Buffeting numerical simulation coupled with aerodynamics and structure based on MDDES

Unsteady effect of seriously separated flow is the main factor of modern aircraft buffeting. So accurate simulation of this complex flow becomes the basis associated with the research of aircraft buffeting. This paper constructs an unsteady numerical simulation method for separation flow based on modified delayed detached eddy simulation (MDDES) method by considering both modern computer resources and the credibility of simulating separation flow. The proposed method is also verified through the simulation of the separated flow by a typical fighter at high angle of attack. And then a robust and efficient technology for deforming mesh is established using radial basis function (RBF) and infinite interpolation method. Moreover, the platform for numerical simulation of buffeting is set up in combination with the structural dynamics equations in the modal space, by which the research of vertical tail buffeting caused by edge vortex is carried out on a fighter at large angle of attack. Through spectrum analysis of time-domain response of pressure pulsation on the location of vortex rupture, the results show that the pulsation frequency of vortex structure with different scales covers the inherent modal frequency of vertical tail structure. Compared to the Reynolds-averaged Navier-Stokes equations, the MDDES method can distinguish the more detailed and higher frequency small-scale vortex structure. Unlike flutter, displacement acceleration response of each mode in buffeting is dominated by its own mode. There exists strong coupling between the first bending mode and first torsion mode, and it leads to acceleration and large inertia impact of structure, which is the main factor causing structural fatigue. In sum, the obtained results verify the validity of the numerical means and the corresponding methods in the paper.     

Study of partial discharge characteristics at repetitive square voltages based on UHF method

Due to overvoltage produced by inverter output,inverter-fed motor insulation systems often experience fast electrical aging process,especially when partial discharge(PD) is incepted.Before putting into use,the PD detection should be performed on inverter-fed motors at repetitive square voltages to avoid the PD caused insulation deterioration when the motors are collected to inverters having specific characteristics.However,unlike PD tests at AC/DC voltages proposed in IEC 60270,the PD detection at repetitive square voltages is much more complex because of serious interference generated by impulse generator.To solve the problem,ultra-high frequency(UHF) method seems recommendable for its preferable signal-to-noise ratio(SNR).The chief aim of this study is to investigate PD pulse and statistical characteristics of turn-to-turn insulation for inverter-fed traction motors.A square-shaped Archimedes antenna,specially designed for the PD detection at repetitive square voltages of fast rise times,was used to perform PD tests on turn-to-turn insulation models.Time and frequency analysis results indicate that energy component of generator disturbance and PD pulses are mainly distributed in the 0-0.5 GHz and 0.6-1.5 GHz range,respectively.Based on the results,suitable filter was designed for power disturbance suppression.Additionally,resorting to the sensor unit(i.e.antenna and filter) and the PD test system,the PD statistical features at square voltages of different frequencies were obtained.Experimental results show that higher frequency will give rise,statistically,to PD of lower magnitudes distributing at smaller phases.A reasonable interpretation of this phenomenon was presented.Lastly,according to the PD statistical features,some suggestions for the PD detection system design,generator parameter optimization and the PD pulse extracting were given.The results of this work would be beneficial to the increase of the sensitivity when performing the PD detection on insulation systems for inverter-fed motors at repetitive square voltages and thus,improving the reliability of inverter-fed motors.     

真空环境下的二元冰制备特性研究

采用理论分析与试验相结合的方法,对真空环境下的二元冰生成动态特性进行研究。分析了闪蒸室内压力、水套温度、供水温度、速率、不同水质等各因素对二元冰晶生成的影响。研究结果表明:闪蒸室压力、供水水温、水质以及水滴初始直径、速率都对二元冰真空制备具有较大的影响,其中,闪蒸室压力升高,水滴闪蒸、结冰速率明显下降;供水温度越低,水滴达到同一状态所需的时间越短;水滴初始粒径的增加,水滴闪蒸、结冰的进程明显变慢。闪蒸室温度对水滴的闪蒸、结晶影响不是很大。     

光纤传感技术在岩土工程安全 监测中的应用

详细介绍了光纤光栅传感技术及其特点、光纤BFG光栅传感器技术特性指标及选择,给出了光纤传感技术在国内岩土工程安全监测中成功应用的实例。研究结果为从事岩土工程安全监测设计、现场监测的人员提供参考和借鉴。     

乌江沙沱水电站水轮机选型分析

沙沱水电站水头运行范围50～74.9 m.电站受阻出力多为汛期季节性电能,在综合考虑减少受阻出力及水轮机稳定运行的情况下,对61、62.5、64、65.5、67m五个额定水头方案进行了比较分析,最终确定了经济、合理的水轮机参数.     

佳芦河流域“7·27”暴雨洪水浅析

以佳芦河流域2012年“7·27”暴雨洪水为例,采用场次暴雨洪水资料,分别统计流域面平均雨量、暴雨中心最大2h雨量、大于50 mm以上降雨笼罩面积、次洪洪量、次洪输沙量等指标,分析暴雨洪水输沙关系.结果表明:该次暴雨中心雨量和最大2h雨量最大,面雨量是该地区1971年以来的最大值;与历史洪水相比,相似的降雨量综合因子产生的次洪洪量和次洪沙量具有明显的减少趋势,下垫面削峰作用显著,水土保持成效明显.     

欧盟流域管理模式及其经验借鉴

欧洲流域管理模式注重依法管理、规划管理、综合管理、结果管理和时间管理、协调管理等,形成了完整的水法规框架体系、覆盖主要河流的流域规划体系、完整的水管理目标体系、可操作性强的约束监督机制,并明确了水环境各类目标完成的时限,调动了有关国家流域管理的积极性。结合我国流域管理的现状,借鉴欧盟流域管理模式的经验,我国应构建流域水管理法规体系、实行流域共同管理和流域水环境控制性指标管理,并应强化分级分区域约束机制建设,还应加快控制性工程建设,调整流域管理机构职责和工作方式,提升流域管理服务水平等。     

淹没条件下自激吸气式脉冲射流流场初步研究

运用计算流体动力学软件,对水下自激吸气式脉冲射流流场进行数值计算。结果表明:在模拟工况的运行参数和结构参数下,自激吸气式脉冲射流装置可以产生自吸气;不同水深条件下,装置形成的涡旋气团时间不同、气团形状不同;随着模拟水深的加大,装置内气体浓度以及射流轴心的速度、压力呈现递减趋势。     

浅谈柬埔寨斯登沃代一级水电站大坝复合土工膜心墙的施工

文章主要叙述柬埔寨斯登沃代一级水电站大坝复合土工膜心墙的施工,解决复合土工膜与混凝土刺墙坝的结合难题。电站下闸蓄水后,下游未出现渗水,复合土工膜防渗效果良好,达到了预期防渗的目的。     

长江上游六流域强降水面雨量特征分析

为满足长江流域水文气象预报服务需要,利用2001～2011年气象站点逐日雨量实况资料,以长江上游岷沱江、嘉陵江、乌江、干流宜宾至重庆、干流重庆至万县、干流万县至宜昌流域强降水面雨量为研究对象,研究其频次分布、极值分布特征。结果表明：长江上游六大流域强降水面雨量出现频次具有明显的季节变化和年际变化特征;冬季频次几乎为零,夏季频次最多,春季猛增,秋季陡降;不同流域强降水面雨量等级分布差异较大、极值分布差异明显;重庆至万县、万县至宜昌两个流域月极大值明显大于其他流域,岷沱江流域月极大值明显小于其他流域。