
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• 1999

섬유로 강화된 열가소성 복합재의 성형과정 중에는 유동특성에 미치는 금형내 충전패턴의 제어나 섬유배향 및 섬유함유율과 같은 성형공정 인자들의 영향을 예측하는 것이 필요하다. 본 연구에서는 등온상태에서 두께가 얇거나 두꺼운 성형품을 압축성형하는 경우에 발생하는 유동선단과 압력분포, 속도구배 등을 예측함을 목적으로 한다. 이때 복합재는 비압축성 뉴턴유체로 하였으며, 성형공정 변수들에 미치는 미끄럼 지배상수 $\alpha$와 점성비 $\zeta$의 영향에 대해서 고찰한 내용을 보고한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.492-497
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• 2013

In this study, a parametric study is performed to investigate the squeal noise of an automobile water pump. The squeal noise studied in this paper is generated by the self-excited torsional resonance of the rotating shaft, and this noise is related to the stick-slip phenomenon of the mechanical seal in the water pump. The mechanical seal friction has the characteristics of the negative velocity-gradient. The equations of motion of multiple-degree-of-freedom torsional vibration model is constructed by the Holzer's method and then the equation is transformed to an equivalent single-degree-of-freedom torsional resonance simulation model. A squeal noise criteria is determined by the simulation model to perform the parametric study. The design parameters(the mass moment of inertia of the pulley, the mass moment of inertia of the impeller, the length of the shafts, the radius of the shafts, spinning speed of the shafts, the position of the mechanical seal, radius of the mechanical seal, and normal load of the mechanical seal) are investigated to confirm the stability for the squeal noise.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.1019-1022
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• 2002

Pipe-cutting machines have been used in many fields. Recently, an automatic pipe-cutting machine that uses magnet has born developed. In this paper, a magnetic-type automatic pipe-cutting machine that attaches itself and performs unmanned cutting process is proposed. It is designed that there is a room at the bottom of its body to contain a magnet. And it uses magnetic force between the magnet and the pipe surface to prevent slip and to attach the machine to the pipe against gravity. Also the magnetic force is adjustable by changing the gap between the magnet and the pipe. This machine is, however, necessary to control cutting velocity for the elevation of work efficiency and the adjustable faculties. During pipe cutting process, the gravity acting on the pipe-cutting machine widely varies. That is, the cutting machine gets fast when moving from the top to the bottom of the pipe and slow when moving from the bottom to the top. Actually the system is kind of a non-linear system where the gravity is function of climbing angle of the cutting machine along the pipe. Especially jerking motion is critical. Therefore, authors design the non-linear controller that estimates the current position of the machine along the pipe and compensates the effect of gravity in this paper. It receives the feed back signal from the encoder.

• Tribology and Lubricants
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• 제29권3호
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• pp.167-170
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• 2013

The friction behavior of human skin is determined by the complex interplay of the material and surface properties of the skin, as well as the contacting material, and strongly depends on the contact parameters (e.g., pressure and sliding velocity) and the presence of substances such as water, sweat, or skin surface lipids at the interface. Including a study on the effect of a surface's physical roughness for skin sliding over the surface, various studies have been conducted to understand human tactile sensibility. However, to investigate products in relation to human tactile sensibility, more objective research is needed. This study performed sliding experiments between the skin and the surfaces of phone cases to understand how the texture, friction, and stick-slip characteristics are related. Eight phone case surfaces with different topologies and chemical (or mechanical) compatibilities with skin were prepared and tested multiple times.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 D
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• pp.2569-2571
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• 2000

In the vehicle steering system, we can consider two methods to steer the vehicle. One is a front wheel steering(FWS), the other is a four wheel steering(4WS). The four wheel steering method has been recently introduced to improve the steering performance. In this paper, we present a design of the four wheel steering controller. First, we constructed the neural network two degree of freedom PID controller to control the 4WS system. Then we compared the performance of conventional PID controller with our proposed controller in terms of yaw rate and side slip velocity. The computer simulation results show that 4WS system controlled by the proposed controller has well driving performances than the other.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.552-557
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• 2007

Due to the recent improvement of living standard of residential buildings, the requirements of the thermal comfort and energy saving in heating system have been raised. The radiant floor heating system has been widely used as a residential heating method, which has been modernized to use hot water running into the tubes embedded in the floor structure. The uniform flow distribution is very important factor for a radiant floor heating system such as a blood vessel system in human body. Therefore, it is necessary to investigate the operating characteristics to develop an optimal radiant floor heating system. In this study, numerical analyses were carried out, using a commercial CFD code, FLUENT, to obtain the velocity distribution under steady, three-dimensional, standard k-$\varepsilon$ model and no-slip condition. Results are graphically depicted with various parameters.

• 대한조선학회논문집
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• 제29권4호
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• pp.132-145
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• 1992

추진 효율 향상을 위한 대칭형 전류 고정날개-프로펠러 추진시스템의 설계, 이론성능해석 및 모형시험 과정을 정리하였다. 프로펠러 후류에서의 회전방향 운동에너지 회수를 통한 추진효율 향상을 도모하기 위하여 프로펠러 전방에 반대방향의 회전 속도를 주기 위한 고정날개를 설치하였다. 모형시험 결과 대칭형 전류 고정날개 추진시스템이 단독프로펠러에 비하여 3%정도 추진효율의 향상이 있음을 확인하였다. 실선 장착시에는 선체 반류에서의 난류 강도증가 및 레이놀드수 증가에 따른 고정날개 표면에서의 박리현상 감소에 의하여 고정날개 항력계수가 감소할 것으로 추정되며 그에 따라 본 추진시스템의 추진효율 증가량이 더욱 커지리라 판단된다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 D
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• pp.1984-1986
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• 2001

In order to provided continuous solutions, latest developing navigation systems tend to integrate GPS receiver with INS or DR. Using the GPS carrier-phase measurements, an attitude GPS receiver with three antennas obtain the 3-dimensional attitude such as roll, pitch, and heading as well as position and velocity. With these angle measurements, in the attitude GPS/INS integrated system, attitude or gyro errors can be directly compensated. In this paper, we develop an integrated navigation system that combines attitude GPS receiver with INS. The performance of real-time integrated navigation system is determined by not only the implements of integration filter but also the synchronization of measurements. To meet these real-time requirements, the navigation software is implemented in multi-tasking structure in this paper. We also employ time-synchronization technique in the multi-sensor fusion. Experimental results show that the performance of the attitude GPS/INS integrated system is consistent even when cycle-slip occurs in carrier-phase measurements.