• 한국유체기계학회 논문집
• /
• 제14권2호
• /
• pp.29-34
• /
• 2011

Aerodynamic torque of wind turbine is highly nonlinear due to the nonlinear interactions between wind and blade. The aerodynamic nonlinearity is represented by nonlinear power and torque coefficients which are functions of wind speed, rotational speed of rotor, and pitch angle of blade. It is essential from the viewpoint of understanding and analysis of dynamic characteristics for wind turbine to linearize the aerodynamic torque and define aerodynamic nonlinear parameters as derivatives of aerodynamic torque with respect to the three parameters. In this paper, a linearization method of the aerodynamic torque from power coefficient is presented through differentiating it by the three parameters. And steady-state values of three aerodynamic nonlinear parameters according to wind speed are obtained and their nonlinear characteristics are investigated.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2004년도 춘계 학술대회논문집
• /
• pp.17-22
• /
• 2004

A space launch vehicle departs the ground in a low speed, soon reaches a transonic and a supersonic speed, and then flies in a hypersonic speed into the space. Therefore, the design of a launch vehicle should include the prediction of aerodynamic characteristics for all speed regimes, ranging from subsonic to hypersonic speed. Generally, Empirical and analytical methods and wind tunnel tests are used for the prediction of aerodynamic characteristics. This research presents considerable factors for aerodynamic analysis of a launch vehicle using CFD. This investigation was conducted to determine effects of wake over the base section on the aerodynamic characteristics of a launch vehicle and also performed to determine effects of the sting which exist to support wind tunnel test model.

• Wind and Structures
• /
• 제32권3호
• /
• pp.205-217
• /
• 2021

Cold regions with high air density and wind speed attract wind energy producers across the globe exhibiting its potential for wind exploitation. However, exposure of wind turbine blades to such cold conditions bring about devastating impacts like aerodynamic degradation, production loss and blade failures etc. A series of wind tunnel tests were performed to investigate the effect of icing on the aerodynamic properties of wind turbine blades. A baseline clean wing configuration along with four different ice accretion geometries were considered in this study. Aerodynamic force coefficients were obtained from the surface pressure measurements made over the test model using MPS4264 Simultaneous pressure scanner. 3D printed Ice templates featuring different ice geometries based on Icing Research Tunnel data is utilized. Aerodynamic characteristics of both the clean wing configuration and Ice accreted geometries were analysed over a wide range of angles of attack (α) ranging from 0° to 24° with an increment of 3° for three different Reynolds number in the order of 105. Results show a decrease in aerodynamic characteristics of the iced aerofoil when compared against the baseline clean wing configuration. The key flow field features such as point of separation, reattachment and formation of Laminar Separation Bubble (LSB) for different icing geometries and its influence on the aerodynamic characteristics are addressed. Additionally, attempts were made to understand the influence of Reynolds number on the iced-aerofoil aerodynamics.

• 한국전산유체공학회지
• /
• 제16권4호
• /
• pp.1-6
• /
• 2011

Aerodynamic characteristics depending on the shape of an internal motor in a small-size sirocco fan for residential ventilation have been investigated. For the aerodynamic analyses of the sirocco fan, three-dimensional Reynolds-averaged Navier-Stokes equations are solved with the shear stress transport model for turbulence closure. The flow analyses are performed on hexahedral grids using a finite-volume solver. The validation of the numerical results at steady-state is performed by comparing with experimental data for the pressure and efficiency. In order to investigate the aerodynamic characteristics depending on shape of an internal motor in a sirocco fan, the reference shape is analyzed compared to the case without internal motor. Additionally, two shape parameters, height and width of the internal motor in a sirocco fan, are tested to investigate their effects on the aerodynamic characteristics. The results show that the shape of the internal motor in a sirocco fan is an important factor to improve the aerodynamic performances.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2011년 춘계학술대회논문집
• /
• pp.321-326
• /
• 2011

Aerodynamic characteristics depending on the shape of an internal motor in a small-size sirocco fan for residential ventilation have been investigated For the aerodynamic analyses of the sirocco fan, three-dimensional Reynolds-averaged Navier-Stokes equations are solved with the shear stress transport model for turbulence closure. The flaw analyses are performed on hexahedral grids using a finite-volume solver. The validation of the numerical results at steady-state is performed by comparing with experimental data for the pressure and efficiency. In order to investigate the aerodynamic characteristics depending on shape of an internal motor in a sirocco fan, the reference shape is analyzed compared to the case without internal motor. Additionally, two shape parameters, height and width of the internal motor in a sirocco fan, are tested to investigate their effects on the aerodynamic characteristics. The results show that the shape of the internal motor in a sirocco fan is an important factor to improve the aerodynamic performances.

• 한국항공우주학회지
• /
• 제34권2호
• /
• pp.1-10
• /
• 2006

본 연구에서는 수치적 방법을 이용하여 타원형 익형의 공력특성에 대한 연구를 수행하였다. 타원형 익형의 경우 현재까지 널리 사용되어진 NACA 계열 익형들에 비하여 작은 앞전 곡률반경을 가진다. 또한 NACA 계열 익형들과는 달리 앞전과 같은 곡률반경을 가지는 뒷전 형상을 가지며, 익형의 최대 두께가 시위의 1/2지점에 존재한다. 타원형 익형의 경우 이러한 형상적인 특징들에 의하여 NACA 계열 익형들과는 다른 공력특성을 나타내는데, 본 연구에서는 같은 최대 두께를 가지는 NACA 계열 익형과 타원형 익형의 다양한 유동조건에서의 공력특성에 대한 수치해석 결과의 비교를 통하여 타원형 익형의 공력특성에 대하여 살펴보았다. 또한 타원형 익형의 두께변화에 따른 공력특성의 변화 역시 함께 고려하였다.

• Wind and Structures
• /
• 제17권2호
• /
• pp.163-184
• /
• 2013

An accurate identification of the aerodynamic characteristics of vehicles and the bridge is the premise for the coupled vibration analysis of a wind-vehicle-bridge system. At present, the interaction of aerodynamic forces between the road vehicles and bridge is ignored in most previous studies. In the present study, an experimental setup was developed to measure the aerodynamic characteristics of vehicles and the bridge for different cases in a wind tunnel considering the aerodynamic interference. The influence of the wind turbulence, the wind speed, the vehicle interference, and the vehicle position on the aerodynamic coefficients of vehicles, and the influence of vehicles on the static coefficients of the bridge were investigated, based on the experimental results. The variations in the aerodynamic characteristics of vehicles and the bridge were studied and the measured results were validated according to the results of surface pressure measurements on the vehicle and the bridge. The measured results were further validated by comparing the measured results with values derived numerically. The measured results showed that the wind turbulence, the vehicle interference, and the vehicle position significantly affected the aerodynamic coefficients of vehicles. However, the influence of the wind speed on the aerodynamic coefficients of the studied vehicle is small. The static coefficients of the bridge were also significantly influenced by the presence of vehicles.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 춘계학술대회
• /
• pp.1939-1944
• /
• 2004

Recently, several kinds of experimental and computational studies are being carried out to investigate the WIG aerodynamic characteristics which are of practical importance to develop the new ground transportation vehicle system. These works are mainly based upon conventional wind tunnel tests, but many problems associated with the WIG aerodynamic characteristics cannot be satisfactorily resolved due to the wind tunnel blockage effects or string problems to support the test object. To do this, it is necessary to develop a novel simulator appropriate to the WIG aerodynamics. The objective of the present study is to clarify the aerodynamic characteristics of a new developed WIG simulator, which is able to imitate real WIG flow circumstances such as gradually decelerating and accelerating flows.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2007년도 춘계 학술대회논문집
• /
• pp.79-82
• /
• 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.

• 한국군사과학기술학회지
• /
• 제14권3호
• /
• pp.397-404
• /
• 2011

The aerodynamic characteristics of a separated captive body in flow field around aircraft are studied to observe aerodynamic stability for safe separation from aircraft. Since the captive body separated from aircraft is initially exposed to unsteady flow pattern, the change of aerodynamic forces and moments should be measured to analyze how the flow pattern affects on the captive body at the vicinity of aircraft. Aerodynamic forces and moments of the separated captive body are measured at selected positions along predictable dropping trajectories. The measuring trajectories, generated by the free drop test of the dropping model in the wind tunnel, are consisted of 9 possible lines by free dropped trajectories. Experimental results show that the aerodynamic forces and moments are significantly varied with the distance between the captive body and aircraft. In conclusion, the change of aerodynamic characteristics within flow field around aircraft should be considered to simulate trajectories of the separated captive body from aircraft.