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基于共轭方程法的跨音速机翼气动力优化设计 总被引:6,自引:5,他引:6
设计状态的机翼气动力特性是设计人员最为关心的指标, 应用控制理论设计方法进行了有升力约束情形下跨音速机翼阻力优化设计研究, 根据给定的目标函数推导了相应的共轭方程和边界条件, 研究了共轭方程的数值求解方法, 以及计算目标函数对设计变量的敏感性导数时所涉及的度量矩阵变分求解问题, 研究了流场计算、共轭方程数值求解、敏感性导数求解和拟牛顿优化算法这几个主要方面的有效结合问题, 发展出了一种跨音速机翼气动力优化设计方法, 进行了跨音速机翼气动力优化设计研究验证, 优化后机翼气动力特性有一定程度的改善, 阻力系数能减少20%左右, 而升力系数有所增大, 说明所发展的设计方法是成功的, 该设计方法在跨音速及复杂外形气动设计方面比以往设计方法具有更好的适用性和优越性。 相似文献
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D. E. Page M. Pick L. Kresák G. C. M. Reijnen A. G. W. Cameron Cornelius J. E. Schuurmans Mikhail Ya Marov B. Goldberg T. R. Kaiser J. Lemaire L. Sehnal H. Elsässer B. Valniček W. de Graaff Franco Pacini K. Rohlfs A. C. De Landtsheer I. D. Zhongolovich C. de Jager A. Greve J. Ruprecht R. J. Tayler G. Kockarts W. I. Axford H. Tabor H. J. Bolle E. Kaldis Gijsbertha C. M. Reijnen C. de Loore J. Kleczek C. A. Murray Åke Wallenquist 《Space Science Reviews》1981,28(1):105-118
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C.K. Shum Hyongki Lee P.A.M. Abusali Alexander Braun Guy de Carufel Georgia Fotopoulos Attila Komjathy Chungyen Kuo 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
Innovative processing of satellite radar altimetry over solid Earth has been successfully applied for observing geodynamic process of glacial isostatic adjustment over the former Laurentide Ice Sheet in the present-day Hudson Bay land region. In this contribution, a simulation is conducted to study the prospects of the applications of space-/airborne and land-based Global Navigation Satellite System (GNSS) reflectometry to synoptically observe global-scale geodynamic processes with a vertical accuracy of ∼2 mm/yr. 相似文献
269.
Effects of X2-class solar flare events on ionospheric GPS-TEC and radio waves over Brazilian sector 总被引:1,自引:0,他引:1
A.J. de Abreu M. Roberto M.A. Alves J.R. Abalde P.A.B. Nogueira K. Venkatesh P.R. Fagundes R. de Jesus M. Gende I.M. Martin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(11):3586-3605
In this investigation, we present and discuss the effects of 6 X2-class solar flare events in the ionospheric F region over Brazilian sector that occurred during 2013 to 2015. For this investigation, we present the vertical total electron content (VTEC) observations from nearly 120 Global Positioning System (GPS) receivers all over the Brazilian sector for each event. Also, ionospheric sounding observations obtained in São José dos Campos (23.2°S, 45.9°W, dip latitude 17.6°S; hereafter referred to as SJC), under the southern crest of the equatorial ionospheric anomaly (EIA), Brazil, are presented. The observations show that the greatest TEC impact occurs with the EUV fluxes increases lasting for more than one hour and when the solar active region is located close to the solar disc center. We present a detailed study of the efficiency of the EUV flux with wavelengths ranging from 0.1 to 190?nm for the F region ionization. The largest increase of ΔTEC occurs below the magnetic equator line, covering mainly the central, northeast, southeast and south regions, which includes the equatorial ionospheric anomaly (EIA) region. The ionograms show partial or total fade out in the echoes traces observed causing blackouts of radio signals of up to 60?min, which can have serious consequences to technological systems of public and private agencies around Brazilian sector. This study can help to better understand the effects of solar flares in the ionospheric F region. 相似文献
270.
L. Perna M. Pezzopane E. Zuccheretti P.R. Fagundes R. de Jesus M.A. Cabrera R.G. Ezquer 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
This paper is focused on unusual nighttime impulsive electron density enhancements that are rarely observed at low latitudes on a wide region of South America, under quiet and medium/high geomagnetic conditions. The phenomenon under investigation is very peculiar because besides being of brief duration, it is characterized by a pronounced compression of the ionosphere. The phenomenon was studied and analyzed using both the F2 layer critical frequency (foF2) and the virtual height of the base of the F region (h′F) values recorded at five ionospheric stations widely distributed in space, namely: Jicamarca (−12.0°, −76.8°, magnetic latitude −2.0°), Peru; Sao Luis (−2.6°, −44.2°, magnetic latitude +6.2°), Cachoeira Paulista (−22.4°, −44.6°, magnetic latitude −13.4°), and São José dos Campos (−23.2°, −45.9°, magnetic latitude −14.1°), Brazil; Tucumán (−26.9°, −65.4°, magnetic latitude −16.8°), Argentina. In a more restricted region over Tucumán, the phenomenon was also investigated by the total electron content (TEC) maps computed by using measurements from 12 GPS receivers. A detailed analysis of isoheight ionosonde plots suggests that traveling ionospheric disturbances (TIDs) caused by gravity wave (GW) propagation could play a significant role in causing the phenomenon both for quiet and for medium/high geomagnetic activity; in the latter case however a recharging of the fountain effect, due to electric fields penetrating from the magnetosphere, joins the TID propagation and plays an as much significant role in causing impulsive electron density enhancements. 相似文献