• Solar Energy
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• v.10 no.1
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• pp.47-56
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• 1990

The aerodynamic performances of Darrieus wind turbine were studied through the wind tunnel model tests and its analytical aerodynamic streamtube model. Hence, analytical streamtube model which is based on momentum and blade element theory is considered and the formulated model was generalized in non-dimensional type to predict the aerodynamic characteristics of Darrieus wind turbine. The analytical model was justified through the wind tunnel model tests for several experimental conditions but in the limited rages. These satisfactory comparative studies between the wind tunnel tests and the analytical predictions can be utilized for the basic reliable design of Darrieus wind turbine.

• Journal of the Korean Society of Visualization
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• v.8 no.1
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• pp.39-45
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• 2010

The optimal design is needed for the blade geometry of the quad-rotor blades which is mainly used for Unmanned Aerial Vehicle. To do this, it is important to analyze the wakes under the blades. In the present study, the flow around the rotating blades was analyzed using PIV(Particle Image Velocimetry) and CFD(Computational Fluid Dynamics). The maximum axial velocity was measured at about 60% position toward the radial direction of the blade. The positions of vorticities in the test section obtained by PIV and CFD were turned out to be almost alike. The values in the difference of pressure coefficients at the upper and the lower blades were increased depending on the radial direction. Then, the values were decreased at the blade tip. The data of the flow analysis in the present study are expected to be served as the design of blades and ducts for the thrust improvement in the future.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.6
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• pp.784-789
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• 2018

Accurate aerodynamic characterization of projectile is crucial for successful development of munition. The aerodynamic characterization of fin stabilized projectile is more difficult than characterization of traditional symmetric ballistic projectile. Instrumented free flight experiments were conducted to quantify rolling behavior of fin stabilized projectile. The instrumented projectiles were launched from a rifled tube and the onboard sensor data were acquired through a telemetry transmitter. Roll rate was measured for fin stabilized projectile by means of an angular rate sensor. And, roll damping coefficients were estimated from onboard sensor data acquired during gun firing and trajectory analysis of mathematical model.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.3
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• pp.197-209
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• 2018

In this study, numerical analyses on Quad Tilt Rotor(QTR) are carried out to investigate the interference effect of components and effect of operating condition during forward flight. Actuator Surface Method(ASM) which is implemented in an open source CFD code, OpenFOAM, is used to calculate the flow field around QTR with high computational efficiency. The lift of the front and rear wing is found to increase or decrease depending on the rotation direction of the rotor. At the rear wing, the interference effects of the front and rear rotor appear as a combined manner. Performance change due to the phase difference is found to be insignificant. For both rotors, the locally higher thrust is generated by the blockage effect of the wing. The interference effect of wake from the front nacelle contributes to higher local thrust for the rear rotor compared to the front rotor. And it is observed that the amplitude of thrust oscillation can decrease depending on the phase difference between the rotors. Aerodynamic performances of both rotors and the entire aircraft were compared and analyzed for various operating conditions.

• Journal of Biosystems Engineering
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• v.13 no.2
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• pp.18-27
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• 1988

The basic model of impeller was developed for the theoretical analysis of performance. The developed model was tested with two different blade radius of curvature based on the pumping efficiency under the operating conditions in Korea. And the pump performance of the impeller was also tested for the various speeds. The results obtained are summarized as follows; 1. There was no significant effect on the different blade radius of curvatures on the discharge and pump efficiency. 2. Head and power requirement was increased in proportion to the blade radius of curvature. 3. In the mathematical approach of the blade radius of curvature, the method of involute curve was more recommendable as compared with the method of circular arc curve. 4. The pump efficiency of the model impeller developed based on the theoretical analysis increased about 10% more than that of the existing impeller.

• Journal of Energy Engineering
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• v.29 no.1
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• pp.34-43
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• 2020

A study has been done for self-starting torque of vertical axis wind turbine blade. It is especially concentrated to evaluate the torque coefficient before starting rotation. Two different aerofoils(AMI903 and AMI904) are proposed to benchmark the possible best blade(supercritical airfoil) for self-starting performance. Torque coefficients in the tangential direction of rotation are given with respect to the angle of attack in terms of drag coefficient and lift coefficient. Torque coefficient shows that the effect of Reynolds number is minimal. The thicker blade(AMI904) between two different proposed airfoils has bigger torque coefficient, which is attributed to lower lift coefficient and higher drag coefficient.

• The Journal of the Acoustical Society of Korea
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• v.33 no.6
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• pp.358-365
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• 2014

When a ship propeller having wing type sections rotates at high speed underwater, local pressure on the blade decreases and various types of the cavitation inevitably occur where the local pressure falls below the vapor pressure. Fundamentally characteristics of the cavitation are determined by the shapes of the blade section and their operating conditions. Underwater noise radiated from a ship propeller is directly connected to the occurrence of the cavitation. In order to design low noise propeller, it is preferentially demanded to figure out key features: how the cavity is generated, developed and collapsed and how the effect of viscosity works in the process. In this study, we first perform inviscid analysis of the partial cavity generated on two dimensional hydrofoil. Secondly, viscous analysis using FLUENT with different turbulence and cavitation models are presented. Results from both approaches are also compared and estimated.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.1118-1122
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• 2005

수중보는 하천, 하수관 또는 인공수로에 건기시 유지수량을 확보할 목적으로 설치되며 제한 범위 이상의 물이 유입되는 경우 원활한 치수를 위하여 이를 자동적으로 방출시키도록 자동으로 수문을 개폐시키는 장치가 필요하다. 보통 10년 주기 내외의 평균 강우량에 맞추어서 그 용량이 결정되어야 경제성을 확보할 수 있게 된다. 그러나 10년 주기의 평균 강우량을 초과하는 강우가 발생할 경우에 유입되는 전체 수량을 유입시키면 해당 기기에 상당한 손상을 입히게 된다. 또한 재현기간을 너무 길게 잡을 경우, 해당 수처리의 설치비용이 과다하게 되고, 경제성이 낮아질 수 밖에 없다. 따라서 수처리를 위한 장치의 규모는 적정한 재현기간에 맞추어 설계하고, 재현기간을 초과하여 강우가 발생할 경우 강우 유입을 우회시킬 필요가 있게 된다. 이와 같이 수량을 우회 또는 통과시킬 목적으로 초과유량을 방출할 수 있는 완충회전수문 실험 모형을 제작하여 여러 차례의 실험을 토대로 한계수심 및 충격량을 이론적으로 산정하였다.

• Korean Journal of Soil Science and Fertilizer
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• v.41 no.6
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• pp.374-378
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• 2008

For the standard method of collecting the run-off, it is consumed the high cost and much effort to install and to manage this instrument. Because the all the soil and water from reservoir tank must be eliminate after their measurement of amount of soil loss and run-off and installed the reservoir tank at regular size in the experimental field. Therefore, objective of this study was to compare its efficacy between the standard method and a flow rotate divider for ontinuously collecting and measuring the soil loss and run-off in order to conveniently conduct the field experiment of the lysimeters. For collecting the sampling of soil loss and run-off from agricultural land with invariable ratio, a flow rotate divider was consisted with a 8 blades of round plate sloped in order to collect the invariable ratio of soil and water at lowest part from round plate by the law of gravity. For comparing its accuracy in the batch scale experiment, it shown that there was significantly a positive linear corelation ($r=0.997^{***}$) between flowing and sampling amounts with adjusting the range from 1 to $10L\;min^{-1}$ with flowing rate. In collecting ratio in the field experiment, it observed that the more its accuracy had, the more soil loss and run-off.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.11
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• pp.965-972
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• 2016

This paper presents results of flight experiments on a navigation algorithm including multiplicative extended Kalman filter for estimating attitude of the guided munition. The filter describes orientation of aircraft by data fusion with low-cost sensors where measurement update is done by multiplication, rather than addition, which is suitable for quaternion representation. In determining attitude from vector observations, the existing approach utilizes a 3-axis accelerometer as a 2-axis inclinometer by measuring gravity to estimate pitch and roll angles, while GNSS velocity is used to derive heading of the vehicle. However, during accelerated maneuvers such as coordinated flight, the accelerometer provides inadequate inclinometer measurements. In this paper, the measurement update process is newly defined to complement the vulnerability by using different vector observations. The acceleration measurement is considered as a result of a centrifugal force and gravity during turning maneuvers and used to estimate roll angle. The effectiveness of the proposed method is verified through flight experiments.