• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.2
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• pp.7-13
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• 2019

This study is about distributions of heat transfer in air conditioning duct used for marine and oil drilling ship. As the convective heat transfer coefficient increased, heat transfer was conducted dynamically to inside as it exited to the outlet of duct. So, it was checked that the amount of heat transfer generated at duct increased as the convective heat transfer coefficient increased. In case the convective heat transfer coefficient was low, the temperature of duct showed the relatively high temperature distribution due to the temperature influence of internal fluid as the heat transfer between the outside and inside of the duct. In case of temperature distribution generated the volume of the duct along the change of the convective heat transfer coefficient, it was found out that the temperature descended as heat transfer was promoted and the convective heat transfer coefficient increased.

• Advances in aircraft and spacecraft science
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• v.2 no.3
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• pp.329-343
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• 2015

This study aimed to observe the effect of a novel concept (referred to as the flap extension) implemented on the leading edge of the flap of a three element high lift device. The high lift device, consisting of a flap, main element and slat is designed around an Airbus research profile for sufficient take off and landing performance of a large commercial aircraft. The concept is realised on the profile and numerically optimised to achieve an optimum geometry. Two different optimisation approaches based on Genetic Algorithm optimisations are used: a zero order approach which makes simplifying assumptions to achieve an optimised solution: as well as a direct approach which employs an optimisation in ANSYS DesignXplorer using RANS calculations. Both methods converge to different optimised solutions due to simplifying assumptions. The solution to the zero order optimisation showed a decreased stall angle and decreased maximum lift coefficient against angle of attack due to early stall onset at the flap. The DesignXplorer optimised solution matched that of the baseline solution very closely. The concept was seen to increase lift locally at the flap for both optimisation methods.

• Journal of Mechanical Science and Technology
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• v.14 no.9
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• pp.1013-1019
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• 2000

A numerical investigation was performed to determine the effect of the Gurney flap on a NACA 23012 airfoil. A Navier-Stokes code, RAMPANT, was used to calculate the flow field about the airfoil. Fully-turbulent results were obtained using the standard ${\kappa}-{\varepsilon}$ two-equation turbulence model. The numerical solutions showed that the Gurney flap increased both lift and drag. These results suggested that the Gurney flap served to increase the effective camber of the airfoil. The Gurney flap provided a significant increase in the lift-to-drag ratio relatively at low angle of attack and for high lift coefficient. It turned out that 0.6% chord size of flap was the best. The numerical results exhibited detailed flow structures at the trailing edge and provided a possible explanation for the increased aerodynamic performance.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.5
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• pp.847-852
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• 2004

The wind turbine blade is the equipment converted wind into electric energy. The effect of the blade has influence of the output power and efficiency of wind turbine. The design of blade is considered of lift-to-drag ratio. structure. a condition of process of manufacture and stable maximum lift coefficient, etc. This study is used the simplified method for design of the aerodynamic blade and aerodynamic analysis used blade element method This Process is programed by delphi-language. The Program has any input values such as tip speed ratio blade length. hub length. a section of shape and max lift-to-drag ratio. The Program displays chord length and twist angle by input value and analyzes performance of the blade.

• Journal of Industrial Technology
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• v.20 no.B
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• pp.71-76
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• 2000

A numerical investigation was performed to determine the effect of the Gurney flap on NACA 0015 airfoil. A Navier-Stokes code. FLUENT, was used to calculate the flow field about the airfoil. The fully-turbulent results were obtained using the standard ${\kappa}-{\varepsilon}$ two-equation turbulence model. The numerical solutions showed the Gurney flap increased both lift and drag. These results suggested that the Gurney flap served to increase the effective camber of the airfoil. Gurney flap provided a significant increase in lift-to-drag ratio relatively at low angle of attack and for high lift coefficient. It turned out that 0.75% chord size of flap was best. The numerical results exhibited detailed flow structures at the trailing edge and provided a possible explanation for the increased aerodynamic performance.

• Journal of Industrial Technology
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• v.18
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• pp.335-341
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• 1998

A numerical investigation was performed to determine the effect of a Gurney flap on a NACA 23012 airfoil. A Navier-Stokes code, RAMPANT, was used to calculate the flow field about airfoil. The fully turbulent results were obtained using the standard $k-{\varepsilon}$ two-equation turbulence model. To provide a check case for our computational method, computations were performed for NACA 4412 airfoil which compared with Wedcock's experimental data. Gurney flap sizes of 0.5, 1.0, 1.5, and 2% of the airfoil chord were studied. The numerical solutions showed the Gurney flap increased both lift and drag. These results suggested that the Gurney flap served to increased the effective camber of the airfoil. But Gurney flap provided a significant increase in lift-to-drag ratio relatively at low angle of attack and for high lift coefficient. Also, it turned out that 0.5% chord size of flap was best one among them.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.650-655
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• 2016

In this study, a computational simulation of the internal flow characteristics was carried out for a Urea-SCR Injector. A single hole swirl injector with a swirl disk and slanted nozzle was used in this simulation. The maximum needle lift and opening velocity were selected as the design parameters. To analyze the unsteady internal flow characteristics of the Urea-SCR injector, the moving grid technique was applied to simulate the delicate needle movement. According to the simulation results, the injected mass flow rate from the Urea-SCR injector decreased with increasing needle opening velocity and maximum needle lift. This is because the Urea-solution tends to fill the empty space that the needle previously occupied. The swirl flow is decreased as the flow goes through the injector nozzle, because of the friction with the nozzle wall. Also, during the maximum needle lift period, the swirl coefficient and mean swirl coefficient increase with increasing needle lift. The results of this study may be used as the basic design data of related injectors.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.2
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• pp.277-286
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• 1989

Turbulent flows around two-dimensional vehicle-like bodies in ground proximity are numerically simulated. The Reynolds averaged Navier-Stokes equations with a k-.epsilon. turbulence model are numercally solved, and a body-fitted coordinate system is used. It is shown that the simulation is acceptable in comparison with limitted data measured in the wind-tunnel. According to numerical simulations, drag coefficients are under-estimated and lift coefficients are over-estimated during the model test in the wind-tunnel if the ground is fixed. Such ground effects are reduced as Reynolds number is increased. Reducing the gap between the vehicle and the ground make drag coefficients smaller and lift coefficients larger. The changes in static pressure distributions on the bottom and the rear surface play dominent roles in determination of the drag and the lift of the body in ground proximity. Drag component less than 10% of the total amount is contributed by skin-frictions. When the slant-angle of the body is reduced, the drag shows its minimum value and the lift shows its maximum value at about 22 degree.

• Tribology and Lubricants
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• v.39 no.5
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• pp.203-211
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• 2023

This study experimentally investigates the effects of angular acceleration on the friction and wear performances of a gas foil thrust bearing (GFTB) using a typical GFTB with six pads. The outer radius of the bearing is 31.5 mm, the total bearing area is 2,041 mm² , and the bump foil and incline (ramp) height are both 500 ㎛. The newly developed GFTB test rig for measuring the friction torque and coefficient measures the axial load, drag torque, lift-off speed, and touch-down speed. The experiment is conducted for angular accelerations of 78.5, 314.2, and 328.3 rad/s² at axial loads of 5, 10, and 15 N, respectively. The test shows that the start-up friction coefficient increases with increasing axial load at the same angular acceleration, and the friction coefficient decreases with increasing angular acceleration under the same axial load. As the angular acceleration increases, the lift-off speed at the motor start-up increases, and the touch-down speed at the motor stop decreases. The wear distance of the GFTB for a single on/off cycle increases with increasing axial load at the same angular acceleration and decreases nonlinearly with increasing angular acceleration under the same axial load. The test results suggest that adjusting the rotational angular acceleration helps reduce bearing friction and wear.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.12
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• pp.3135-3147
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• 1993

A numerical method is presented which can solve the steady flow and heat transfer from a rotating and heated circular cylinder in a uniform flow for a range of Reynolds number form 5 to 100. The steady response of the flow and heat transfer is simulated for various spin parameter. The effects on the flow field and heat transfer characteristics known as lift, drag and heat transfer coefficient are analyzed and the streamlines, velocity vectors, vorticity, temperature distributions around it were scrutinized numerically. As spin parameter increases the region of separation vortex becomes smaller than upper one and the lower region will vanish. The lift force, a large part is due to the pressure force, increases as the Reynolds number and it increases linearly as spin parameter increases. The pressure coefficient changes rapidly with spin parameter on the lower surface of the cylinder and the vorticity is sensitive to the spin parameter near separation region. As spin parameter increases the maximum heat coefficient and the thin thermal layer on front region are moved to direction of rotation. However, with balance between the local increase and decrease, the overal heat transfer coefficient is almost unaffected by rotation.