• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.45 no.10
• /
• pp.817-824
• /
• 2017

This paper presents the characteristics of wing-tail interference for a tail-controlled missile. The magnitude of wing-tail interference was calculated with wind tunnel test results and its effects on aerodynamic coefficients were investigated. The downwash angle of tail wing was calculated with experimental data and the effect of wing-tail interference was expressed as a ratio of angle of attack. Numerical simulations were made to examine flow characteristics of wing-tail interference and the vorticity contour of missile were compared with respect to angle of attack. Experimental and numerical analysis results show that the wing-tail interference has significant effects on static stability of tail-controlled missile.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.1 s.173
• /
• pp.126-133
• /
• 2000

Noise of automotive alternators can be classified into mechanical noise, aerodynamic noise and electro-magnetic noise. which is the same as for electric motors. Previous studies show that the elect ro-magnetic noise takes a maw peak at the rotating frequency multiplied by the number of stator slots. It has not been proved clearly so far, however, that the major peak is wholely due to the stator slots. On the contrary it is well known that noise of motors. which has a mechanism similar to the alternator except that the number of stator slots in automotive alternators is in gene\integer multiple of that of rotor segments, is closely related to the number of rotor slots. Therefore, the statement that only the stator slots is the source of the major peak in the noise spectrum of alternators is suspicious although not easy, to show theoretically, that the statement is incorrect. In this paper. effects of the stator slots on the noise in an automotive alternator are experimentally investigated by intentionally modifying the number of stator slots in such a way that the number of the states is not an integer multiples of the rotor slots. It is shown that both the stator slots are not so much influential as the rotor slots and claimed that the major peak in the noise spectrum of conventional alternators is due to superposition of a component caused by the stator and a higher harmonic component caused by the rotor

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.43 no.7
• /
• pp.601-608
• /
• 2015

The static aeroelastic analysis and optimization of flexible wings are conducted for steady state conditions while both aerodynamic and structural parameters can be used as optimization variables. The system of multidisciplinary design optimization as a robust methodology to couple commercial codes for a static aeroelastic optimization purpose to yield a convenient adaptation to engineering applications is developed. Aspect ratio, taper ratio, sweepback angle are chosen as optimization variables and the skin thickness of the wing. The real-coded adaptive range multi-objective genetic algorithm code, which represents the global multi-objective optimization algorithm, was used to control the optimization process. The support vector regression(SVR) is applied for optimization, in order to reduce the time of computation. For this multi-objective design optimization problem, numerical results show that several useful Pareto optimal designs exist for the flexible wing.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.41 no.7
• /
• pp.516-523
• /
• 2013

The tip clearance effect on counter-rotating ducted fan of VTOL UAV in hovering condition, was investigate using computational analysis. The $k-{\omega}$ SST turbulence model is employed in this study. The numerical results of baseline model are validated by wind tunnel test in hovering and forward conditions. It is observed that if tip clearance of one rotor in the counter-rotating ducted fan increase then the thrust coefficient of another rotor increases. In Addition to this, when the tip clearance of the rear rotor increases, the thrust of the ducted fan is improved due to increasing of average total pressure at exit plane.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.41 no.7
• /
• pp.552-560
• /
• 2013

Airplane Buhwal is the first light airplane which is designed and made in South Korea. Restoration of airplane Buhwal is designed based on the one made by Korean Airforce in 2004 but there are some changes also. It uses aluminum main wing, electronic indicator, BRS(Ballistic recovery parachute) and black box for improved performance. In this paper, for the restorated Buhwal, major design changes are introduced, structure, aerodynamic and stability analysis are reviewed and improved performances which is proven through flight test are shown. This study will be a big help for domestic light airplane development.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.46 no.7
• /
• pp.527-534
• /
• 2018

The endurance of the multi-copter is one of the important variables that determine the mission performance. Therefore, accurate endurance should be defined as essential for performing effective missions. In this paper, we present the results of the study on the flight performance of the aircraft, especially the hovering of the drone(multi-copter). Unlike conventional aircraft, which consider aerodynamic performance by the fuselage, the multi-copter is mostly determined by the propulsion system. Therefore, the research method classifies the various parts constituting the drone system into functions, analyzes the performance of the unit parts and obtains the experimental data by sorting out the specifications and functions at the component level and mathematical formulation, The results of this study are as follows. In addition, the 5kg class quad copter was used to predict and verify the voltage change with endurance through analysis of in situ flight. By predicting endurance under various conditions, it can help design/build the right Multi-copter for mission.

• Composites Research
• /
• v.13 no.2
• /
• pp.61-71
• /
• 2000

Today, the use of composite materials become an essential part in the design and manufacturing process of the flight vehicles to reduce the structural weight. Since the structural properties can be varied largely due to the stacking sequence of ply angles, it is very important problem to determine the optimized ply angles under a design objective. Thus, in this study, the analysis of static aeroelastic optimization of a composite wing has been performed. An analytical system to calculate and optimize tile aero-structural equilibrium position has been developed and incorporated with the genetic algorithm. The effects of stacking sequence on the structural deformation and aerodynamic distribution have been studied and calculated with the condition of minimum structural deformation for a swept-back composite wing. For the set of practical stacking angles, the design results to maximize the performance of static aeroelasticity are also presented.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.3
• /
• pp.269-274
• /
• 2014

In this study, low noise designs for a Savonius wind turbine were numerically investigated. As was reported in our previous study, the harmonic components with a fundamental frequency higher than the BPF were identified as being dominant in the noise spectrum of a Savonius wind turbine, and these components were a result of vortex shedding. On a basis of this observation, an S-shaped blade tip is proposed as a means of reducing the noise generated by small vertical(Savonius) wind turbines. This blade induces phase differences in the shedding vortices from the blades, and thus reduces the noise from the wind turbine. The aerodynamic noise characteristics of the conventional and "S-shaped" Savonius turbines were investigated by using the Hybrid CAA method where the flow field around the turbine is computed using the CFD techniques and the radiated noise are predicted by applying acoustic analogy to the computed flow field data. The degree of noise reduction resulting from the proposed design and its reduction mechanism were confirmed by comparing the predicted noise spectrum of these turbines and the flow characteristics around them.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.04a
• /
• pp.466-471
• /
• 2014

The interior vehicle noise due to the exterior aerodynamic field is an important topic in the acoustic design of a car. The air flow detached from the A-pillar and impacting the side windows are of particular interest as they are located close to the driver / passenger and provides a lower insulation index than the trimmed car body parts. This paper presents a numerical analysis method for a simplified vehicle model. The internal air cavity including trim component are included in the simulation. The car body includes the windshield and two side windows. The body is made of aluminum and trimmed with porous layers. The methodology proposed in this paper relies on two steps: the first step involves the computation of the exterior flow and turbulence induced non-linear acoustic field using PowerFlow. The second step consists in the computation of the vibro-acoustic transmission through the window using the finite element vibro-acoustic solver Actran. Additionally in order to validate the numerical process, an experimental set-up has been created based on the simplified vehicle. The vibration of the windshield and windows, the total wind noise level results and the relative contributions of the different windows are then presented and compared to measurements. The influence of the flow yaw angle (different wind orientation) is also assessed.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.31 no.2
• /
• pp.17-24
• /
• 2003

This paper presents results from steady wind tunnel test conducted on a $65^{\circ}$ delta wing at a root chord Reynolds number of $1.76{\times}10^6$. In these experiments, the wing was instrumented with 188 pressure taps, conjunction with powerful multi-channel data logging system, allowed the wing upper surface pressure distribution to be measured. Analysis indicates that the wing upper surface distribution can provide considerable insight into the comvined aerodynamic effects of angle of attack and sideslip on the wing. In a sideslip condition, the strength of the vortex on the windward side is much stronger than that of leeward side. This asymmetric pressure disstribution betwwen each side of wings result in a negative value of rolling moment. However, at a certatin range of angle of attck and sideslip angle(${\alpha}$=$24^{\circ}{\sim}36^{\circ}C$, ${\beta}$=$-5^{\circ}{\sim}-15^{\circ}C$) abrupt change of sign of rolling monent, rolling monent reversal, was observed.