• 한국산학기술학회논문지
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• 제20권6호
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• pp.390-395
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• 2019

수중운동치료는 물의 저항을 이용하여 충분한 운동 효과를 낼 수 있어서 관절염이나 재활치료를 받아야하는 환자들에게 긍정적인 효과를 가진다. 하지만 효과에 대한 국내 연구는 미비한 실정이고, 그 효과에 대한 근본적인 원인규명은 아직까지 확실하지 않다. 따라서 본 연구에서는 수중운동 효과의 근본적인 원인을 파악하기 위해 실제 환경과 비슷한 조건으로 Unsteady fluid flow simulation을 진행했다. 해석 모델은 실제 손을 모델링하였고, 손가락 마디에 가해지는 압력변동을 the methods of computational fluid로 분석했다. 손의 수중운동 시, 피부 표면속도와 유동 저항에 의하여 손가락 사이에 다양한 크기의 와류가 발생한다. 와류에 의해 약 -500Pa부터 +500Pa 정도의 압력이 가해지고, 방향을 전환하는 부분에서는 최소 -2000Pa에서 최대 +2000Pa까지의 양압과 음압이 지속적으로 반복됐다. 또한 손가락 마디마다 20Hz ~ 70Hz의 진동수를 가진 압력 변동이 지속적으로 가해졌다. 이러한 지속적인 압력 변동은 손가락 마디에 직접적인 마사지 효과를 제공하고, 관련 부위의 혈액순환에 긍정적인 영향을 미친다고 판단된다.

• 한국자동차공학회논문집
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• 제18권5호
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• pp.115-123
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• 2010

Cool-down performance after soaking is important because it affects passenger's thermal comfort. The cooling capacity of HVAC system determines initial cool down performance in most cases, the performance is also affected by location, and shape of panel vent, indoor seat arrangement. Therefore, optimal indoor designs are required in developing a new car. In this paper, initial cool down performance is predicted by CFD(computational fluid dynamics) analysis. Experimental time-averaging temperature data are used as inlet boundary condition. For more reliable analysis, real vehicle model and human FE model are used in grid generation procedure. Thermal and aerodynamic characteristics on re-circulation cool vent mode are investigated using CFX 12.0. Thermal comfort represented by PMV(predicted mean vote) is evaluated using acquired numerical data. Temperature and velocity fields show that flow in passenger's compartment after soaking is considerably unstable at the view point of thermodynamics. Volume-averaged temperature is decreased exponentially during overall cool down process. However, temperature monitored at different 16 spots in CFX-Solver shows local variation in head, chest, knee, foot. The cooling speed at the head and chest nearby panel vent are relatively faster than at the knee and foot. Horizontal temperature contour shows asymmetric distribution because of the location of exhaust vent. By evaluating the passenger's thermal comfort, slowest cooling region is found at the driver's seat.

• 대한기계학회논문집A
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• 제34권8호
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• pp.1091-1096
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• 2010

본 연구는 풍하중 하에서 컨테이너 크레인의 전도사고 예방을 위한 경보시스템용 기준데이터를 도출하기 위하여 수행되었다. 분석방법으로 유동구조연성해석과 풍동실험이 사용되었으며, 크레인의 안정성에 대한 풍하중의 영향을 평가하기 위하여 컨테이너 터미널에서 널리 사용되고 있는 50 톤급 컨테이너 크레인이 해석모델로 선정되고, 19 가지 풍향이 설계변수로 채택되었다. 연구방법은 먼저 경계층풍동을 사용하여 풍향에 따른 컨테이너 크레인 모형에 대한 풍동실험을 수행한 후, ANSYS 와 CFX 를 사용하여 실제 크레인의 유동구조연성해석을 수행하였다. 다음으로 유동구조연성해석을 통해 산출된 부상력과 풍동실험을 통해 도출된 부상력을 비교하여 두 방법에 있어서 차이을 보정하기 위한 식을 제시하였다.

• 한국콘텐츠학회논문지
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• 제15권1호
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• pp.31-43
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• 2015

배터리 기반의 실시간 내장형 시스템에서는 실시간성을 만족시키기 위한 고속의 성능뿐만 아니라 배터리의 수명을 늘리기 위한 높은 에너지 효율이 요구된다. 실시간 동적전압조정(Real-Time Dynamic Voltage Scaling : RT-DVS)은 이러한 두 가지 요구사항을 만족시키기 위한 핵심기술이다. 본 논문에서는 ccEDF에 기반한 고 효율의 동적전압조정 알고리듬인 EccEDF를 제안한다. EccEDF는 ccEDF의 최대 장점중 하나인 구조적 단순성을 유지하면서 ccEDF 알고리듬의 보수성에 의해 간과된 소요시간(elapsed time)을 고려하여 태스크의 종료시 슬랙에 의해 절감될 수 있는 최대 이용률을 정확하게 계산할 수 있는 알고리듬이다. 절감될 수 있는 최대 이용률은 조기종료 시점에서 잔여수행시간($C_i-cc_i$)을 잔여시간($P_i-E_i$)으로 나누어 계산할 수 있으며, 플루이드 스케줄링 모델을 이용하여 이를 증명한다. 또한 인텔사의 동적전압조정 프로세서 중 초기 모델인 PXA250과 0.28V에서 1.2V까지 폭넓은 동적전압조정 능력을 가진 최신 IA-32 프로세서의 모델을 사용한 시뮬레이션을 통해 실제 응용에서도 EccEDF가 ccEDF 보다 우수함을 입증한다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 춘계학술발표대회 논문집
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• pp.195-198
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• 2000

The process of squeeze casting for metal matrix composites (MMCs) has been simulated numerically by using finite difference method. The governing equations to describe fluid flow through porous medium and heat transfer are applied to two dimensional model which is similar to a real system. A computational code has been developed to solve this problem. The influence on infiltration kinetics and solidification time of several parameters is investigated. Cooling curves and temperature distribution with time and position is also shown. The result can be used to design the squeeze casting for MMCs.

• 한국전산유체공학회지
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• 제11권3호
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• pp.52-58
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• 2006

A numerical investigation is made of air flow in a spinner equipment used for cleanning and drying flat display panels. A unique feature of the spinner under question is the placement of a torus plate cover over the rotating plate. The turbulent flow is driven by rotation of a large disk and suction by the exhaust system connected to vacuum chamber. The flow is modelled as an axisymmetric two-dimensional flow and computation is conducted by using the FLUENT package with a version of k-$\varepsilon$ turbulence model. The required capacity of the exhaust system is assessed numerically. The usefulness of the cover in controlling air flow circulation is examined. A computational trouble shooting is attempted to resolve the problem of panel rising which occurred in real experiment.

• International Journal of Automotive Technology
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• 제6권6호
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• pp.563-570
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• 2005

A numerical study of high pressure and temperature droplet vaporization and combustion is conducted by formulating one dimensional evaporation model and single-step chemical reaction in the mixture of hydrocarbon fuel and air. The ambient pressure ranged from atmospheric conditions to the supercritical conditions. In order to account for the real gas effect on fluid p-v-T properties in high pressure conditions, the modified Soave-Redlich-Kwong state equation is used in the evaluation of thermophysical properties. Some computational results are compared with Sato's experimental data for the validation of calculations in case of vaporization. The comparison between predictions and experiments showed quite a good agreement. Droplet surface temperature increased with increasing pressure. Ignition time increased with increasing initial droplet diameter. Temporal or spatial distribution of mass fraction, mass diffusivity, Lewis number, thermal conductivity, and specific heat were presented.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.515-516
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• 2006

Internal and inlet flows of a cross-flow fan have been visualized using a particle image velocimetry(PIV) to analyze a relationship with a performance of a room air conditioner(RAC). A test model which has a geometric similarity with the real RAC has been manufactured for the experiment and the flow characteristics have been analyzed with various flow rates and inlet grill angles for the cross-flow fan. The experimental results using the PIV technique have been compared with the existing numerical results. Also, a location and movement of an eccentric vortex which can affect the performance and noise of the RAC has been investigated by the PIV with various flow rates and inlet grill angles.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.91-94
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• 2002

It is important to develop new effective technologies for increasing the interruption capacity and reducing the size of a GCB (Gas Circuit Breaker). It is not easy to test the real GCB model in practice as in theory. Therefore, a simulation tool based on a CFD (Computational Fluid Dynamics) algorithm has been developed to facilitate an optimization of the interrupter. But the choice of grid is not at all trivial in the complicated geometries like a GCB. In this paper, we have applied a CFD-CAD integration using Cartesian cut-cell method, which is one of the grid generation techniques for dealing with complex and multi-component geometries.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.161-165
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• 2001

Recently, mega-float offshore structure is studied as one of the effective utilization of the ocean space. And mega-float structure are now being considered for various applications such as floating airports, offshore cities and so on. This mega-float structure is relatively flexible compared with real floating structures like large ships. when we estimate dynamic responses of these structures in waves, the elastic deformation is important, because vertical dimension is small compared with horizontal. The analysis of the dynamic response as it receives regular wave is studied. The finite element method is used in the analysis of structural section of this model. And the analysis is carried out using the boundary element method in the fluid division. In order to know the characteristics of the dynamic response of the mega-float structures, effects of wavelength, water depth, and wave direction on dynamic response of the floating structure are studied by use of numerical calculation.