• 대한조선학회논문집
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• 제41권3호
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• pp.13-21
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• 2004

This paper deals with a theoretical and experimental method for the design of a biased asymmetric pre-swirl stator propulsion system which is an energy saving device by recovering a propeller rotational energy. In the case of slow-speed ships, the upward flow is generated along the afterbody hull form at the propeller plane. The generated upward flow cancels the rotating flow of the propeller at the starboard part while it increases at port part. The present biased asymmetric pre-swirl stator propulsion system consists of three blades at the port and one blade at the starboard which can recover the biased rotating flow effectively. This paper provides the design concept which gives more simple and a high degree of efficiency and the experimental results for the compound propulsion system.

• 한국해양공학회지
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• 제33권5호
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• pp.377-386
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• 2019

Flexible composite propellers have a relatively large deformation under heavy loading conditions. Thus, it is necessary to accurately predict the deformation of the blade through a fluid-structure interaction analysis. In this work, we present an LST-FEM method to predict the deformation of a flexible composite propeller. Here, we adopt an FEM solver called OOFEM to carry out a structural analysis with an orthotropic linear elastic composite material. In addition, we examine the influence of the lamination direction on the deformation of the flexible composite propeller.

• 대한조선학회논문집
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• 제32권1호
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• pp.58-69
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• 1995

본 논문에서는 이상유체모델에서의 비선형 자유표면파의 발생, 전파 및 상호간섭에 대한 비정상 문제의 수치해법을 개발하였다. 본 수치해법은 매 시간 스텝에서 비선형 축차해법을 이용한 음함수적(implicit)방법이다. 속도장함수를 구하기 위하여 경계접합좌표계를 도입한 유한차분법을 이용하였다. 본 수치해법의 유효성과 효율성의 검증을 위하여 타원형 유체의 변형과 바닥의 일부분이 올라옴으로서 발생하는 자유표면파의 생성에 대한 두 가지 계산결과를 보여준다.

• 대한조선학회논문집
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• 제34권3호
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• pp.9-18
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• 1997

복합추진장치가 포함된 경우와 포함되지 않은 경우의 축대칭 물체 주위 유동특성을 조사하기 위한 실험적 수치적 연구가 수행되었다. 축대칭 물체주위 유동특성 파악을 위해 선박해양공학연구센터의 캐비테이션 터널에서 표면압력분포와 LDV 장치를 이용한 주위유속분포 계측 시험이 우선적으로 이루어졌으며, 비압축성 RANS 방정식을 유한체적법으로 해석하는 수치적 방법이 표준 k-${\varepsilon}$ 난류모형을 이용하여 수행되었다. 선체와 프로펠러 상호작용은 양력면이론에 의하여 계산된 유기속도를 프로펠러 면에 분포하여 경계조건으로 처리하는 방법을 택하였다. 추진장치의 여러 가지 배열변화에 따른 실험적 결과를 기반으로 타당한 수치적 방법이 개발될 수 있다고 생각된다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.472-478
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• 2004

This paper describes the characteristics of the unsteady pressure on the stator surface induced by rotor viscous wakes. The primary object of this study is to investigate the effects of axial spacing between the rotor and the stator and three-dimensional vane geometries such as stator sweep and stator lean on the unsteady pressure fluctuations on the stator vane. To predict these fluctuations, unsteady three-dimensional Navier-Stokes analyses are performed. Furthermore, a three-dimensional analytical method using unsteady lifting-surface theory is also used to elucidate the mechanism of interaction of passing rotor wakes with downstream stator. Five different fan configurations with three sets of stator geometries, which are three radial stator configurations with different axial spacing, the swept stator and the swept and leaned stator, are used for this study. It is found that, in axial spacing between rotor and stator, the effect of radial phase skew of incoming rotor wake is important for the reduction of the induced unsteady pressure in addition to the rotor wake decay. It is also shown that incorporation of stator sweep and lean is effective to reduce this unsteady pressure.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.604-609
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• 2001

This numerical analysis uses the lifting surface method and frequency-domain panel method based on the linear compressible aerodynamic theory. Increased knowledge of flow conditions within mixed-flow fan should indicates means of improving performance of these turbomachines. Thus, only an approximate solution is obtained whose prime intent is to recognize the most significant characteristics of the "ideal" geometry. For a given set of operating condition, the flow conditions within mixed-flow fan depend on the geometry of the machine (three-dimensional flow effects) and on the properties of the fluid. But most treatments of the problem have been concerned with the two-dimensional flow effects for incompressible, non-viscous fluids. Interest in the field of mixed-flow fan resulted in the undertaking of a program to develop reliable design procedures that would avoid the need for lengthy development work.

• 대한기계학회논문집B
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• 제24권3호
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• pp.325-337
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• 2000

A study was done on the numerical and experimental analyses of the aerodynamic characteristics of a counter rotating axial fan. The numerical analysis uses the frequency domain panel method developed for the aerodynamic analysis of interacting rotating systems, which is based on the unsteady lifting surface panel method. Each stage of interaction involves the solution of an isolated rotor, the interaction being done through the Fourier transform of the induced velocity field. Numerical results showed good agreements with other experimental data for single and counter rotating propeller systems. And they were compared with the experimental results of the counter rotating axial fan studied in the present paper. The performance test was carried out based on the Korean Standard (KS B 6311). It was focused on the relative efficiency increase of a counter rotating system for a single rotating one, and effects of the axial distance between the front and rear rotors on overall fan performances were investigated. As a result, it was shown that the counter rotating axial fan has the efficiency 14% higher than the single rotating one at peak efficiency points.

• 분석과학
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• 제21권3호
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• pp.222-228
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• 2008

생체피부에서의 잠재지문 현출에는 많은 제한점이 있다. 살아있는 피부는 계속적인 발한을 하고 지방친화성이 있어 흡수 및 확산에 의해 지문변화를 초래하기 때문이다. 본 연구는 사람피부에 존재하는 잠재지문의 효과적 현출방법을 알아보기 위하여 살아있는 생체피부와 피부유사 돼지피부를 이용하여 수행되었다. 피부지문현출제로는 흑색, 형광 분말 및 자석분말 그리고 Cyanoacrylate fuming을 이용하였으며 전사법으로는 전사지(lifting paper), 유리, 사진현상용 glossy paper를 이용하여 피부로부터 전사한 후 현출하였다. 살아있는 피부에 존재하는 즉시지문일 경우에는 흑색분말인 S-powder, Cyanoacrylate fuming법 및 훈증후 흑색 또는 형광분말로의 재처리에 의해 현출이 가능하였고 자석분말로의 현출로는 지문이나 배경피부에 과도하게 흡착되는 경향을 볼 수 있었으며 유류에 따라 지문이 사라짐을 알 수 있었다. 사체유사 돼지피부에서는 6시간 유류된 지문에서도 $25^{\circ}C$, 40%에서 1분간의 Cyanoacrylate fuming법 이후 흑색분말로의 재현출하였을 때 잠재지문의 현출이 가능함을 알 수 있었으며 현출된 지문영상에 다양한 스펙트럼을 이용한 감식영상의 효과적 조사파장에 대한 결과를 얻을 수 있었다.

• 한국농공학회지
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• 제14권2호
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• pp.2593-2602
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• 1972

Plastic pipes Wrapped with synthetic filter are recently used for drainage or Collecting of Underground water. But it's use is possible only for small size of diameter less than 300mm, because large size plastic pipes are not readily availabe. For large diameter infiltration gallery, porous concrete pipes are now used, but it's heavy weight brings difficulties in making, moving and setting of the pipes. With it's conventional method of filter setting, fine sands are brought into the pipes to make trouble to lifting pumps and channels Therefore, initial construction cost and maintenance cost become high. To solve-this problem, new method is developed and tested. Small PVC pipes(diameter 14mm) are assembled at the site of construction to newly devised I beam type circls. The size of circular inpiltration gallery is optionally determined by I beam type circle which support small PVC pipes and is made of PVC amterial. This gallery are wrappd with syntheitc filter to prevent sand instruction. In this test, the diameter of 300, 400, 500mm were used. I beam type circles were made with PVC plated with thickness. t=6, 9, 12mm. Water quantity collected through the PVC circulor gallery are measured and the strengths of the gallery. 1. Allowable setting depth of gallery pipe below graund for the case of t=6mm, D=500mm is 2.72m. 2. Collected water quantity depends on soil texture, depth of water grandient of water surface, filter material angle of setting etc. 3. About 126% of water quantity collected from the one gallery pipe measured in two gallery pipes of two parallel installation.

• 대한기계학회논문집B
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• 제24권7호
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• pp.895-906
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• 2000

A three dimensional linear frequency-domain lifting surface panel method was used for the aerodynamic analysis of axial flow type micro-fans. As proven by the duct modeling, the tip clearance of the micro-fans tested is large enough to ignore the calculated effect of the duct system. As the numerical results and experimental data agreed well in the operating point region, the method was applicable in the parametric studies to determine the design parameters of axial flow fans. Experiments on micro-fans were carried out based on KS B 6311. The newly designed micro-fan showed improvements in both static pressure rise and volumetric flow rate compared to the existing fans at a given operating condition. No detection of surging and the smooth characteristic curve proved the improvement in performance. To reduce the fan noise in the fan design, it was necessary to make use of the frequency spectrum analysis data. Measurement of sound pressure level for micro-fans was conducted based on KS B 6361 and KS A 0705. The peak - which occurs at blade passage frequency and its higher harmonics due to the fan noise - was not detected. This justifies the design methodology of the blade.