• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.10
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• pp.833-844
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• 2018

This paper aims to predict the aerodynamic characteristics of individual rotor for the gust and flight conditions. Transformation procedure into the wind frame is conducted to analyze the gust. Hover, forward, and climb flight conditions of an individual rotor are analyzed using the blade element momentum theory (BEMT) considering the rigid blade flapping motion. XFOIL is used to derive aerodynamic results. Validation for hover, forward flight, and climb conditions are conducted using the present BEMT. In addition, a static experimental environment is constructed. The experimental results and the present BEMT are compared and verified.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.5
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• pp.1-11
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• 2006

The effects of continuous blowing on flow control and stall suppression for flows over a NACA 0015 airfoil at low Reynolds numbers were numerically investigated through its parameter variation on unstructured meshes. The aerodynamic force and moment variations due to flow control were examined, along with the stall angle-of-attack change for stall suppression. The results showed that blowing with relatively strong jet increases lift at the cost of drag increment below stall angle. Continuous blowing delays flow stall when it is implemented near the leading edge. When the blowing jet was aligned along the flow direction on the airfoil, the favorable flow control effect was most significant below the stall angle of attack.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.3
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• pp.211-219
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• 2008

A three-dimensional inviscid flow solver has been developed based on unstructured meshes for the investigation of the effect of the external stores on the tail surfaces of a generic fighter aircraft. The numerical method is based on a vertex-centered finite-volume discretization and an implicit point Gauss-Seidel time integration. The calculations were made for a steady flow and the computed results were compared with experimental data to validate the flow solver. An unsteady time-accurate computation of the generic fighter aircraft with external stores at transonic flight conditions showed that the external stores cause unsteady loading on the horizontal tail surface due to the mutual interference between their wake and the horizontal tail surface. It was shown that downward deflection of the trailing edge flap significantly reduces the undesirable interference effect.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.4
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• pp.289-309
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• 2014

A rotor blade is an important device that converts kinetic energy of wind into mechanical energy. Rotor blades affect the power performance, energy conversion efficiency, and loading and dynamic stability of wind turbines. Therefore, considering the characteristics of a wind turbine system is important for achieving optimal blade design. This study examined the general blade design procedure for a wind turbine system and aero-structure design results for a 2-MW class wind turbine blade (KR40.1b). As suggested above, a rotor blade cannot be designed independently, because its ultimate and fatigue loads are highly dependent on system operating conditions. Thus, a reference 2-MW wind turbine system was also developed for the system integrated load calculations. All calculations were performed in accordance with IEC 61400-1 and the KR guidelines for wind turbines.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.12
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• pp.1161-1169
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• 2012

A numerical study has been conducted to investigate the aerodynamic characteristics and behavior of a wing-tip vortex around a three-dimensional symmetric wing (NACA0015) in the vicinity of the ground. The aerodynamic characteristics and the wing-tip vortex change as a wing approaches the ground as a result of two different phenomena: the ground effect and the Venturi effect. The ground effect increases lift and decreases drag whereas the Venturi effect generates negative lift and increases drag suddenly. A symmetric airfoil experiences both phenomena with respect to changes in the angle of attack. In the case of a NACA0015 airfoil, the Venturi effect is dominant at small angles of attack but the ground effect is dominant at large angles of attack. Interestingly, both phenomena can be observed at the 4 degree of angle of attack. The vortex core moves inside a wing when the wing experiences the Venturi effect, whereas the vortex core moves outward when the wing experiences the ground effect.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.6
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• pp.537-543
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• 2016

A new approach to systematically model aerodynamic coefficients using an adaptive sampling based wind tunnel testing considering cost is proposed. The Latin Hypercube design is used for selecting initial test points. The Gaussian Process (GP) is iteratively used during the experiment to determine additional experimental points that minimizes the uncertainty reduction per incremental cost. A numerical simulation based experiment was conducted using the static aerodynamic coefficient database a fighter aircraft, which demonstrated the validity of the proposed method.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.7
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• pp.529-537
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• 2021

Wind tunnel tests were carried out with a scramjet high speed vehicle. Since the scramjet engine does not have a compressor, it has a simple structure, but it is important to design the intake for the supersonic combustion in the combustion chamber. In this study, internal flow characteristics and the starting condition were analyzed by measuring the pressure at the isolator exit just before the combustion chamber, and the intake performance parameters were calculated and compared the result on every Mach number. The aerodynamic characteristics of the flow-through high speed vehicle were analyzed and internal drag correction is required to precisely analyze the aerodynamic characteristics. In this paper, an experimental technique using three probes for internal drag correction was proposed. By applying internal drag correction, it was able to figure out the effect of the internal flow on the aerodynamic force of the vehicle.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.8
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• pp.64-71
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• 2004

A computational study on the supersonic flow around the lateral jet controlled missile has been performed. For this purpose a three dimensional Navier-Stokes computer code(AADL3D) has been developed and case studies have been performed by comparing the normal force coefficient and the moment coefficient of a missile body for different jet flow conditions including jet pressure and jet Mach number. The results show different behavior of normal force and moment variation according to jet pressure variation and jet Mach number variation. From the detailed flow field analyses, it is verified that most of the normal force loss and the pitching moment generation are taken place at the low-pressure region behind the jet nozzle. Furthermore, it is shown that the pitching moment can be efficiently reduced by obtaining the lateral thrust through higher jet Mach number rather than through high jet pressure.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.9
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• pp.27-34
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• 2004

A computational study on the supersonic flow around the lateral jet controlled missile has been performed. For this purpose a three dimensional Navier-Stokes computer code(AADL3D) has been developed and case studies have been performed by comparing the normal force coefficient and the moment coefficient of a missile body for several parameters such as angles of attack, circumferential jet positions, and spouting jet angles. Missile surface is divided into four regions with respect to the center of gravity, and the normal force and moment distribution at each region are compared. The results show different behavior of the normal force and moment variation according to each parameter. Furthermore, it is shown that the pitching moment can be minimized through proper combination of each parameter.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.3
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• pp.177-182
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• 2007

The effects of three fuselage head shapes and nonplanar ground surface on the aerodynamic characteristics of FAST fuselages are investigated using a boundary element method. Wind tunnel test is also performed to validate the present method and to identify the wall effect on the frictional drag which cannot be analyzed using the present method. It is found that the channel has an effect of increasing the lift of those investigated fuselages. The optimal head shape depends on the design conditions of the FAST and its guideway channel. Comparing the calculated induced drag with the measured total drag, it can be concluded that the profile drag is independent of the ground height. Thus, the present numerical method can be applied to the conceptual design of the high-speed ground transporters if only the profile drag of the vehicle in free flight is assumed to be known.