• Wind and Structures
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• 제24권2호
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• pp.145-169
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• 2017

The auxiliary structures of a high-rise building, such as balconies, ribs, and grids, are usually much smaller than the whole building; therefore, it is difficult to simulate them on a scaled model during wind tunnel tests, and they are often ignored. However, they may have notable effects on the local or overall wind loads of the building. In the present study, a series of wind pressure wind tunnel tests and high-frequency force balance (HFFB) wind tunnel tests were conducted on rigid models of an actual super high-rise building with vertical ribs protruding from its facades. The effects of the depth and spacing of vertical ribs on the mean values, fluctuating values and the most unfavorable values of the local wind pressure coefficients were investigated by analyzing the distribution of wind pressure coefficients on the facades and the variations of the wind pressure coefficients at the cross section at 2/3 of the building height versus wind direction angle. In addition, the effects of the depth and spacing of vertical ribs on the mean values, fluctuating values and power spectra of the overall aerodynamic force coefficients were studied by analyzing the aerodynamic base moment coefficients. The results show that vertical ribs significantly decrease the most unfavorable suction coefficients in the corner recession regions and edge regions of facades and increase the mean and fluctuating along-wind overall aerodynamic forces.

• 신재생에너지
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• 제18권3호
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• pp.60-71
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• 2022

A wind tunnel provides artificial airflow around a model throughout the test section for investigating aerodynamic loads. It has various applications, which include demonstration of aerodynamic loads in the building, automobile, wind energy, and aircraft industries. However, owing to the high equipment costs and space-requirements of wind tunnels, it is challenging for numerous studies to utilize a wind tunnel. Therefore, a digital wind tunnel can be utilized as an alternative for experimental research because it occupies a significantly smaller space and is easily operable. In this study, we performed airfoil testing based on velocity field measurements utilizing a digital wind tunnel. This wind tunnel can potentially be utilized to test the full-range aerodynamic characteristics of airfoils.

• Wind and Structures
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• 제20권3호
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• pp.449-468
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• 2015

Current wind-resistance designs of large-scale indirect dry cooling towers (IDCTs) exclude an important factor: the influence of the ventilation rate for radiator shutter on wind loads on the outer surfaces of the tower shell. More seemingly overlooked aspects are the effects of various ventilation rates on the wind pressure distribution on the tower surfaces of two IDCTs, and the feature of the flow field around them. In order to investigate the effects of the radiator shutter ventilation rates on the aerodynamic interference between IDCTs, this paper established the numerical wind tunnel model based on the Computational Fluid Dynamic (CFD) technology, and analyzed the influences of various radiator shutter ventilation rates on the aerodynamic loads acting upon a single and two extra-large IDCTs during building, installation, and operation stages. Through the comparison with the results of physical wind tunnel test and different design codes, the results indicated that: the influence of the ventilation rate on the flow field and shape coefficients on the outer surface of a single IDCT is weak, and the curve of mean shape coefficients is close to the reference curve provided by the current design code. In a two-tower combination, the ventilation rate significantly affects the downwind surface of the front tower and the upwind surface of the back tower, and the larger positive pressure shifts down along the upwind surface of the back tower as the ventilation rate increases. The ventilation rate significantly influences the drag force coefficient of the back tower in a two-tower combination, the drag force coefficient increases with the ventilation rate and reaches the maximum in a building status of full ventilation, and the maximum drag coefficient is 11% greater than that with complete closure.

• Wind and Structures
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• 제11권2호
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• pp.97-120
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• 2008

Wind and wave loadings have a predominant role in the design of offshore structures in general, and articulated tower in particular for a successful service and survival during normal and extreme environmental conditions. Such towers are very sensitive to the dynamic effects of wind and wind generated waves. The exposed superstructure is subjected to aerodynamic loads while the submerged substructure is subjected to hydrodynamic loads. Articulated towers are designed such that their fundamental frequency is well below the wave frequency to avoid dynamic amplification. Dynamic interaction of these towers with environmental loads (wind, waves and currents) acts to impart a lesser overall shear and overturning moment due to compliance to such forces. This compliancy introduces geometric nonlinearity due to large displacements, which becomes an important consideration in the analysis of articulated towers. Prediction of the nonlinear behaviour of these towers in the harsh ocean environment is difficult. However, simplified realistic mathematical models are employed to gain an important insight into the problem and to explore the dynamic behaviour. In this paper, various modeling approaches and solution methods for articulated towers adopted by past researchers are reviewed. Besides, reliability of articulation system, the paper also discussed the design, installation and performance of articulated towers around the world oceans.

• 한국항공운항학회지
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• 제19권4호
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• pp.67-73
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• 2011

For loads analysis of airplane, applicable regulation should be determined. Then, loads conditions are prepared from the regulation. Modeling for aerodynamic, mass, and structure are performed. Panel method is usually adopted for aircraft loads analysis to obtain air loads. The ARGON which is a multidisciplinary fixed wing aircraft design software co-developed by the KARI and TsAGI are used for loads analysis. The ARGON can be utilized for flutter and stress analysis as well as for flight and ground loads analysis. In this paper, flight loads analysis for wing structural design of the regional aircraft at the conceptual design phase are performed with the ARGON. FAR 25 is used for the regulation for the load analysis. Shear force, bending moment and torsion diagrams for the wing and shear force and hinge moment for the aileron are presented.

• 풍력에너지저널
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• 제5권1호
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• pp.43-49
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• 2014

Primarily, tower loads of a wind turbine arise from aerodynamic effect and a top head mass. But sometime asymmetric loads of rotor also affect on the tower loads. Especially ice formation on two blades out of three causes the asymmetric loads, because the ice formation on blades lead to large rotating mass imbalance. This rotating mass imbalance of rotor affects tower fatigue loads. So design load cases of ice formation on blade should be considered in the fatigue design loads of the tower according to GL guideline 2010. This paper describes the change of tower fatigue loads following increase of tower height in the condition of ice formation. Finally, the optimal operation strategy is examined in order to reduce tower fatigue design loads.

• Journal of Astronomy and Space Sciences
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• 제1권1호
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• pp.5-21
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• 1984

The airflow along the surface of a launch vehicle together with base flow of clustered nozzles cause problems which may affect the stability or efficiency of the entire vehicle. The problem may occur when the vehicle is on the launching pad or even during flight. As for such problems, local steady-state loads, overall steady-state loads, buffet, ground wind loads, base heating and rocket-nozzle hinge moments are examined here specifically.

• 한국항공우주학회지
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• 제43권12호
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• pp.1071-1078
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• 2015

외부형 핀틀추력기의 핀틀 행정거리, 고도, 보어유무가 핀틀추력기 성능에 미치는 영향에 대해서 전산수치해석을 수행하였다. 유동은 핀틀 행정거리에 관계없이 항상 과소팽창하는 결과를 보였다. 핀틀추력기의 주요 성능 지표 중 추력조절측면에서는 우수한 성능을 보였지만, 핀틀 지지대 윗면에서 발생한 충격파로 인해 공력하중이 증가하였다. 지상에서 고도 20 km로 상승하면 노즐 출구 속도, 마하수, 추력 등이 증가하였으며, 공력하중 또한 증가하였다. 보어의 존재는 공력하중을 5.9% 증가시켜 핀틀의 구동력을 위해서는 보어가 없는 형상이 유리하다고 판단된다.

• Wind and Structures
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• 제20권2호
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• pp.249-274
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• 2015

Long-span cable-stayed bridges exhibit some features which are more critical than typical long span bridges such as geometric and aerodynamic nonlinearities, higher probability of the presence of multiple vehicles on the bridge, and more significant influence of wind loads acting on the ultra high pylon and super long cables. A three-dimensional nonlinear fully-coupled analytical model is developed in this study to improve the dynamic performance prediction of long cable-stayed bridges under combined traffic and wind loads. The modified spectral representation method is introduced to simulate the fluctuating wind field of all the components of the whole bridge simultaneously with high accuracy and efficiency. Then, the aerostatic and aerodynamic wind forces acting on the whole bridge including the bridge deck, pylon, cables and even piers are all derived. The cellular automation method is applied to simulate the stochastic traffic flow which can reflect the real traffic properties on the long span bridge such as lane changing, acceleration, or deceleration. The dynamic interaction between vehicles and the bridge depends on both the geometrical and mechanical relationships between the wheels of vehicles and the contact points on the bridge deck. Nonlinear properties such as geometric nonlinearity and aerodynamic nonlinearity are fully considered. The equations of motion of the coupled wind-traffic-bridge system are derived and solved with a nonlinear separate iteration method which can considerably improve the calculation efficiency. A long cable-stayed bridge, Sutong Bridge across the Yangze River in China, is selected as a numerical example to demonstrate the dynamic interaction of the coupled system. The influences of the whole bridge wind field as well as the geometric and aerodynamic nonlinearities on the responses of the wind-traffic-bridge system are discussed.

• 한국군사과학기술학회지
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• 제25권1호
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• pp.9-22
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• 2022

A fighter performing a reconnaissance mission is equipped with a pod that drives optical/infrared sensors for acquiring and identifying target information on the lower part of the fuselage. Due to the nature of the reconnaissance mission, the fighter performs high speed evasive maneuvers, and the resulting load should be considered importantly for the development of the pod. This paper concerns a numerical investigation into the inertial and aerodynamic loads of the airborne pod of high performance aircrafts. For the aerodynamic load analysis, the pylon and pod shapes are added to the fighter 3D model, and the commercial software was used for static and dynamic analysis. Considering the practical mission conditions, the common/extreme conditions were established respectively in the static and dynamic situations of pods and the driving torque could be tripled under dynamic conditions. In the analysis of inertia load, a 3-DOF model considering roll and turning maneuvers was derived by the Lagrangian method, and then the numerical integration method was applied to the analysis. As a results, it was conformed that the inertia load was generally induced at a low level compared to the aerodynamic load, but depending on the unbalance mass condition of the pod, the inertia load cannot be negligible.