• Journal of computational fluids engineering
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• v.13 no.1
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• pp.7-13
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• 2008

Several high resolution schemes such as OSHER, MUSCL, SMART, GAMMA, WACEB and CUBISTA are comparatively studied with respect to the accurate capturing of fluid interfaces throughout the application to two typical test cases of a translation test and a collapsing water column problem with a return wave. It is accomplished by implementing the high resolution schemes in the in-house CFD code(PowerCFD) for computing 3-D flow with an unstructured cell-centered method and an interface capturing method, which is based on the finite-volume technique and fully conservative. The calculated results show that SMART scheme gives the best performance with respect to accuracy and robustness.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.8
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• pp.612-618
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• 2003

A hybrid vibration control scheme using ER fluid and PZT patches is proposed. Dynamic characteristics of the beam embedded with the ER fluid can be controled by changing the strength of the electric field applied on the ER fluid, thus provides a mean to avoid the resonance. It was found that active vibration control of the structure embedded with ER fluid failed to suppress the vibration excited with broad band frequency due to the limited change of the dynamic characteristics of the structure. To compensate this limited effect of the control scheme with ER fluid alone, PPF control using PZT patches as sensors and actuators is added to construct a hybrid controller. Experimental results suggests that proposed hybrid controller is effective to suppress the additional resonance vibration that appears when each controller is used alone.

• Journal of computational fluids engineering
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• v.8 no.4
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• pp.26-33
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• 2003

Smart UAV Development Program, one of the 21c Frontier R&D Program sponsored by MOST(Ministry of Science and Technology), was launched in 2002 As an air vehicle for the Smart UAV, CRW(Canard Rotor/wing) concept was one of the candidates compared in trade-off study. The CRW concept has not only been proven completely but its aerodynamic characteristics not known in detail yet. Two calculation methods were adopted in this study to obtain aerodynamic data for the CRW First method was the superpose DATCOM method which is capable of three lifting sufaces, and second one is the full Navier-Stokes computation around CRW configuration using overset grid method. Basic aerodynamic characteristics of the CRW configuration was analyzed and the minimum drag level with lift to drag ratio is presented. The peculiar flow characteristics around rotor/wing and hub were also examined and considered in the configuration design.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.348.1-348
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• 2002

This paper deals with the vibration reduction of the hull mount system of ship structures brought by ER smart structures. The hull mount is used to isolate the vibration form the immersed structures. Utilizing the tunable characteristics of ER fluids, ER insert are made In the hull mountint structure. Different types of ER inserts are proposed and the vibration characteristics are investigated. (omitted)

• Journal of Drive and Control
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• v.5 no.3
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• pp.2-8
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• 2008

• Journal of computational fluids engineering
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• v.8 no.3
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• pp.32-40
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• 2003

CFD analyses of the three-dimensional turbulent flow in the impeller and diffuser of an axial flow pump including suction and discharge parts are presented and compared with experimental data. The purpose of the current study is to validate the CFD method for the performance analysis of the main coolant pump for SMART and to investigate the effect of suction and discharge shapes on the pump performance. To generate a performance curve, not only the design point but also the off-design points were computed. The results were compared with available experimental data in terms of head generated. At the design point, the analysis accurately predicts the experimental head value. In the range of the higher flow rates, the results are also in very good agreement with the experimental data, in magnitude but also in terms of slope of variation. For lower flow rates, the results shows that the analysis considering the suction and discharge well describe the typical S-shape performance curve of the axial pump.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.210-215
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• 2002

MR(Magnetorheogical) fluid composed of fine iron powders dispersed in silicon oil is utilized to many smart structures and devices because of its significant rheological property change by the application of an external magnetic field. When we deal with the shock wave attenuation of warship structures, we should be able to characterize the high frequency behavior of MR fluids. So far, however, many efforts have been focused on the material characterization of MR fluids at low frequencies below 100Hz. In this paper, the MR fluid property characterization at high frequency region is performed. An experimental setup based on wave transmission technique is made and the storage modulus as well as the loss modulus of MR fluids are found from the measured data of speed sound and attenuation. Details of the experiment are addressed and the obtained storage and loss moduli are addressed at $50kHz{\sim}100kHz$.

• Journal of the Korean Solar Energy Society
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• v.28 no.1
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• pp.9-17
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• 2008

An experimental investigation has been carried out to study the effects of different working fluids on the behavior and thermal performance of a hi-directional thermodiode. The thermodiode was made up of two rectangular loops mounted between a collector plate and a radiator plate. Rotatable joints between the horizontal and inclined segments of the loops enable easy alteration of the direction of heat transfer. The loops and the tank were filled with a working fluid for effective heat transfer when the thermodiode was forwarded biased. Six different working fluids were tested with thermal conductivity values ranging from 0.1 to $0.56W/m-^{\circ}C$, thermal expansion coefficient values ranging from $1.8\;{\times}10^{-4}$ to $1.3\;{\times}\;10^{-3}\;K^{-1}$, and kinematic viscosity values ranging from $0.65\;{\times}\;10^{-6}$ to $100\;{\times}\;10^{-6}\;m^2/s$. Especially, mixtures of $Al_2O_3$ (30nm Particle) in deionized water have been tested for the volumetric ratios of 0.01, 0.02, 0.03, 0.1, 0.2%. Each experiment was carried out after the loop was filled with a working fluid for effective heat transfer and the thermodiode was forwarded biased. The solar thermodiode was heated by a radiant heater consisting of 20 halogen lamps that generated a heat flux of about $1000\;W/m^2$ on the collector surface. Results are given in terms of temperature development in different parts of the loop as heat is delivered from its hot end to the surrounding atmosphere by the radiator made of copper plates.

• 한국전산유체공학회:학술대회논문집
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• 2001.10a
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• pp.118-125
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• 2001

The performance prediction of SMART MCP was performed using a computational fluid dynamics code. General capacity-head performance curve of MCP, which is provided to other design branches as design input, was obtained and it showed the typical type of axial pump performance curve. When four MCPs operate in parallel and one of them stops while the others continue to operate, SMART requires reduced power operation. A procedure for predicting the performance of SMART MCP for that case was developed and verified with available experimental data. An analysis based on the developed procedure was performed for two cases; the impeller of sloped MCP is fixed or free to rotate in reverse direction. According to the results, $73\%$ flow rate of normal operation enters the reactor core in the case of the locked impeller. In case of the impeller free rotation, the flow rate entering the reactor core is $62.8\%$.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.191-196
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• 2007

With the development of micro electronic circuits and optical equipment, the demand for developing smart munitions with the ability to autonomously search for and attack targets has increased. Since the electronic components within smart munitions are affected by high temperatures, pressure, and impulsive forces upon the combustion of gunpowder, stability and reliability need to be secured for them. Securing those stability and reliability requires soft recovery system which can decelerate smart munitions. A theoretical analysis of flow is performed for the secure recovery of bullets on the basis of Navier-Stokes equation for compressible fluids. The inner pressure on a pressure tube, the speeds of bullets, and the deceleration of munitions are calculated theoretically. Theoretical results are compared with the data from the experiment with soft recovery system set up at the laboratory.