• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.1
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• pp.104-111
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• 2017

This research focuses on simulation and visualization of flow field characteristics inside a centrifugal pump. The 3D numerical analysis was carried out by using a numerical CFD tool, addressing a Reynolds Average Navier-Stock code with a standard k-${\varepsilon}$ two-equation turbulence model. The simulation accounts for friction head loss due to rough walls at suction, impeller, discharge areas and volumetric head loss at impeller wear ring. A comparison of performance curves between simulation and experimentation is included, and it reveals a same trend of those results with a small difference of maximum 5 %. At best efficiency point, velocity vectors are smooth but it changes significantly under off-design point, a strong recirculation appears at the outlet of impeller passages near tongue area. A relatively uniform preassure distribution was observed around the impeller in despite of the tongue. Within the volute, because of its geometry, spiral vortexes formed, proving that the flow field in this region was relatively turbulent and unsteady.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.327-330
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• 2006

This paper represents the numerical analysis on effects of radius ratio in a concentric annulus with a rotating inner cylinder. The numerical model consisted of two cylinder which inner cylinder is rotating and outer cylinder is fix, and the axial direction is used the cyclic condition because of the length for axial direction is assumed infinite. The diameter of inner cylinder is assumed 86.8mm, the numerical parameters are angular velocity and radius ratio. Also, the whole walls of numerical model have no-slip and the working fluid is used water at $20^{\circ}C$. The numerical analysis is assumed the transient state to observe the flow variations by time and the 3-D cylindrical coordinate system. The calculation grid adopted a non-constant grid for dense arrangement near the wall side of cylinder, the standard $k-{\omega}$ high Reynolds number model to consider the effect of turbulence flow and wall, the fully implicit method for time term and the quick scheme for momentum equation. The numerical method is compared with the experimental results by Wereley and Lueptow, and the results are very good agreement. As the results, TVF isn't appeared when Re is small because of the initial flow instability is disappear by effect of the centrifugal force and viscosity. The vortex size is from 0.8 to 1.1 for TVF at various $\eta$, and the traveling distance for wavy vortex have the critical traveling distance for each case.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.1
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• pp.75-79
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• 2007

The cathode design is one of the most important parts in order to enhance the performance of fuel cells. A 3-D model of the porous oxygen reducing cathode with perforated current collectors is analysed for the enhanced design in fuel cells. Simulation is performed using equations of electric potential balance, momentum balance, and mass balance. The gas concentrations are quite large and are significantly affected by the reactions that take place. The weight fraction of oxygen, velocity field for the gas phase, and local overvoltage are illustrated in the porous reactive cathode layer. The current density is also analysed and the result shows the distribution and variation are stated in a wide range. It is found that the rate of reaction and the current production is higher beneath the orifice, and decreases as the distance to the gas inlet increases. The significance of the results is discussed in the viewpoint of the mass transportation phenomena, which is inferred that the mass transport of reactants dictates the efficiency of the electrode in this design and at these conditions.

• Proceedings of the IEEK Conference
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• 2000.11d
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• pp.33-36
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• 2000

To create a more realistic soccer game derived from TV images, we are developing an image synthesis system that generates 3D image sequence from TV images. We propose the method for the team and the pose recognition of players in TV images. The representation includes camera calibration method, team recognition method and pose recognition method. To find the location of a player on the field, a field model is constructed and a player's field position is transformed by 4-feature points. To recognize the team information of players, we compute RGB mean values and standard deviations of a player in TV images. Finally, to recognize pose of a player, this system computes the velocity and the ratio of player(height/width). Experimental results are included to evaluate the performance of the team and the pose recognition.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1631-1635
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• 2006

본 연구에서는 레이놀즈응력모형(RSM: Reynolds Stress Model)을 이용하여 사다리꼴 개수로 흐름을 수치모의 하였다. 측벽 경사에 따른 사다리꼴 개수로 흐름을 수치모의 하였으며 계산된 평균유속 분포는 기존의 실험 결과와 비교하였다. 그 결과 개발된 레이놀즈응력이 사다리꼴 개수로 흐름을 비교적 잘 예측하는 것으로 나타났다. 또한 사다리꼴 수로에서는 직사각형 개수로 흐름과 달리 velocity dip 현상이 발생하지 않는 것으로 나타났다. 특히 측벽 경사가 32..인 사다리꼴 수로에서의 평균유속 및 바닥 전단응력 분포는 측벽 경사가 큰 경우와 다른 형태의 평균유속 및 전단응력 분포가 형성되는 것으로 나타났다.

• Tribology and Lubricants
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• v.29 no.1
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• pp.27-32
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• 2013

This study examined the effects of surface roughness in the mixed lubrication regime of smooth and rough surfaces for roller bearings. The average flow model was adopted for interaction between the flow rheology of the lubricant and the surface roughness. The average Reynolds equation and related flow factor that describes the coupled effects of surface roughness and flow rheology, the viscosity-pressure and density-pressure equations, the elastic deformation equation, and the force balance equation were solved simultaneously. The results showed that the effects of surface roughness on the film thickness and pressure distribution should be considered, especially in elastohydrodynamic lubrication contact problems.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.199-202
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• 1996

In this paper, we used the maximum likelihood method for 2-point aerodynamic model to determine the parameters of the ChangGong-91. Since the estimation from the flight test of real aircraft is the most reliable, we performed the flight test of ChangGong-91 to get the parameters such as velocity, height, 3 axis acceleration, 3 axis angular rate, pitch angle, angle of attack, temperature and so on. We recorded the flight test data in S-VHS tapes and stored them to personal computer using A/D(analog to digital) converter. Flight test was done in stall motion, and the acquired data was be processed with parameter identification method.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.211-211
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• 2000

The multiple targets tracking problem has been one of main issues in the radar applications area in the last decade. Besides the standard Kalman filtering, various methods including the variable dimension filter, input estimation filter, interacting multiple model (IMM) filter, federated variable dimension filter with input estimation, probable data association (PDA) filter etc. have been proposed to address the tracking and sensor fusion issues. In this paper, two existing tracking algorithms, i.e. the IMMPDA filter and the variable dimension filter with input estimation (VDIE), are combined for the purpose of improving the tracking performance of maneuvering targets in clutter. To evaluate the tracking performance of the proposed algorithm, three typical maneuvering patterns i.e. Waver, Pop-Up, and High-Diver motions, are defined and are applied to the modified IMMPDA filter considered as well as the standard IMM filter. The smaller RMS tracking errors, in position and velocity, of the modified IMMPDA filter than the standard IMM filter are demonstrated through computer simulations.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.7
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• pp.1294-1306
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• 1992

In order to determine the design parameters and processing conditions in injection molding, it is very important to establish the theoretical model with scientific base. In this study, a two dimensional model has been developed for the purpose and flow simulations of filling process are carried out. The moving boundary transient flow problem along the flat plane is solved efficiently by the Iterative Boundary Pressure Reflection Method which rearranges the impinged melt front along the physical boundary in scientific manner. The two dimensional modeling of filling process is applied to two examples : a three dimensional cover with two screw holes and a two-gated flat cavity with unbalanced runners. The numerical results show good agreement with experimental short shots, especially for the weldline locations and the pressure traces at various locations. They also provide the temperature, clamp force, and velocity field in the mold at different times during filling of cavity.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.1
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• pp.63-70
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• 1994

The three-dimensional incompressible clavier-Stokes equations are solved to simulate the flow field around a Wigley model with free-surface. The IAF(Implicit Approximate Factorization) method is used to show a good success in reducing the computing time. The CPU time is almost an half of that if the IAF method were used. The present method adopts the local linearization and Euler implicit scheme without the pressure-gradient terms for the artificial viscosity. Calculations are carried out at the Reynolds number of $10^6$ and the Froude numbers are 0.25, 0.289 and 0.316. For the approximations of turbulence, the Baldwin-Lomax model is used. The resulting free-surface wave configurations and the velocity vectors are compared with those by the explicit method and experiments.