• Journal of Institute of Control, Robotics and Systems
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• v.15 no.12
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• pp.1157-1162
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• 2009

The aerodynamic torque and power caused by the interaction between the wind and blade of wind turbine are highly nonlinear. For this reason, the overall dynamic behaviors of wind turbine have nonlinear characteristics. The aerodynamic nonlinearity also affects properties of torque control for wind turbine. In this paper, the nonlinear aerodynamic property according to the wind speed below rated power and its effects on the torque control system are investigated. Nonlinear parameter representing change of aerodynamic torque with respect to rotor speed is obtained by linearization technique. Effects of this aerodynamic nonlinear parameter on the closed-loop torque system with PI controller for an 1.5 MW wind turbine are presented.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.43-49
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• 2010

Aerodynamic design of the vane type multi-function probe was tried by using CFD and wind tunnel test for the MALE UAV and small business jets. The present multi-function probe can measure total pressure, static pressure and angle of attack by using rotating vane. Therefore major performances are determined by aerodynamic characteristics of vane. In oder to design the sensor compatible to the requirement, aerodynamic characteristics of sensors was investigated by using CFD and dynamic response analysis was also performed for trasient performance. The final aerodynamic performance was measured by the wind tunnel test at Aeorsonic and the results successfully used for the design of vane type multi-function air data sensor.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.561-564
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• 2002

For the reduction of fuel consumption of high speed, the aerodynamic drag must be reduced. In early vehicle design process, it is very important to have information about aerodynamic characteristics of design models. In this phase CFD methods are usually used to predict the aerodynamic forces. But commercial programs using turbulence models cannot give a good agreement with experimental result and have also problems with convergence. PowerFLOW employs a new technology called DIGITAL PHYSICS, which provides a different approach to simulating fluids. DIGITAL PHYSICS uses a lattice-based approach (extended from lattice-gas and lattice-Boltzmann methods) where time, space and velocity are discrete. This discrete system represents the Wavier-Stokes continuum behavior without the numerical instability Issues of traditional CFD solvers, such as convergence. In this paper, aerodynamic performance of vehicles are simulated using PowerFLOW by Exa and results are compared with experimental wind tunnel data.

• Wind and Structures
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• v.12 no.3
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• pp.205-217
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• 2009

Aerodynamic flutter control for long-span cable-supported bridges was investigated based on three basic girder sections, i.e. streamlined box girder section, box girder section with cantilevered slabs and two-isolated-girder section. Totally four kinds of aerodynamic flutter control measures (adding fairings, central-slotting, adding central stabilizers and adjusting the position of inspection rail) were included in this research. Their flutter control effects on different basic girder sections were evaluated by sectional model or aeroelastic model wind tunnel tests. It is found that all basic girder sections can get aerodynamically more stabled with appropriate aerodynamic flutter control measures, while the control effects are influenced by the details of control measures and girder section configurations. The control effects of the combinations of these four kinds of aerodynamic flutter control measures, such as central-slotting plus central-stabilizer, were also investigated through sectional model wind tunnel tests, summarized and compared to the flutter control effect of single measure respectively.

• Journal of Aerospace System Engineering
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• v.10 no.1
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• pp.29-34
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• 2016

Flutter wind-tunnel test is an expensive and complicated process. Also, the test model may has discrepancy in the structural characteristics when compared to those of the real model. "Dry Wind-Tunnel" (DWT) is an innovative testing system which consists of the ground vibration test (GVT) hardware system and software which computationally can be operated and feedback in real-time to yield rapidly the unsteady aerodynamic forces. In this paper, we study on the aerodynamic forces of DWT system to feedback in time domain. The aerodynamic forces in the reduced-frequency domain are approximated by Minimum-state approximation. And we present a state-space equation of the aerodynamic forces. With the two simulation model, we compare the results of the flutter analysis.

• Phonetics and Speech Sciences
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• v.8 no.3
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• pp.39-49
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• 2016

The present study examined the change of aerodynamic features after laryngomicrosurgery in patients with vocal polyps. Aerodynamic evaluation was performed in thirty-nine patients (15 males and 24 females) one week before surgery and four weeks after surgery. Evaluation protocols of vital capacity, maximum sustained phonation(MXPH), and voicing efficiency(VOFT) were used to collect 29 phonatory aerodynamic measures, requiring voice with a comfortable pitch and loudness. Statistically significant changes were found for phonation time and airflow values in the MXPH protocol, while changes were also found for airflow values, subglottal pressure values and acoustic resistance values in the VOFT protocol. Although phonation time was increased in both male and female patients, gender-dependent changes were found in airflow measurements. Men's phonation time increased with no difference in airflow rate, but women's phonation time increased with decreased airflow rate and lower subglottal pressure. The changes of aerodynamic features may be affected by women's self-perceived change for vocal attitude, which was reducing sense of vocal effort after surgery.

• 한국전산유체공학회:학술대회논문집
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• 2007.04a
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• pp.79-82
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• 2007

The aerodynamic coefficients of Apollo capsule are calculated using a DSMC solver, SMILE, and the results agree very well with the data predicted by NASA. The aerodynamic characteristics of an orbital block which operates at high altitudes in the free molecule regime are also predicted. For the nominal flow conditions, the predicted aerodynamic force is very small since the dynamic pressure is extremely low. And the additional aerodynamic coefficients for the analysis of the attitude control are presented as the angle of attack and the side slip angle vary from $+45^{\circ}\;to\;-45^{\circ}$ of the nominal angle.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.3
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• pp.31-39
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• 1996

The effect of rear-spoiler attached at rear end of automobile trunk on the aerodynamic characteristics of a MIRA reference car model was experimentally investigated. For different shapes and positions(G/H) of the rear-spoiler, the aerodynamic forces on the automobile were measured at various flow speed(ReL). The effect of rear-spoiler on the wake structure behind the automobile was also investigated using flow visualization and hot-wire anemometer. The rear-spoiler modifies the near wake structure and decreases aerodynamic drag and increases driving stability compared with those of the conventional automobile without rear-spoiler. From the experimental results, rear-spoiler of airfoil shape installed at the position of G/H=0.084 shows the best aerodynamic performance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.447-453
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• 2012

Nowadays, high speed train has settled down as a fast and convenient environment-friendly transportation and it's need is gradually increasing. However increased train speed leads to increased aerodynamic noise, which causes critically affects comfortability of passengers. Especially, the pantograph of high speed train is protruded out of train body, which is the main factor for increased aerodynamic noise. In this research, to reduce aerodynamic noise pantograph, panhead's shape changed to aerodynamical shape. aerodynamic noise of pantograph is predicted by CFD (Computational Fluid Dynamic) and FW-H (Ffowcs Williams-Hawkings) equation. Also, the sound pressure level of aerodynamic noise of base and modified models are predicted. And the reduction effects of the sound pressure level is analyzed.

• International Journal of Aeronautical and Space Sciences
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• v.7 no.1
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• pp.43-53
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• 2006

Aerodynamic shape design of the Mid-sized Aerostat was performed with computational fluid dynamics. Design procedure included determination of hull volume and length, hull shape, tailfin configuration with anhedral and location, tailfin section. For aerodynamic analysis, three dimensional Navier-Stokes equations were applied with Spalart-Allmaras turbulence model. During design procedure, static moment derivatives were mainly considered for the stability of aerostat and structural limitations were also considered for practical application of the designed shape. Aerodynamic analysis of the designed aerostat was carried out and aerodynamic characteristics were compared with those of the TCOM 71m aerostat, one of the most successful commercial aerostats. It was found that the designed KARI Mid-sized Aerostat had better stability characteristics compared to the TCOM 71m aerostat.