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周期性阵风流对通气航行体超空泡形态及流体动力特性影响 被引量:5
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作者 王威 王聪 +1 位作者 李聪慧 杜严峰 《振动与冲击》 EI CSCD 北大核心 2019年第13期208-214,共7页
使用动态网格技术,数值模拟研究了周期性阵风流对通气航行体的超空泡形态和流体动力特性影响。首先通过数值计算的结果与实验数据对比,验证了动态网格技术数值模拟周期性阵风流的可行性,然后基于该模拟方法分析了周期性阵风流作用下通... 使用动态网格技术,数值模拟研究了周期性阵风流对通气航行体的超空泡形态和流体动力特性影响。首先通过数值计算的结果与实验数据对比,验证了动态网格技术数值模拟周期性阵风流的可行性,然后基于该模拟方法分析了周期性阵风流作用下通气超空泡航行体的空泡形态演化过程及流体动力变化特点。结果表明:在周期性阵风流作用下,通气航行体的超空泡形态呈现周期性变化,航行体沾湿区域的大小和位置也随之发生变化,进而引起了流体动力系数的周期性变化;航行体沾湿区域的阻力占总阻力的比例随着沾湿面积的增加而增大;沾湿区域升力占总升力的比例较大,沾湿区域的空泡闭合线附近存在高压区,使得沾湿区域的面积虽小,但却可以为航行体提供很大的升力。 展开更多
关键词 阵风流 通气超空泡 沾湿区域 体动力
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周期性阵风流作用下通气超空泡的仿真研究 被引量:3
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作者 王威 王聪 +1 位作者 杜严锋 李聪慧 《兵工学报》 EI CAS CSCD 北大核心 2018年第9期1772-1779,共8页
建立周期性阵风流作用下的计算网格模型,得到阵风流作用下的多相流特性,并通过试验数据对比验证了该模型的正确性。基于所建立的模型,通过数值模拟研究了阵风流作用下通气超空泡的变化特性。研究结果表明:流场上游布置的阵风发生器周期... 建立周期性阵风流作用下的计算网格模型,得到阵风流作用下的多相流特性,并通过试验数据对比验证了该模型的正确性。基于所建立的模型,通过数值模拟研究了阵风流作用下通气超空泡的变化特性。研究结果表明:流场上游布置的阵风发生器周期性摆动可以在下游流场中产生阵风流动,阵风发生器频率越高,阵风流波长越小、波幅越大;来流速度越大,阵风流波长越大,波幅越大。流场下游的通气超空泡受到阵风流的作用发生变形,阵风发生器频率越大,超空泡变形越大;来流速度越大,超空泡形态越稳定;阵风流长波对超空泡形态的影响较短波小。空化数受到阵风流的影响而出现周期性变化,超空泡尾部泄气方式也随之出现变化,空化数变大时,超空泡尾部回射流的动量变大,影响了空泡尾部的双涡管泄气方式。 展开更多
关键词 通气超空泡 阵风流 阵风发生器 数值模拟
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相似环流背景下海南两次不同类型强对流天气对比研究 被引量:19
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作者 符式红 王秀明 俞小鼎 《气象学报》 CAS CSCD 北大核心 2018年第5期742-754,共13页
2016年6月5日和6日海南岛处在类似的环流背景下,5日海南出现了大范围8级以上阵风且伴有EF2级龙卷,而次日以短时强降水为主。为了研究两日产生不同类型强对流天气的原因,基于常规地面-高空观测、海南逐10 min的地面加密观测、海口多普勒... 2016年6月5日和6日海南岛处在类似的环流背景下,5日海南出现了大范围8级以上阵风且伴有EF2级龙卷,而次日以短时强降水为主。为了研究两日产生不同类型强对流天气的原因,基于常规地面-高空观测、海南逐10 min的地面加密观测、海口多普勒雷达观测、NCEP-GFS 0.5°×0.5°分析资料进行对比分析,结果表明:(1)5日整层大气相对较干(可降水量为49 mm)且中层干层尤为清晰(700—500 hPa平均相对湿度41%),925—700 hPa温度垂直递减率为7.25℃/km,有利于产生强下沉气流及冷池形成,从而产生雷暴大风天气,而6日气层高湿,可降水量为60 mm,环境风弱,风暴移速慢,有利于产生强降水;(2)两日均属于弱的环境背景气流下的对流,相对而言,5日0—3 km风垂直切变均较6日大,有利于形成飑线;(3)结构分析表明5日对流风暴伴有较强阵风出流,较强的风垂直切变加之多个单体阵风出流合并抬升下,产生了持续1.5 h的飑线,并出现了弓形回波,而6日为低质心一般单体且阵风出流相对弱,尽管多个单体合并成了准线性的风暴,其持续时间亦与一般单体生命史相当;(4)5日对流抑制能量相对较大,需较强的地面辐合抬升和午后强烈升温触发雷暴,雷暴触发后强烈发展;6日对流抑制能量近乎为0,弱的海风锋辐合及热力作用均触发对流;(5)此次龙卷过程的风垂直切变与典型超级单体龙卷差异显著,产生龙卷的低层中气旋出现时间与龙卷发生时间仅差3 min,故提前预警龙卷的可能性极小。 展开更多
关键词 雷暴大风 短时强降水 风暴阵风 风暴结构
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Role of the interaction between a gust front and a mesoscale air mass boundary in convection initiation:a case study 被引量:2
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作者 CUI Xinyan QIN Rui +1 位作者 CHEN Mingxuan HAN Lei 《Atmospheric and Oceanic Science Letters》 CSCD 2019年第5期337-342,共6页
The local convection initiation(CI)mechanisms of a convective case that occurred on5 August 2017 in Cangzhou,northern China,were studied using Doppler radar and automatic weather station observational analysis,along w... The local convection initiation(CI)mechanisms of a convective case that occurred on5 August 2017 in Cangzhou,northern China,were studied using Doppler radar and automatic weather station observational analysis,along with Variational Doppler Radar Analysis System assimilation analysis.During the convective process,a gust front appeared ahead of two existing convective systems,respectively.In the warm and moist environment ahead of the gust fronts in the south,there was a mesoscale air mass boundary.With the process of a gust front moving southward,approaching the mesoscale air mass boundary,the convergence intensified in the area between the gust front and the mesoscale air mass boundary.Finally,the strong convergent updraft exceeded the level of free convection and triggered the new convection. 展开更多
关键词 Convection initiation gust front mesoscale air mass boundary 4D variational data assimilation
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The Application of Risk Matrix in Risk Appraisal of Brand Cultivation and Formation of Logistics industry
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作者 Haocheng WANG 《International Journal of Technology Management》 2013年第9期58-60,共3页
This paper first analyzes the main potential risks in brand cultivation and formation of logistics enterprise. After that, based on field interview and questionnaire survey conducted in logistics enterprises of Guangx... This paper first analyzes the main potential risks in brand cultivation and formation of logistics enterprise. After that, based on field interview and questionnaire survey conducted in logistics enterprises of Guangxi and Hunan provinces, the author applies the risk matrix and Borda order method to appraise the risks in brand cultivation and formation of logistics industry and how to prevent these risks. 展开更多
关键词 logistics industry brand cultivation and formation risk matrix risk prevention
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Copula-Based Monte Carlo Scenarios Generation Method for STOPF Problem 被引量:1
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作者 Li Jinghua Lan Fei 《Electricity》 2014年第2期41-50,共10页
This paper introduces a Monte Carlo scenario generation method based on copula theory for the stochastic optimal power flow (STOPF) problem with wind power. By using copula theory, the scenarios are simulated from m... This paper introduces a Monte Carlo scenario generation method based on copula theory for the stochastic optimal power flow (STOPF) problem with wind power. By using copula theory, the scenarios are simulated from multivariable joint distribution but only from their dependency matrix. Hence, the scenarios generated by proposed method can contain flail statistical information of multivariate. Here, the details of simu- lating scenarios for multi-wind-farm are explained with four steps: determine margin of one wind farm, fit the copulas, choose optimal copulas and simulate scenarios by Mote Carlo. Moreover, the producing process of scenarios is demonstrated by two adjacent actual wind farms in China. With the scenarios, the STOPF is con- verted into the same amount deterministic sub OPF models which can be solved by available technology per- fectly. Results using copula theory are compared against results from history samples based on two designs: IEEE 30-bus and IEEE 118-bus systems. The comparison results prove the accuracy of the proposed methodology. 展开更多
关键词 multi-wind-farm correlation relationship copula function scenario generation stochastic programming
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A reduced-order-model-based multiple-in multiple-out gust alleviation control law design method in transonic flow 被引量:2
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作者 CHEN Gang WANG Xian LI YueMing 《Science China(Technological Sciences)》 SCIE EI CAS 2014年第2期368-378,共11页
Gust alleviation is very important to a large flexible aircraft.A nonlinear low-order aerodynamic state space model is required to model the nonlinear aeroelastic responses due to gust.Based on the proper orthogonal d... Gust alleviation is very important to a large flexible aircraft.A nonlinear low-order aerodynamic state space model is required to model the nonlinear aeroelastic responses due to gust.Based on the proper orthogonal decomposition method,a reduced order modeling of gust loads was proposed.And then the open-loop and closed-loop reduced order state space model for the transonic aeroelastic system was developed.The static output feed back control scheme was used to design a simple multiple-in multiple-out(MIMO)gust alleviation control law.The control law was demonstrated with the Goland+wing model with four control surfaces.The simulation results of different discrete gusts show the capability and good performance of the designed MIMO controller in transonic gust alleviation. 展开更多
关键词 transonic gust alleviation reduced order model proper orthogonal decomposition static output feed back
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