• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.70-77
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• 2004

Comprehensive investigation on the outlet's geometric shapes of a centrifugal blower with higher inlet resistance than an atmospheric pressure is carried out for improvements of its performance. Most unwanted behaviors of such blower are pulsating flows because of unbalance between inflows and outflows in a scroll casing. In order to reduce this undesirable phenomenon a triump is made for both the shape of outlet duct and an accessory structure inserted in the outlet port of the blower. The modification on the shape is concerned with the contraction of cross sectional area and the attached structure is for an intentional obstruction to cause a flow resistance. The details of the modification are examined for different cases and results. The methodologies for the work are performance evaluations including noise level and velocity measurements with PIV Consequently, the performance of improved system is close to that of the system operating with atmospheric pressure at the inlet.

• Journal of the KSME
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• v.30 no.6
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• pp.548-554
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• 1990

대체에너지 기관으로서 요구되는 조건을 갖춘 스터링엔진의 이해를 돕기 위하여 기본원리, 개 발현황, 개발상 문제점 등의 기본사항을 소개하였다. 내연기관과는 달리 외연기관인 스터링엔 진은 작동유체가 밀폐공간 내에서 고. 저온 양 영역을 이동하면서 압력차를 발생시켜 일을 형성 하는 과정을 밟기 때문에 고온. 고압일수록 높은 출력이 예상되며, 전열성능과 작동저항면에서 수소나 헬륨과 같은 저분자량의 가스가 작동체로 채택되기 때문에 작동유체의 누기(leakage) 및 크랑크실의 냉각 윤활유의 작동공간으로의 누유 등은 스터링엔진의 출력 저하에 가장 큰 요인 으로 작용한다. 마찰 등 기계적 손실의 저감기술, 속도제어기술, 용도에 따른 엔진 형식 설계 기술, 구성부품 성능향상을 위한 요소기술 등의 개발이 중요한 과제가 되고 있으며, 이상 소개한 내용이 관심있는 많은 분들의 스터링엔진 연구나 이해에 도움이 될 수 있기를 바란다.

• Bulletin of the Society of Naval Architects of Korea
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• v.7 no.1
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• pp.27-36
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• 1970

선박유체역학(船舶流體力學)의 경계조건(境界條件)의 선형화(線型化)를 위한 퍼터베이션(Perturbation)방법(方法)을 따라 배를 가늘고 길게 보느냐, 엷은 수평판(水平板)으로 보느냐 등등에 따라 여러가지 다른 종류(種類)의 수학적(數學的) 정의(定義)에 따르는 이론(理論)을 추궁함으로서, 1) Neumann Ship, 2) Thin Ship, 3) Michell Ship, 4) Slender Ship 등을 이론적(理論的)인 면(面)에서와 수치계산(數値計算) 예(例)로서 비교검토(比較檢討) 하였다. 동시(同時)에 이에 따르는 "직접문제(直接問題)" "간접문제(間接問題)" 등(等)에 관(關)하여도 언급(言及)하고 그 차이점(差異點)을 지적하였다. 이에 의(依)하면 정속전진시(定速前進時)에 L/B가 10인 경우에는 최대광폭의 차(差)가 $5{\sim}8%$정도 되고 또 선수수선반각(船首水線半角)에 상당한 차(差)가 있음으로 같은 이론적(理論的)인 계산치(計算値)에 대(對)하여 저항(抵抗)은 적어도 $10{\sim}15%$정도 차(差)가 생길 것이 아닌가 보게끔 되었다.

• Journal of Ocean Engineering and Technology
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• v.15 no.2
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• pp.1-5
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• 2001

A study on the new active type oil-water separation system including the oil-water separation system of magnetic film was carried out. Separation system is composed of several active types of circulating oil separation steps and one magnetic film separation step at final stage. At the magnetic separation step, ferrofluid easily forms a weak magnetic mixture with oil, which is from the water by magnetic field gradient. The vessel has been designed to run at the maximum speed of 25 knots. And two typical forms of SWATH and Catamaran have been studied as a new type of oil recovery vessel.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2658-2663
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• 2008

In the present study, we designed a microfluidic flatform that generates monodisperse droplets with diameters ranging from hundreds of nanometers to several micrometers. To generate fine droplets, T-junction and flow-focusing geometry are integrated into the microfluidic channel. Relatively large aqueous droplets are generated at the upstream T-junction and transported toward the flow-focusing geometry, where each droplet is broken up into the targeted size by the action of viscous stresses. Because the droplet prior to rupture blocks the straight channel that leads to the flow-focusing geometry, it moves very slowly by the pressure difference applied between the advancing and receding regions of the moving droplet. This configuration enables very low flow rate of inner fluid and higher flow rate ratio between inner and outer fluids at the flow-focusing region. It is shown that the present microfluidic device can generate droplets with diameters about 1 micrometer size and standard deviation less than 3%.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2670-2675
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• 2008

We introduce a new type of surface microscope using hydrodynamic phenomena. The fluid flow through the opening of the pipette probe is blocked at short distances between the probe and the surface, thus increasing the pressure loss. Therefore, a scanning flow impedance microscope (SFIM) can image the surface topology by scanning the probe with measuring the pressure loss. The SFIM can display the topology regardless of surface hardness, surface electrical conductivity, and surrounding fluid. The present letter contains the first experimental results on surface topography obtained with this novel microscope. The preliminary results in air demonstrate the lateral resolution of the SFIM is very close to the inner diameter of the probe.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.3
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• pp.102-116
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• 1992

This report is to provide a comparison of the hydrodynamic characteristics of a single strut SWATH(Small Waterplane Area Twin Hull) model and a tandem(twin) strut SWATH model. The hydrodynamic characteristics included are the resistance in calm water, 6 degree freedom of motion responses in stationary and with forward speeds, and wave loadings etc. All these quantities are measured in the towing tank and compared with the computational results. Based on the present study, the pros and cons for single and tandem strut SWATH designs are clarified and some design suggestions are made.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.12
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• pp.1275-1281
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• 2001

Aqueous polymer solutions are known to have small pressure reduction. Paraffin slurries are known to have high thermal capacity. Paraffin particles are mixed into an aqueous polymer solution to make a new heat transfer fluid having high thermal capacity but low pressure reduction. The heat transfer characteristics of the new slurry was tested in a circular tube having a constant heat transfer boundary condition. The new slurry was found to have high Nusselt numbers as well as high thermal capacity and low pressure reduction in the laminar flow. The trends of the Nusselt numbers along the heating test section were studied for various heating conditions.

• Proceedings of the Membrane Society of Korea Conference
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• 1997.04b
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• pp.52-55
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• 1997

여과가 진행됨에 따라 막의 표면에서 발생하여 여과선속을 저하시키는 케이크층의 형성은 막을 이용한 고-액 분리공정에서 발생하는 가장 큰 문제점의 하나로서 이는 막 분리공정의 경제성을 좌우하는 중요한 인자가 된다. 이러한 문제점을 극복하기 위하여 유체와 막 사이의 상대속도를 증가시켜 여과속도를 향상시키는 십자흐름 여과, 즉 CFF(crossflow filtration)에 대한 연구가 활발히 진행되어 왔다. 그러나 이러한 심자흐름 여과에서도 막과 유체 사이의 상대속도의 증가에 한계가 있고 또한, 막의 기공보다 작은 입자가 막의 기공 내에 침투하여 막을 오염시키는 현상을 예측하기 어렵기 때문에 여과기의 설계에 있어서 많은 문제점이 발생하고 있다. 이에 오염된 막을 재생시키기 위하여 기계적.화학적인 여러 가지 방법들이 개발되고 여과선속을 향상시키는 방법이 꾸준히 연구되어 분리막 기술의 경제성을 향상시켜 왔다. 본 연구에서는 매우 안정된 유동의 하나로서 막 표면의 전단력을 향상시키는 데에 효과가 있다고 알려진 Taylor와류를 응용한 회전막 여과기를 사용하여 여러 가지 크기의 입자에 대한 여과실험을 수행함으로써 이러한 유동이 케이크의 형성에 미치는 영향을 살펴보았다. 또한 여과선속에 영향을 미치는 여러 매개인자를 알아보고 실험결과를 간단한 모델식에 적용해 봄으로써 막의 저항을 예측할 수 있는 모델식으로의 개선 방향을 제시하고자 한다.

• Journal of computational fluids engineering
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• v.21 no.3
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• pp.71-76
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• 2016

In speed skiing, aerodynamic forces play an important role in determining performance of the skier. To predict aerodynamic effects of the posture of the skier on alpine downhill skiing, we constructed equation of motion of the skier and performed the corresponding CFD simulations. Comparing drag and lift of three different skier postures, it has been shown that drag decreases significantly by tucking upper body to lower body and stretching arms forward. Also, aerodynamic lift which worked as downforce in standing posture worked upward in tuck posture, reducing friction force between snow and ski. This indicates that tuck posture have advantages over standing posture in dual mechanism, namely by reducing drag and also increasing lift. By this two-dimensional initial study we could reveal the general tendency of the aerodynamic force over the skier's body. This study not only provides a theoretical foundation for the athletes to understand the aerodynamic effects of skier postures but also shed a light on towards more accurate and rational three-dimensional CFD simulation of skiers in the near future study.