舰载机着舰过程仿真及下落点分析

舰载机着舰是飞机整个飞行过程中的关键环节,受到舰船的运动和海上的大气紊流扰动,是事故多发环节。本文对舰载飞机的着舰环境建立了数学模型,提出了一种基于推力补偿系统与自动驾驶仪系统交联的控制方法,通过仿真比较角稳定和点稳定2种光波束引导着舰方案,得出着舰终端误差。研究成果对于舰载机的着舰引导具有参考价值。     

海洋风场建模及其仿真应用分析

海洋风要素是海洋学和气象学的基本参数,也是影响飞行器和航行器航行性能的重要因素之一。简要概述了海洋风场的基本概念、风速的高度和时距特性、阵风谱和长期分布以及我国海面风场时空变换特征,阐述了海洋风场的准定常风、风切变、急流、大气紊流和随机风的典型数学模型以及风场数值模拟方法,着重分析了海洋风场建模仿真在飞行控制、飞行性能、落点精度等领域的应用研究进展。     

CFCs制冷剂的禁用与对策

1 情况与对策 近年来,随着制冷、空调工业以及化学工业的迅速发展,CFC的大量使用及排放,对大气环境产生了极为严重的影响,造成了大气同温层中臭氧浓度的明显减少,在南极、北极上空出现了大面积的臭氧“空洞”(指低浓度的臭氧区)。到本世纪末,在中欧、亚洲和北美上空的臭氧耗损将在现在的基础上再翻一番,其破坏程度在夏季超过6％,冬季达10％。臭氧每减少1％,有伤害性的紫外线辐射就增加1.5％以上,此将引起皮肤癌、白内障等疾病的发病率增加,严重威     

跨世纪的“民族之鹰”中国“飞豹”传奇——记我国新型歼击轰炸机的研制、试飞和检阅

去年金秋十月的第一天,世界的目光聚集在北京天安门广场的国庆大阅兵,聚焦在飞越天安门上空的飞机方队。美联社评我国庆阅兵展示新武器说,阅兵看飞行,飞行看“飞豹”。 “飞豹”为什么如此引人注目?因为“飞豹”是我国完全依靠自己的力量自行研制的多用途、全天候、超音速歼击轰炸机,荟萃了我国50年航空工业成就,展示了当代航空技术最新发展,是我国自行设计、自行研制、自行生产作战飞机达到一个新水平的标志;是中华民族工业的结晶,     

斯潘塞湾逃生记

一架贝尔-47型直升机平稳飞行在澳大利亚南部的斯潘塞湾1000英尺上空。突然,飞机作了一个180度的旋转。坐在旅客座位上的39岁的史蒂夫·弗兰西斯听到他的朋友、驾驶员唐·厄克特的惊叫声:“我们要掉下去了,老弟!” 史蒂夫警觉地握住扶手。     

发烟剂的大气环境影响评价预测程序(smokeEIA)设计

以高斯模型为基础,用Visual Basic 6.0程序编写了发烟剂的大气环境影响模型(smokeEIA),主要包括数值计算和烟幕的影响评价两方面内容.针对不同发烟剂,模型可适时添加污染物种类和质量标准.通过参数设置,根据所选择的污染物评价因子,可计算在某一风速时不同大气稳定度下,下风向不同距离处污染物的地面浓度,并对计算结果进行大气环境影响评价.     

水下“飞碟”

从UFO到USO 海阔天空,奥秘无穷。第二次世界大战后不久的1947年6月24日下午3时左右,住在美国爱达和州(Idaho)波伊西的一位名叫杰纳斯·亚诺尔德的企业家驾着自用飞机飞到列尼亚山附近时,突然发现北边上空出现大群列队飞行的白色碟状物,他立即向空军作了报告。据当时推算,每个碟状物长度为45到50英尺,时速为1700英里。据说这就是世界上最先出现的有关UFO(不明飞行物体)的报道。自此以后,有关UFO的报道就不断见诸于世界各国的报纸之中。世界上许多国家相继成立了各种官方和民间的研究机     

含初值的遥测速度和位移振动信号时域提取方法研究

针对飞行器在实际飞行试验中,其结构的位移和振动速度很难直接获取,论文提出利用加速度同位移和速度之间的微分关系,通过采集的遥测加速度振动信号在时域内直接进行数值积分获取位移和速度振动信号,考虑位移和速度初始值非零时对积分结果的影响,采用最小二乘拟合多项式方法进行位移和速度初始值的估计,在此基础上对积分结果进行了修正,确保结果的准确性。方法在仿真加速度振动信号上进行了应用,位移和速度获取结果的相对误差可以控制在千分之五以内,高精度的获取结果表明方法的适用性和可靠性,将其应用于飞行器飞行试验实测数据的处理过程中,获取了遥测位移和速度振动信号,结果的置信度较高。     

烟囱热排烟对舰船甲板风下洗影响的大涡模拟

采用低速气流运动控制方程组和湍流大涡模拟方法,研究迎面来风条件下、烟囱热排烟对舰船甲板风下洗气流的影响,得到舰船飞行甲板上空下洗与航向、横向速度随时间的变化。较无热烟气排出,热排烟使飞行甲板上方的下洗速度时均值减小,其脉动幅度增加;飞行甲板上距离机库门相同的位置上,越靠近首尾对称面,热排烟对下洗速度的影响越大;越靠近舰尾区域,热排烟对飞行甲板风下洗速度的影响越小。     

烟囱热排烟对舰船甲板风下洗影响的大涡模拟

采用低速气流运动控制方程组和湍流大涡模拟方法,研究迎面来风条件下、烟囱热排烟对舰船甲板风下洗气流的影响,得到舰船飞行甲板上空下洗与航向、横向速度随时间的变化。较无热烟气排出,热排烟使飞行甲板上方的下洗速度时均值减小,其脉动幅度增加;飞行甲板上距离机库门相同的位置上,越靠近首尾对称面,热排烟对下洗速度的影响越大;越靠近舰尾区域,热排烟对飞行甲板风下洗速度的影响越小。     

An approach to estimation of near-surface turbulence and CO2 transfer velocity from remote sensing data

The air–sea CO₂ exchange is primarily determined by the boundary-layer processes in the near-surface layer of the ocean since it is a water-side limited gas. As a consequence, the interfacial component of the CO₂ transfer velocity can be linked to parameters of turbulence in the near-surface layer of the ocean. The development of remote sensing techniques provides a possibility to quantify the dissipation of the turbulent kinetic energy in the near-surface layer of the ocean and the air–sea CO₂ transfer velocity on a global scale. In this work, the dissipation rate of the turbulent kinetic energy in the near-surface layer of the ocean and its patchiness has been linked to the air–sea CO₂ transfer velocity with a boundary-layer type model. Field observations of upper ocean turbulence, laboratory studies, and the direct CO₂ flux measurements are used to validate the model. The model is then forced with the TOPEX POSEIDON wind speed and significant wave height to demonstrate its applicability for estimating the distribution of the near-surface turbulence dissipation rate and gas transfer velocity for an extended (decadal) time period. A future version of this remote sensing algorithm will incorporate directional wind/wave data being available from QUIKSCAT, a now-cast wave model, and satellite heat fluxes. The inclusion of microwave imagery from the Special Sensor Microwave Imager (SSM/I) and the Synthetic Aperture Radar (SAR) will provide additional information on the fractional whitecap coverage and sea surface turbulence patchiness.     

蒸发波导探测与雷达超视距一致性实验研究

利用出现概率较高的蒸发波导实现舰船雷达、通信等电子系统进行超视距探测和信号传播是目前的研究热点.为了检验蒸发波导的出现与雷达超视距探测的相互关系,采用精度高、反应速度快的大气波导测试仪在海面上空进行蒸发波导的实际测量,同时也利用海岸上的雷达进行探测.实测结果表明,当雷达的工作区域出现蒸发波导时,雷达能够实现超视距探测,且随着蒸发波导的强度不同,雷达探测信号的强度也相应地发生改变,证明了蒸发波导的实际测量与雷达信号实现超视距传播的一致性.     

基于微扰法观察波斯湾环境条件对声散射的影响（英文）

The main goal of this paper is to investigate sound scattering from the sea surface, by Kuo's small perturbation method(SPM), in the Persian Gulf's environmental conditions. Accordingly, the SPM method is reviewed, then it is demonstrated how it can accurately model sound scattering from the sea surface. Since in Kuo's approach, the effects of surface roughness and sub-surface bubble plumes on incident sounds can be studied separately, it is possible to investigate the importance of each mechanism in various scattering regimes. To conduct this study, wind and wave information reported by Arzanah station as well as some numerical atmospheric models for the Persian Gulf are presented and applied to examine sound scattering from the sea surface in the Persian Gulf region. Plots of scattering strength by Kuo's SPM method versus grazing angle for various frequencies, wave heights, and wind speeds are presented. The calculated scattering strength by the SPM method for various frequencies and wind speeds are compared against the results of critical sea tests 7(CST-7). The favorable agreement achieved for sound scattering in the Persian Gulf region is indicative of the fact that the SPM method can quite accurately model and predict sound scattering from the sea surface.     

半潜式钻井平台风载荷CFD预报

在平台设计过程中,海洋平台受到的风载荷是稳性分析与结构设计需要考虑的重要因素。本文采用CFD技术,对某型半潜式钻井平台在作业工况下受到的风载荷进行了预报,分析了湍流模型、风速剖面形式、湍流强度分布等因素对半潜式钻井平台风载荷的影响。结果表明：不同湍流模型对海洋平台风载荷的预报偏差在2%以内,可以忽略湍流模型的影响；风速剖面对风载荷有较大影响,随着风速梯度的增加而增大；湍流强度分布对海洋平台风载荷的影响在6%以内。研究结论可为建立高精度的海洋平台风载荷数值预报方法提供技术支持。     

Joint earthquake and wave action on the monopile wind turbine foundation: An experimental study

Offshore wind turbines in regions of active seismicity are under a potential threat caused by the joint earthquake and ocean wave action. Taking NREL-5MW monopile wind turbine as the prototype, this study is devoted to probe the joint action of strong earthquakes and moderate sea conditions. A series of shake table model tests of scale 30:1 have been carried out by the contemporary world unique facility (Earthquake, Wave and Current Joint Simulation System) to investigate the structural response in dry flume, low and high calm water levels, with and without regular or random waves. Particular interest has been in the nacelle acceleration subjected to strong ground motions as well as to random waves. The experimental results of nacelle peak accelerations and corresponding dynamic amplification factors show that the joint earthquake and wave action is important for the proper evaluation of structural response. Ignoring the effect of wave action in seismic analysis will lead to underestimation of structural response, especially when the monopile foundation is dynamically sensitive. The coupling of earthquake and wave actions is sourced not only from the relative velocity of vibration but also from the initial condition induced by waves. It has been also derived that the peak acceleration excited by a moderate sea condition is comparable to that by a moderate earthquake.     

利用传真地面天气图计算海面风

推导出传真地面天气图上地转风与梯度风的近似计算公式，根据公式制作了地转风与梯度风查算图，并求算了30个站点的海面理论风速值。与实测风速比较，得到了海面摩擦系数和地转风近似法与梯度风近似法计算海面风速的适用条件。     

Parameterization of air–sea gas fluxes at extreme wind speeds

Air–sea flux measurements of O₂ and N₂ obtained during Hurricane Frances in September 2004 [D'Asaro, E. A. and McNeil, C. L., 2006. Measurements of air–sea gas exchange at extreme wind speeds. Journal Marine Systems, this edition.] using air-deployed neutrally buoyant floats reveal the first evidence of a new regime of air–sea gas transfer occurring at wind speeds in excess of 35 m s^− 1. In this regime, plumes of bubbles 1 mm and smaller in size are transported down from near the surface of the ocean to greater depths by vertical turbulent currents with speeds up to 20−30 cm s^− 1. These bubble plumes mostly dissolve before reaching a depth of approximately 20 m as a result of hydrostatic compression. Injection of air into the ocean by this mechanism results in the invasion of gases in proportion to their tropospheric molar gas ratios, and further supersaturation of less soluble gases. A new formulation for air–sea fluxes of weakly soluble gases as a function of wind speed is proposed to extend existing formulations [Woolf, D.K, 1997. Bubbles and their role in gas exchange. In: Liss, P.S., and Duce, R.A., (Eds.), The Sea Surface and Global Change. Cambridge University Press, Cambridge, UK, pp. 173–205.] to span the entire natural range of wind speeds over the open ocean, which includes hurricanes. The new formulation has separate contributions to air–sea gas flux from: 1) non-supersaturating near-surface equilibration processes, which include direct transfer associated with the air–sea interface and ventilation associated with surface wave breaking; 2) partial dissolution of bubbles smaller than 1 mm that mix into the ocean via turbulence; and 3) complete dissolution of bubbles of up to 1 mm in size via subduction of bubble plumes. The model can be simplified by combining “surface equilibration” terms that allow exchange of gases into and out of the ocean, and “gas injection” terms that only allow gas to enter the ocean. The model was tested against the Hurricane Frances data set. Although all the model parameters cannot be determined uniquely, some features are clear. The fluxes due to the surface equilibration terms, estimated both from data and from model inversions, increase rapidly at high wind speed but are still far below those predicted using the cubic parameterization of Wanninkhof and McGillis [Wannikhof, R. and McGillis, W.R., 1999. A cubic relationship between air–sea CO₂ exchange and wind speed. Geophysical Research Letters, 26:1889–1892.] at high wind speed. The fluxes due to gas injection terms increase with wind speed even more rapidly, causing bubble injection to dominate at the highest wind speeds.     

Preoperational ocean forecasting in the southeastern Mediterranean Sea: Implementation and evaluation of the models and selection of the atmospheric forcing

Within the framework of several local and international programs, a quasi-operational ocean-forecasting system for the Southeastern Mediterranean Sea has been established and evaluated through a series of preoperational tests. The Princeton Ocean Model (POM) is used for simulating and predicting the hydrodynamics while the Wave Model (WAM) is used for predicting surface waves. Both models were set up to allow varying resolution and multiple nesting. In addition, POM was set up to be easily relocatable to allow rapid deployment of the model for any region of interest within the Mediterranean Sea. A common requirement for both models is the need for atmospheric forcing. Both models require time varying wind or wind stress. In addition, the hydrodynamic model requires initial conditions as well as time dependent surface heat fluxes, fresh water flux, and lateral boundary conditions at the open boundaries. Several sources of atmospheric forcing have been assessed based on their availability and their impact on the quality of the ocean models' forecasts. The various sources include operational forecast centers, other research centers, as well as running an in-house regional atmospheric model. For surface waves, higher spatial and temporal resolution of the winds plays a central role in improving the forecasts in terms of significant wave height and the timing of various high wave events. For the hydrodynamics, using the predicted wind stress and heat fluxes directly from an atmospheric model can potentially produce short range ocean forecasts that are nearly as good as hindcasts forced with gridded atmospheric analyses. Finally, a high-resolution, nested version of the model has shown to be stable under a variety of forcing conditions and time scales, thus indicating the robustness of the selected nesting strategy. For the southeastern corner of the Mediterranean, at forecast lead times of up to 4 days the high-resolution model shows improved skill over the coarser resolution driving model when compared to satellite derived sea surface temperatures. Most of the error appears to be due to the analysis error inherent in the initial conditions.     

斯里兰卡科伦坡临近海域波浪数值模拟

通过分析斯里兰卡科伦坡港口所处地理位置及气象波浪资料,了解工程海域主要受到季风气候的控制,冬季盛行东北季风,夏季西南季风,热带气旋在经过或影响到斯里兰卡岛时强度较低,风速不是很大,对该区域没有灾害性的影响。文章利用中尺度大气模式MM5模拟历史天气状态,再现1991~2010年20 a的影响工程海域的风场过程。根据得到的风场过程,利用海浪模式SWAN计算科伦坡南港附近海域30 m等深线处各向的波浪要素,并利用卫星观测数据进行结果验证。利用优化后的模型计算了1991~2010年计算方向的波高年极值,P-Ш曲线适线法计算得到不同重现期的外海波要素。     

Response of the Black Sea mean level to atmospheric pressure and wind forcing

The response of the Black Sea mean level to atmospheric pressure (AP) and wind forcing is investigated using 5 years of TOPEX/POSEIDON (T/P hereafter) data. A coherence analysis is first applied to mean sea level and pressure to examine the validity of the inverse barometer (IB) approximation over this area. As expected, it reveals very significant deviations from an IB response attributed to the narrowness of the Bosphorus Strait and its limiting role in water exchanges. A comparison is drawn with the Mediterranean Sea case. A single basin version of the Candela analytical model [Candela, J., 1991. The Gibraltar Strait and its role in the dynamics of the Mediterranean Sea. Dyn. Atmos. Oceans 15, 267–300], which takes linear friction at the strait into account, is then used. The model explains a significant part of the T/P mean sea level variance (about 30%, while the IB correction only explains 5% of its variance) and provides a means to correct the altimeter data for the pressure effect much better than the standard IB effect. The response of the mean sea level to wind forcing is then analysed. Coherence analysis between sea level and along-strait wind stress (WS) reveals a significant coherence at periods ranging from 40 to 100 days, with an almost steady phase of 270°. This result is confirmed with a multiple coherence analysis (mean sea level vs. WS and AP). A plausible mechanism is a piling-up of water at the northern or southern end of the strait due to along-strait wind forcing. The associated along-strait pressure gradient would modify the barotropic flow in the strait and then the mean sea level. Using an extension of the Candela model, we show that this mechanism is consistent with T/P mean sea level observations.