• Journal of Astronomy and Space Sciences
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• 제28권1호
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• pp.17-26
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• 2011

Bow shock, formed by the interaction between the solar wind and a planet, is generated in different patterns depending on the conditions of the planet. In the case of the earth, its own strong magnetic field plays a critical role in determining the position of the bow shock. However, in the case of Mars of which has very a small intrinsic magnetic field, the bow shock is formed by the direct interaction between the solar wind and the Martian ionosphere. It is known that the position of the Martian bow shock is affected by the mass loading-effect by which the supersonic solar wind velocity becomes subsonic as the heavy ions originating from the planet are loaded on the solar wind. We simulated the Martian magnetosphere depending on the changes of the density and velocity of the solar wind by using the three-dimensional magnetohydrodynamic model built by modifying the comet code that includes the mass loading effect. The Martian exosphere model of was employed as the Martian atmosphere model, and only the photoionization by the solar radiation was considered in the ionization process of the neutral atmosphere. In the simulation result under the normal solar wind conditions, the Martian bow shock position in the subsolar point direction was consistent with the result of the previous studies. The three-dimensional simulation results produced by varying the solar wind density and velocity were all included in the range of the Martian bow shock position observed by Mariner 4, Mars 2, 3, 5, and Phobos 2. Additionally, the simulation result also showed that the change of the solar wind density had a greater effect on the Martian bow shock position than the change of the solar wind velocity. Our result may be useful in analyzing the future observation data by Martian probes.

• Wind and Structures
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• 제12권3호
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• pp.281-283
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• 2009

Marquardt method is used to estimate the aerodynamic parameters in urban area of Beijing City, China, including displacement length (d), roughness length ($z_0$) and friction velocity (u*) and drag coefficient. The surface drag coefficient defined as the ratio between friction velocity and mean wind speed is 0.125 in our research, which is close to typical urban area value. The averaged d and $z_0$ are 1.2 m and 7.6 m. d and $z_0$ change with direction because of the surface heterogeneity over urban surface and reach their maximum values at S-SW sector, this tendency agrees with the surface rough element distribution around the observation tower.

• 한국항해항만학회지
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• 제32권8호
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• pp.597-602
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• 2008

실습선 한바다호는 수면 상부의 구조물이 상대적으로 큰 선형으로 풍압력의 영향을 크게 받아 압류나 회두와 같은 현상이 비교적 크게 나타나고, 특히 접이안 또는 항내에서 저속으로 운항할 경우 이러한 외력의 영향이 현저하게 작용한다. 본 논문에서는 파도가 충분히 발달되지 않은 항내 조선을 전제로 한바다호의 풍압력과 풍압모우멘트를 산출하여 상대 풍향과 풍속에 따른 표류각과 대응 타각을 분석하였다. 또한, 실습선 한바다호의 접이안시 예인선의 소요마력 결정을 선체에 작용하는 풍압력을 기초로 산출하였고, Bow Thruster를 이용한 접이안 가능 최대 풍속을 제시하였다. 연구 결과는 풍압력이 크게 작용하는 대형선의 항내조선과 예인선 운용에 큰 도움이 될 것으로 판단된다.

• Wind and Structures
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• 제38권4호
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• pp.295-307
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• 2024

The funnel-shaped vortex structure of tornadoes results in a spatiotemporally varying wind velocity (speed and direction) field. However, very limited full-scale tornado data along the height and radius positions are available to identify and reliably establish a description of complex vortex structure together with the resulting aerodynamic effects on the high-speed train (HST). In this study, the improved delayed detached eddy simulation (IDDES) for flow structures and aerodynamic pressures around an HST under tornado-like winds are conducted to provide high-fidelity computational fluid dynamics (CFD) results. To demonstrate the accuracy of the numerical method adopted in this study, both field observations and wind-tunnel data are utilized to respectively validate the simulated tornado flow fields and HST aerodynamics. Then, the flow structures and aerodynamic pressures (as well as aerodynamic forces and moments) around the HST at various locations within the tornado-like vortex are comprehensively compared to highlight the importance of considering the complex spatiotemporal wind features in the HST-tornado interactions.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.1575-1577
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• 2002

In this research we propose a method far rain rate estimation by using Doppler spectrum's data of wind profiler. The Doppler spectrum is used to calculate the wind velocity and wind direction. But in this research uses the parameters from Doppler spectrum, it calculates the rain rate. The rain rate estimation in this method will be compared to the obtained rain rate from the surface rain gauge. Two equipments are installed in the same area. The correlation coefficient between rain rate measuring method is 0.65.

• 한국전자통신학회논문지
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• 제18권6호
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• pp.1041-1048
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• 2023

윈드라이다와 윈드프로파일러는 연속적인 바람의 연직 분포를 고해상도의 자료로 산출하는 장비로써 최근 활용도가 높아지고 있다. 두 장비의 관측방식과 데이터 처리방식은 유사하지만, 기상 및 동작 설정에 따라 바람 탐지정확도의 차이가 발생할 수 있다. 두 장비의 특성과 바람 산출 방법을 소개하고 최신 장비 검증기준을 적용해 라디오존데로 관측한 바람과 비교하여 정확성을 평가한다. 이에 따라 장비도입에 따른 새로운 성능검증 방향과 추가로 필요한 보완점을 제시한다.

• Structural Engineering and Mechanics
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• 제72권5호
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• pp.541-555
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• 2019

Wind induced dynamic responses on hyperbolic cooling tower (HCT) shells are complicated functions of structure and wind properties, such as the fundamental frequency f_min, damping ratio ζ, wind velocity V, correlationship in meridian direction and so on, but comprehensions on the sensitivities of the dynamic responses to these four factors are still limited and disagree from each other. Following the dynamic calculation in time domain, features of dynamic effects were elaborated, focusing on the background and resonant components σ_B and σ_R, and their contributions to the total rms value σ_T. The σ_R is always less than σ_B when only the maximum σ_T along latitude is concerned and the contribution of σ_R to σ_T varies with responses and locations, but the σ_R couldn't be neglected for structural design. Then, parameters of the above four factors were artificially adjusted respectively and their influences on the gust responses were illustrated. The relationships of σ_R and the former three factors were expressed by fitted equations which shows certain differences from the existing equations. Moreover, a new strategy for wind tunnel tests aiming at surface pressures and the following dynamic calculations, which demands less experiment equipment, was proposed according to the influence from meridian correlationship.

• 대한공간정보학회지
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• 제18권2호
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• pp.107-112
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• 2010

풍력발전은 자연 상태의 무공해 에너지원이며 신재생에너지 중 가장 경제성이 높은 에너지원이다. 최근 소형 풍력 발전의 개발에 따라 단지나 초고층 건축물에도 풍력 발전 시설 설치가 가능해졌다. 이러한 지역에서의 효율적인 발전을 위해서는 적절한 입지 분석이 필요하다. 본 연구에서는 부산시를 대상으로 계층적 분석 기법을 이용하여 풍력 발전 시 요구되어지는 요인들의 상대적 가중치를 산정하고 부산시의 풍속과 풍향의 특징을 나타내었고 지형 공간정보체계를 이용하여 강서구, 기장군, 사하구 지역 내에서 녹산동, 철마면, 다대1동으로 후보지를 선정하였다.

• Wind and Structures
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• 제30권4호
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• pp.379-392
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• 2020

The paper presents a Life-Cycle Cost-based optimization framework for wind-excited tall buildings equipped with Tuned Mass Dampers (TMDs). The objective is to minimize the Life-Cycle Cost that comprises initial costs of the structure, the control system and costs related to repair, maintenance and downtime over the building's lifetime. The integrated optimization of structural sections and mass ratio of the TMDs is carried out, leading to a set of Pareto optimal solutions. The main advantage of the proposed methodology is that, differently from the traditional optimal design approach, it allows to perform the unified design of both the structure and the control system in a Life Cycle Cost Analysis framework. The procedure quantifies wind-induced losses, related to structural and nonstructural damage, considering the stochastic nature of the loads (wind velocity and direction), the specificity of the structural modeling (e.g., non-shear-type vibration modes and torsional effects) and the presence of the TMDs. Both serviceability and ultimate limit states related to the structure and the TMDs' damage are adopted for the computation of repair costs. The application to a case study tall building allows to demonstrate the efficiency of the procedure for the integrated design of the structure and the control system.

• 한국가시화정보학회지
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• 제14권3호
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• pp.28-31
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• 2016

In this study, we investigate the wake characteristics in two cases which are laminar inflow and turbulent inflow. To solve the flow with wind turbines and its wake, we use large eddy simulation (LES) technique with actuator line method (ALM) and turbulent inflow of Turbsim. Turbulent inflow which contains the characteristic of the stable atmospheric boundary layer is used. We perform the quantitative analysis of velocity deficit and turbulence intensity in two cases. Time series of velocity deficit at the first, the second column in two cases are compared to observe the performance of wind turbine. The performance in the first column in laminar inflow is overestimated compared to that in turbulent inflow. And we observe that wake in the case with turbulent inflow drive to the span-wise direction and wake recovery in turbulent inflow is more effective. In quadrant analysis of Reynolds stress, the ejection and the sweep motion in turbulent inflow case are bigger than those in laminar inflow case.