• Journal of Korea Multimedia Society
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• v.8 no.10
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• pp.1322-1328
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• 2005

The circulation flows passing through the Ekman boundary layer on the rotating disk and transfer the angular momentum into the interior region of the container. Consequently, the circulation enhances the momentum transfer and the interior fluid is divided by a propagating shear front. This investigation focuses on computer vision and image processing technique for analysis of Non-Newtonian Fluids. To visualize marching velocity shear front for the transient flow, a particular shaped particles and light are used. To validate the proposed method, quantitative image are compared with the optical data acquired by a direct measurement of LDV (Laser Doppler Velocimetry).

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.12
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• pp.1087-1096
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• 2011

The purpose of current study is to develop and verify the newly developed solver for analyzing rotor flow using the open-source code. The algorithm of standard solver, OpenFOAM, is improved to analyze the rotor inflow with and without fuselage. For the calculation of the rotor thrust, the virtual blade method based on the blade element method is employed. The inflow velocities on the rotor disk used to specify the effective angle of attack, have been included in the solver. The results of the current rotor inflow analysis are verified by comparing with other experimental and numerical results. It was confirmed that the modified solver provides satisfactory results for rotor-fuselage interaction problem.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.7
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• pp.652-659
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• 2011

A computational system to predict flowfield and infrared signature in aircraft exhaust system is developed. As the first step, a virtual mission profile is considered and an engine is selected through a performance analysis. Then a nozzle that meets the requirement of each mission is designed. The internal flow in the exhaustion nozzle at the maximum thrust is analyzed using a state-of-the-art CFD code. In addition, a system to combine information of the skin temperature distribution of the nozzle and after-body surface with an infrared prediction code is developed. Finally, qualitative results for the infrared signature reduction design are obtained by investigating the infrared signature level under various conditions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.2
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• pp.226-233
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• 1999

An experimental study has been performed on natural convection heat transfer with a rapid crust formation in the molten metal pool of a low Prandtl number fluid. Two types of steady state tests, a low and high geometric aspect ratio cases in the molten metal pool, were performed. The crust thickness by solidification was measured 88 a function of boundary surface temperatures. The experimental results on the relationship between the Nusselt number and Rayleigh number In the molten metal pool with a crust formation were compared with existing correlations. The experimental study has shown that the bottom surface temperature of the molten metal layer, in all experiments. is the major influential parameter in the crust formation, duo to the natural convection flow. The Nusselt number of the case without a crust formation in the molten metal pool is greater than that of the case with the crust formation at the same Rayleigh number. The present experimental results on the relationship between the Nusselt number and Rayleigh number In the molten metal pool match well with Globe and Dropkin's correlation. From the experimental results, a now correlation between the Nusslet number and Rayleigh number in the molten metal pool with the crust formation was developed as $Nu=0.0923(Ra)^{0.302}$ ($2{\times}10^4< Ra<2{\times}10^7$).

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.4
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• pp.491-499
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• 2010

Heat transfer performance of tube bundles have long been investigated since they were widely used. Most of previous experimental and numerical works for tube bundles were performed with tube diameter in the range of 25~51mm and Reynolds number of $8.000{\leq}Re{\leq}30.000$. Recently, tube bundles with small diameter tube collects interests since the mini-channel tube provides higher compactness. The present work aims to investigate the applicability of previous correlations available in the open literature to the tube bundles with small diameter of 1.5mm and $3.000{\leq}Re{\leq}7.000$. A commercial CFD package was used to analyze the thermal-hydraulic performance of them. The results show that the Zukauskas correlation developed for larger diameter tube and higher Reynolds number are still in good agreement with them within the discrepancy of 4.7%. The analyses also show that the Nuselt number increases with a decrease in the longitudinal pitch.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.6
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• pp.347-355
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• 2016

This study presents a Lattice Boltzmann Method (LBM) coupled with a momentum-exchange approach/fictitious domain (MEA/FD) method for the simulation of particle suspensions. The method combines the advantages of the LB and the FD methods by using two unrelated meshes, namely, a Eulerian mesh for the flow domain and a Lagrangian mesh for the solid domain. The rigid body conditions are enforced by the momentum-exchange scheme in which the desired value of velocity is imposed directly in the particle inner domain by introducing a pseudo body force to satisfy the constraint of rigid body motion, which is the key idea of a fictitious domain (FD) method. The LB-MEA/FD method has been validated by simulating two different cases, and the results have been compared with those through other methods. The numerical evidence illustrated the capability and robustness of the present method for simulating particle suspensions.

• Journal of the Korea Computer Graphics Society
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• v.24 no.4
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• pp.21-27
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• 2018

In this paper, we propose a real-time interaction method using user's mouth wind in mobile device. In mobile and virtual reality, user interaction technology is important, but various user interface methods is still lacking. Most of the interaction technologies are hand touch screen touch or motion recognition. In this study, we propose an interface technology that can interact with real time using user's mouth wind. The direction of the wind is determined by using the angle and the position between the user and the mobile device, and the size of the wind is calculated by using the magnitude of user's mouth wind. To show the superiority of the proposed technique, we show the result of visualizing the flow of the vector field in real time by integrating the mouth-wind interface into the Navier-Stokes equations. We show the results of the paper on mobile devices, but can be applied in the Agumented reality(AR) and Virtual reality(VR) fields requiring interface technology.

• Journal of the Korean Institute of Gas
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• v.5 no.3 s.15
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• pp.1-8
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• 2001

This study was carried out for the purpose of determination of maintenance period and investigation of weak point due to freeze when the gas heater of KOGAS valve station Is not operated in winter season. 3-dimensional non-linear numerical simulation was conducted in order to predict the time and location which bath water in heater reaches to ice point. FLUENT V 5.0, commercial code, is used for thermal fluid flow analysis. We thought this was problem of heat conduction solving the energy equation and modeled gas heater by using the real geometry and scale for performing the 3-dimensional simulation. It was analyzed complex heat transfer phenomena considering convection due to air on surface, conduction in insulation material, natural convection of liquid in heater and heat loss through the pipe.

• Journal of the Korean GEO-environmental Society
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• v.15 no.4
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• pp.37-41
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• 2014

Pulse electrokinetic technology is proposed for improving the dewatering-process from clay-sandy soil. Proposed electrokinetic technology is to be the dewatering process due to fluid movement of current flow for the stability of clay-sandy soils. Samples produced in this study were completed to verify the proposed performance for 7 days by gradually increasing the pressure to the final pressure of 30 psi ($2.11kgf/cm^2$) through the compression process. In this study, pulse electrokinetic treatment and conventional continuous electrokinetic treatment are tested and observed, respectively. The condition of continuous electrokinetic treatment is a continuous process during 48 hours. And the condition of pulse electrokinetic treatment system is to interrupt the power three times for 48 hours, every 8 hours. These treatments are that the voltage gradient is 3 V/cm. As a result, the efficiency of pulse electrokinetic is similar to the continuous electrokinetic. The power consumption efficiency of pulse electrokinetic is better than continuous electrokinetic.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.11
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• pp.1091-1097
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• 2017

Sales of commercial-type cooling fans intended for application in military electronics are often discontinued during equipment production. This results in requirements for alternative fan selection as well as equipment performance and reliability tests, such as high-temperature operation testing. This study deals with alternative fan selection and verification methods that can be used during the production process. First, an alternative fan was selected by calculating the flow and pressure required to effectively cool the equipment, then the feasibility of the selected fan was verified using a reliable CFD heat dissipation analysis model. Following this, a high-temperature operation test was performed using the alternative fan in the equipment. Results demonstrated that the equipment satisfied its required function in a high-temperature environment, and the main parts as well as internal air temperature were found to be thermally stable.