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Design and Experiment of Streamlined Piezoelectric Pump with Low Vortex and Large Flow Rate 被引量:1
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作者 BIAN Kan HUANG Zhi +4 位作者 BAO Qibo ZHANG Jianhui LAI Liyi CHEN Xiaosheng CHEN Zhenlin 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI CSCD 2020年第1期155-163,共9页
Valveless piezoelectric pump is widely used in the medical,however,there is a general and difficult problem to be solved:Low vortex and large flow rate are not compatible,resulting in the blood prone to thrombosis dur... Valveless piezoelectric pump is widely used in the medical,however,there is a general and difficult problem to be solved:Low vortex and large flow rate are not compatible,resulting in the blood prone to thrombosis during blood delivery.In this paper,a new valveless piezoelectric(PZT)pump with streamlined flow tubes(streamlined pump)is proposed.The design method and the working principle of the pump are analyzed.The velocity streamlines are simulated,and the results demonstrate that there are no obvious vortexes in the flow tube of the streamlined pump.Five prototype pumps(two cone pumps and three streamlined pumps)are designed and fabricated to perform flow rate and flow resistance experiments.The experimental results illustrate that the maximum flow rate of the streamlined pump is 142 mL/min,which is 179%higher than that of the cone piezoelectric pump,demonstrating that the streamlined pump has a large flow rate performance.This research provides an inspiration for future research on simple structure,low vortex and large flow rate volume-type pumps,and also provides a useful solution for thrombosis preventing. 展开更多
关键词 valveless piezoelectric pump streamlined low vortex high flow rate THROMBOSIS
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NUMERICAL SIMULATION OF EXTREMELY HEAVY RAIN AND MESO-β SCALE LOW VORTEX IN INVERTED TYPHOON TROUGH 被引量:4
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作者 姜勇强 王昌雨 +1 位作者 张维桓 陈中一 《Acta meteorologica Sinica》 SCIE 2004年第2期195-210,共16页
Large-scale and mesoscale analyses are made for extremely heavy rain (EHR) and meso-β scale low vortex (MSLV) in Jiading District of Shanghai Municipality during 6-7 July 2001.It is shown that the EHR forms in the si... Large-scale and mesoscale analyses are made for extremely heavy rain (EHR) and meso-β scale low vortex (MSLV) in Jiading District of Shanghai Municipality during 6-7 July 2001.It is shown that the EHR forms in the situation of northern westerly trough linking together with southern inverted typhoon trough at northwest side of the West Pacific Ocean subtropical high. Numerical simulation is made using a 21-layer improved REM (regional η coordinate model) for this course.The results show that the precipitation forms earlier than MSLV.and the strong convergence in wind velocity mate (WVM) triggers the strong precipitation.The formative reasons of WVM.especially the weak wind velocity center are discussed,and the formative mechanisms of the MSLV and EHR are discussed using high spatial and temporal resolution model- output physical fields.The results show that the heavy rain releases latent heat and warms the air column,and enhances the low level positive vorticity that existed before.Then it causes the formation of MSLV.There is a positive feedback mechanism between low vortex and precipitation,so CISK must be an important mechanism. 展开更多
关键词 extremely heavy rain (EHR) meso-B scale low vortex (MSLV). wind velocity mate (WVM). inverted typhoon trough numerical simulation
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Doppler Radar Data Analysis of A Low-shear Vortex System in Northern Guizhou 被引量:3
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作者 李明元 张沪生 《Meteorological and Environmental Research》 CAS 2010年第1期34-38,共5页
With Zunyi CINRAD/CD Doppler radar data and other data,a hail wind and heavy rainfall in short time occurred on July 10,2008 in northern Guizhou Province was analyzed in this study.The results showed that the system w... With Zunyi CINRAD/CD Doppler radar data and other data,a hail wind and heavy rainfall in short time occurred on July 10,2008 in northern Guizhou Province was analyzed in this study.The results showed that the system was affected by the southward of cold air pressure in a low-shear vortex zone.Echo monomer initially developed and arranged along the shear line,and there was hail weather in echo location with intense development.Before the hail shooting,the strongest echo value was 60-65 dBz.When the hail shooting,the low-elevation echo intensity sharply increased to 55-60 dBz with echo height of 11-15 km and VIL values>35 kg/m2,and its echo distribution showed band characteristics of vortex.When the vortex center moved to the original echo,echo intensity increased,resulting in a profound and lasting convergence of cyclones,and hail or strong wind occurred on the ground.Hail and strong short-term precipitation in towns of northern Renhuai might be related to the left inverted U-terrain.Echoes from Yongxing and Yuquan in Meitan,Xuekong and Xitou in Renhuai were the supercell echoes,and other regional hail shooting echoes were strong multi-monomer echoes. 展开更多
关键词 low-shear vortex Doppler radar Echo characteristics China
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Research on the dry intrusion accompanying the low vortex precipitation 被引量:11
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作者 YAO XiuPing1,2,3, WU GuoXiong1, ZHAO BingKe4, YU YuBin3 & YANG GuiMing2,5 1 LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China 2 Institute of Heavy Rain, China Meteorological Administration, Wuhan 430074, China +2 位作者 3 China Meteorological Administration Training Center, Beijing 100081, China 4 Shanghai Typhoon Institute of China Meteorological Administration, Shanghai 200030, China 5 National Meteorological Center of the China Meteorological Administration, Beijing 100081, China 《Science China Earth Sciences》 SCIE EI CAS 2007年第9期1396-1408,共13页
By employing the 6.7μm satellite vapor cloud images and NCEP/NCAR 1°×1° reanalysis datasets, the characteristics and mechanism of the dry intrusion, as well as its impacts on the low vortex precipita- ... By employing the 6.7μm satellite vapor cloud images and NCEP/NCAR 1°×1° reanalysis datasets, the characteristics and mechanism of the dry intrusion, as well as its impacts on the low vortex precipita- tion at the Meiyu front are explored in this paper. It is found that the formation,development and main- tenance of the low vortex precipitation at the Meiyu front are closely related to the evolution of the dry intrusion. The dry intrusion is characterized by high potential vorticity (PV), low humidity and cold air. The dry intrusion exhibits as an obvious dark zone on vapor cloud images, an area in which atmos- pheric relative humidity is lower than 60%. However, the features of the dry intrusion on the vapor im- ages are clearer than that of the humidity field, for the former is the digital vapor cloud images with high temporal and spatial resolution, and it can be used to explore the finer characteristics of the develop- ment, evolution and supplement of the intrusion during the development of the low vortex. The dry intrusion impacts accompanying the low vortex precipitation at the Meiyu front come from all levels of the troposphere, with the strongest intrusion located at the upper troposphere. The dry and cold air intrudes the vicinity of the low vortex from the upper isentropic surface to the lower one, slanting eastward from lower to higher level. The low vortex precipitation region is usually situated in front of the dry intrusion where the relative humidity gradient is higher. The research also reveals that the mechanism of the dry intrusion is that the high potential vorticity descends from the upper troposphere to the lower level, therefore, the dry intrusion can be used as an important index of the high PV forcing. To the west of the low vortex precipitation, the upper level northerlies descend across the isentropic surface, then the dry cold advection can trigger the instable development in the mid-low troposphere. The dry intrusion enhances the low vortex precipitation. Meanwhile, because of the good agreement between the high PV at the upper level and the dry intrusion illustrated by the vapor cloud images, the dry intrusion in the vapor cloud images is the direct and clear description of the high PV forcing which provides a new insight in understanding the evolution and development of the practical weather sys- tems. Besides, both the skills of isentropic analysis and potential temperature coordinates system analysis are important to revealing the three-dimension structure of the dry intrusion. 展开更多
关键词 MEIYU front low vortex precipitation dry intrusion mechanisim vapor image potential vorticity relative humidity
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Study of vortex in flow fields induced by surface dielectric barrier discharge actuator at low pressure based on Q criterion 被引量:2
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作者 张政 车学科 +5 位作者 聂万胜 李金龙 郑体凯 李亮 陈庆亚 郑直 《Plasma Science and Technology》 SCIE EI CAS CSCD 2018年第1期41-46,共6页
Flow fields induced by a surface dielectric barrier discharge actuator at low pressure of 7 kPa are measured by particle image velocimetry. The distribution of local vortices in the flow field is revealed by the Q cri... Flow fields induced by a surface dielectric barrier discharge actuator at low pressure of 7 kPa are measured by particle image velocimetry. The distribution of local vortices in the flow field is revealed by the Q criterion. The reason for the generation of vortices is analyzed and the influence of pulse frequency and duty cycle on vortices is studied. The results show that the Q criterion can reveal the small-scale vortices, which cannot be indicated by the streamline. The direction transition zone where the induced jet moves from the vertical to the tangential and the shear layer between the jet and stationary air are prone to the generation of strong vortices. The influence of pulse frequency on vortices is not obvious, but the variation of duty cycle can significantly affect the strength and distribution of vortices. 展开更多
关键词 low pressure SDBD induced field Q criterion vortex
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Contrast Analysis of Two Low Vortices Weather Processes 被引量:1
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作者 廖国进 黄阁 孟鹏 《Meteorological and Environmental Research》 CAS 2010年第4期68-71,91,共5页
Two cold vortex weather processes in Liaoning Province in June of 2006 were analyzed.In the process of low vortex of June 3,strong convection weather,such lightning storm and hailstone,came forth in most areas of Liao... Two cold vortex weather processes in Liaoning Province in June of 2006 were analyzed.In the process of low vortex of June 3,strong convection weather,such lightning storm and hailstone,came forth in most areas of Liaoning Province.White and bright cloud was shown in satellite nephogram.Bow echo and cyclonic circumfluence were shown in weather radar production.In the process of low vortex of June 14,strong precipitation weather came forth in most area of Liaoning Province.Based on the velocity field production of weather radar,the relative place of front and radar station can be judged.The weather situation and forecast were the main basis of short-term prediction.And satellite nephogram,weather radar,automatic weather station play important roles in the monitoring and short-term prediction of disaster weathers. 展开更多
关键词 low vortex Weather situation Satellite nephogram Weather radar Intensity field Velocity field Automatic station data China
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不同天气尺度强迫下陕西暴雨的成因对比
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作者 赵强 彭力 +3 位作者 赵世发 陈小婷 屈丽玮 欧阳雨 《高原山地气象研究》 2024年第2期58-67,共10页
选取常规高空观测资料、地面加密观测资料和ERA5(0.25°×0.25°)再分析资料,对2020年8月4—7日陕西持续性暴雨过程进行诊断分析,并探讨了暴雨发生发展的物理机制。结果表明:暴雨过程分为两个阶段,分别是5日陕北区域暴雨和... 选取常规高空观测资料、地面加密观测资料和ERA5(0.25°×0.25°)再分析资料,对2020年8月4—7日陕西持续性暴雨过程进行诊断分析,并探讨了暴雨发生发展的物理机制。结果表明:暴雨过程分为两个阶段,分别是5日陕北区域暴雨和7日陕西中南部暴雨,二者的环流背景差异显著;5日暴雨的主要影响天气系统是高空槽、低空急流和低涡,中低层急流强且维持时间长,系统涡度大、辐合强,天气尺度强迫强;7日暴雨的主要影响天气系统是短波槽和低层切变,中低层大气风速小,系统涡度小,辐合相对弱,天气尺度强迫较弱。4—5日中低层大气水汽输送强,水汽输送较气候态偏大3~4σ;700 hPa西南急流和850 hPa东南急流给陕北带来充沛的水汽,中低层大气存在明显低涡,大气湿斜压性强,同时低涡南侧有明显锋生,次级环流增强上升运动,水汽在低涡中心及右侧强烈辐合抬升,强降水得以维持;800~700 hPa存在条件对称不稳定,进一步增强上升运动,异常充沛的水汽供应和偏强的低涡造成持续的上升运动是本阶段产生极端大暴雨的主要原因。6—7日陕西中南部水汽输送较弱,水汽辐合强度较小,但本地可降水量大;暴雨区为暖湿大气控制,对流不稳定较强,对流有效位能大,切变线辐合抬升触发对流,降水对流性更强;本阶段强降水较为分散,但雨强大且持续时间短,与地形关系密切。 展开更多
关键词 暴雨 低涡 锋生 大气不稳定度 条件对称不稳定
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一次江淮气旋引起的区域大暴雨可预报性分析及模式检验
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作者 梁钰 张亚春 +2 位作者 董俊玲 席乐 李可 《河南科学》 2024年第11期1644-1652,共9页
利用常规观测资料和逐6 h的ERA5空间分辨率为0.25°×0.25°的再分析资料及数值产品,采用天气学分析和物理量诊断等方法,对河南2020年6月一次江淮气旋区域大暴雨的可预报性进行分析.结果表明:(1)强降水主要出现在850 hPa低... 利用常规观测资料和逐6 h的ERA5空间分辨率为0.25°×0.25°的再分析资料及数值产品,采用天气学分析和物理量诊断等方法,对河南2020年6月一次江淮气旋区域大暴雨的可预报性进行分析.结果表明:(1)强降水主要出现在850 hPa低涡前部西南急流出口区顶部和切变线两侧50~100 km的重叠区域内、地面气旋辐合线附近及左侧冷暖空气交汇处,以冷区降水为主.(2)水汽和动力条件均具有极端性,PWAT、Q850、Qu850、垂直上升运动速度值均超过了河南各类型100 mm以上强降水统计阈值.(3)850 hPa低涡的移动方向和地面3 h负变压中心移动方向对地面气旋的移动有引导作用,负变压中心较气旋中心出现时间早12 h左右.(4)数值模式EC在24~240 h内、CMA-GFS在24~168 h内晴雨准确率和小雨量级TS评分>0.8,暴雨及以下量级的降水TS评分24~72 h内CMA-GFS优于EC,96 h后CMA-GFS低于EC.(5)EC和CMA-GFS强降水落区较实况偏北0.7~0.8个纬度. 展开更多
关键词 江淮气旋 低涡 区域性大暴雨 切变线 模式检验
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Design and Numerical Simulation of Low-Fiber Hollow Spindle in Air-Jet Vortex Spinning 被引量:1
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作者 张肖斌 薛文良 程隆棣 《Journal of Donghua University(English Edition)》 EI CAS 2015年第1期119-124,共6页
Based on the mechanical system of free-end fibers and the analysis of pulling free-end fibers out of the spun yarn during spinning,a low-fiber hollow spindle is designed and the air distribution of fluent field is sim... Based on the mechanical system of free-end fibers and the analysis of pulling free-end fibers out of the spun yarn during spinning,a low-fiber hollow spindle is designed and the air distribution of fluent field is simulated numerically. The negative pressure effect is much bigger at the top of low-fiber hollow spindle than that in Murata No.861,which is more conducive for single fiber to get into the channel of hollow spindle. The tangential velocity in 0-3 mm at the top of hollow spindle increases and the fluctuation of radial velocity is much stronger,which enhance the wrapping effect. In the addition,the distribution of axial velocity remains the same. 展开更多
关键词 air-jet vortex spinning numerical simulation free-end fiber mechanical system low-fiber hollow spindle
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机翼翼尖涡与平尾翼尖涡的相互作用研究
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作者 张泽宇 李栋 +2 位作者 周金鑫 梁勇 耿子海 《实验流体力学》 CAS CSCD 北大核心 2024年第5期29-36,共8页
飞机尾涡的发展与同跑道降落后机的飞行安全及机场起降效率密切相关。尾涡近场特性主要决定了着陆阶段飞机的尾涡强度。以A320飞机简化缩比模型为研究对象,在1 m×1 m低速水洞中开展了尾涡近场形态流动显示实验。研究结果表明:平尾... 飞机尾涡的发展与同跑道降落后机的飞行安全及机场起降效率密切相关。尾涡近场特性主要决定了着陆阶段飞机的尾涡强度。以A320飞机简化缩比模型为研究对象,在1 m×1 m低速水洞中开展了尾涡近场形态流动显示实验。研究结果表明:平尾涡在拖出过程中围绕翼尖涡旋转,不同流向站位的旋转角速度存在差异。对比模拟结果发现:平尾涡绕翼尖涡的旋转角速度与实验结果基本吻合,说明不同雷诺数下涡对发展在相对位置旋转角速度特性方面具有一定相似性。 展开更多
关键词 翼尖涡 旋转角速度 平尾涡 数值模拟 低速水洞
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Analysis of Heavy Precipitation Process in Eastern China from July 26 to 29, 2022
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作者 Yuke Zhang 《Journal of Geoscience and Environment Protection》 2024年第7期122-129,共8页
Based on the data of the National Climate Center of China and the NCEP of the United States, a heavy precipitation process in eastern China during July 26-29, 2022 was analyzed. The results show that: The precipitatio... Based on the data of the National Climate Center of China and the NCEP of the United States, a heavy precipitation process in eastern China during July 26-29, 2022 was analyzed. The results show that: The precipitation process was formed under the influence of the low level southwest jet stream at the edge of the subtropical high. The eastward development of the low vortex and trough and the continuous strengthening of the upper level jet stream, combined with the influence of topographic convergence, provided extremely favorable conditions for the occurrence of the rainstorm. 展开更多
关键词 Southwest Jet low vortex low Trough Topographic Convergence RAINSTORM
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昆仑山北坡“6·14”极端暴雨过程的中尺度对流系统特征分析
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作者 李晓萌 杨莲梅 +1 位作者 李建刚 刘晶 《干旱区地理》 CSCD 北大核心 2024年第10期1700-1712,共13页
在全球变暖的背景下,昆仑山北坡极端暴雨频发且影响巨大,由于对其的观测和研究相对匮乏,使得该区域暴雨监测和预报难度大。理解其发生机理和关键影响系统是提高其监测预报的有效途径,对该区域防灾减灾意义重大。利用高时空分辨率的气象... 在全球变暖的背景下,昆仑山北坡极端暴雨频发且影响巨大,由于对其的观测和研究相对匮乏,使得该区域暴雨监测和预报难度大。理解其发生机理和关键影响系统是提高其监测预报的有效途径,对该区域防灾减灾意义重大。利用高时空分辨率的气象观测资料、GPS/Met大气可降水量(PWV)资料、风云卫星资料(FY-2H)和ERA5再分析资料,对2021年6月14—17日昆仑山北坡一次极端暴雨过程进行大尺度环流背景场和中尺度对流系统特征分析。结果表明:(1)此次暴雨过程,暴雨站数多、累积降水量大、局地性强并且极端性强,在和田地区出现3个极端暴雨中心,分别发生了短时强降水和连续性降水。其中短时强降水过程持续时间短,最大小时雨强达29.4 mm;连续性降水持续时间达3 d,小时雨强小于5 mm。本次极端暴雨发生的有利环流背景是双体型南亚高压在对流层高层维持,中亚低涡形成发展。在高低空急流共同作用下,高层强辐散、低层辐合促进大气垂直运动发展,500 hPa偏南气流、700 hPa切变线以及850 hPa偏东气流相互配合为暴雨提供有利动力配置。(2)对流层中层以西南路径和西南+南方路径水汽输送为主,低层主要以低空偏东急流携带水汽输送为主,中低层水汽输送路径形成耦合,促进本次极端暴雨的发展加强。极端暴雨发生前持续的水汽输送和强的水汽通量辐合中心,使得暴雨区大气可降水量(PWV)在降水前出现显著增湿聚集过程,PWV达30 mm。(3)列车效应型+合并加强型中尺度对流云团不断在暴雨站点上空生成发展并移过,是触发短时强降水的直接影响系统,站点位于对流云团黑体亮温(TBB)梯度最大处。中-β和中-α尺度对流云团发展维持以及涡旋状中尺度对流云带的持续覆盖,是导致暴雨站点发生连续性降水的关键系统。 展开更多
关键词 极端暴雨 中亚低涡 水汽输送 中尺度对流系统 昆仑山北坡
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基于多种分析方法的低压涡轮边界层流动特性研究
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作者 孙爽 黄禛 +3 位作者 康晋辉 孙小鹏 王茂茂 卢乐晗 《中国民航大学学报》 CAS 2024年第5期36-44,共9页
为探究航空发动机低压涡轮吸力面边界层受尾迹影响下的非定常流动特性,本文采用商用软件CFX 15.0进行数值模拟,并使用具有上游尾迹模拟功能的叶栅实验台进行了实验验证。首先,在保持轴向转速不变的情况下,调整上游尾迹杆转速实现了3种... 为探究航空发动机低压涡轮吸力面边界层受尾迹影响下的非定常流动特性,本文采用商用软件CFX 15.0进行数值模拟,并使用具有上游尾迹模拟功能的叶栅实验台进行了实验验证。首先,在保持轴向转速不变的情况下,调整上游尾迹杆转速实现了3种不同的上游尾迹折合频率。其次,利用数值模拟得到了3种工况下低压涡轮吸力面边界层流场数据并进行对比分析,分析中特别使用了本征正交分解(POD,proper orthogonal deco-mposition)、动态模态分解(DMD,dynamic mode decomposition)和傅里叶模态分解(FMD,Fourier mode decomposition)3种新式流场分析方法。结果表明,在3种折合频率下,尾迹中心通过分离区域时,其距离叶面的高度差别较大,尾迹作用下的吸力面边界层中尾迹的影响程度与识别到的主要特征也存在较大差别。 展开更多
关键词 低压涡轮 边界层 尾迹 分离 卷升涡
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2001—2015年4—9月九龙涡时空分布与动力热力特征
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作者 慕丹 李跃清 +3 位作者 吴遥 赵衍斌 禹婷 高雅 《高原山地气象研究》 2024年第3期1-8,共8页
本文利用ERA5再分析资料,通过人工识别统计了2001—2015年4—9月四类不同生命史九龙低涡的时空分布,并对其生成前6 h动力热力特征进行了合成分析。结果表明:(1)2001—2015年4—9月四类九龙涡共有221个;维持时间小于4个时次的九龙涡(T_(1... 本文利用ERA5再分析资料,通过人工识别统计了2001—2015年4—9月四类不同生命史九龙低涡的时空分布,并对其生成前6 h动力热力特征进行了合成分析。结果表明:(1)2001—2015年4—9月四类九龙涡共有221个;维持时间小于4个时次的九龙涡(T_(1~2)JLV、T_(3~4)JLV)生成源地集中在27°~28.5°N、100°~101.5°E;维持时间为5~6个时次的九龙涡(T_(5~6)JLV)生成源地集中在29°~30.3°N、102°~103.5°E;维持时间不低于7个时次的九龙涡(T_(≥7)JLV)生成源地集中于28°~29.5°N、101.5°~103.5°E。(2)生成前6 h,九龙涡生命史越长,其生成源地高频中心周围的低层气旋性环流场更明显,500 hPa副热带高压位置更偏西偏北,200 hPa南亚高压范围更广。(3)生成前6 h,四类九龙涡高频中心周围中低层均为正涡度,低层呈东北-西南向分布,九龙涡生命史越长,其正涡度带越狭长且范围越广。(4)生成前6 h,四类九龙涡高频中心附近低层辐合而中高层辐散,九龙涡生命史越长,其水汽通量散度越强,且越往高层辐散强度越大,但最大辐散强度仍小于低层辐合强度。(5)生成前6 h,九龙涡生命史越长,其生成源地高频中心附近层结越不稳定,更有利于低涡的进一步发展和维持。 展开更多
关键词 九龙低涡 时空分布 环流特征 水汽输送 假相当位温
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The Impact of Deformation on Vortex Development in a Baroclinic Moist Atmosphere 被引量:6
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作者 Na LI Lingkun RAN Shouting GAO 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2016年第2期233-246,共14页
A mathematical relation between deformation and vertical vorticity tendency is built by introducing the frontogenesis function and the complete vertical vorticity equation, which is derived by virtue of moist potentia... A mathematical relation between deformation and vertical vorticity tendency is built by introducing the frontogenesis function and the complete vertical vorticity equation, which is derived by virtue of moist potential vorticity. From the mathematical relation, it is shown that properly configured atmospheric conditions can make deformation exert a positive contribution to vortex development at rates comparable to other favorable factors. The effect of deformation on vortex development is not only related to the deformation itself, but also depends on the current thermodynamic and dynamic structures of the atmosphere, such as the convective stability, moist baroclinicity and vertical wind shear (or horizontal vorticity). A diagnostic study of a heavy-rainfall case that occurred during 20-22 July 2012 shows that deformation has the most remarkable effect on the increase in vertical vorticity during the rapid development stage of the low vortex during its whole life cycle. This feature is mainly due to the existence of an approximate neutral layer (about 700 hPa) in the atmosphere where the convective stability tends to be zero. The neutral layer makes the effect of deformation on the vertical vorticity increase significantly during the vortex development stage, and thus drives the vertical vorticity to increase. 展开更多
关键词 DEFORMATION low vortex VORTICITY frontogenesis function
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一次华北极端降雪天气过程的中尺度涡旋特征
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作者 翟亮 邢楠 +3 位作者 郝翠 王颖 刘文军 仲跻芹 《气象》 CSCD 北大核心 2024年第9期1120-1128,共9页
利用ERA5逐小时再分析数据和实况观测资料,对2020年2月13—14日华北极端雨雪天气过程中的中尺度涡旋进行特征分析,并采用相对涡度的环流积分变化方程对中尺度涡旋的发展机制进行诊断。结果表明:中尺度涡旋活动区域(简称涡旋区)的平均涡... 利用ERA5逐小时再分析数据和实况观测资料,对2020年2月13—14日华北极端雨雪天气过程中的中尺度涡旋进行特征分析,并采用相对涡度的环流积分变化方程对中尺度涡旋的发展机制进行诊断。结果表明:中尺度涡旋活动区域(简称涡旋区)的平均涡度垂直廓线呈“S”型分布,正负涡度极值分别位于800 hPa及400 hPa。涡旋区内800 hPa正涡度强度与上升运动大值区一致。900~700 hPa平均涡度强度与平原地区降水强度同相位变化,涡旋强度的峰值较降水强度峰值早约2 h,二者相关系数为0.76,说明低层涡度强度对降雪预报具有指示性。从涡旋发展的动力机制来看,涡旋区800 hPa以下正涡度主要源自水平风辐合;800~700 hPa上升运动与风随高度顺转对涡度的贡献更大。对比无中尺度涡旋的降雪过程(2019年2月14日),涡旋区内垂直方向涡度无“S”型结构,且中低层涡度较弱,北京降雪量明显偏小。涡旋区是否存在中尺度涡旋发展,对北京冬季降雪量级和极端性的预报有指示意义。 展开更多
关键词 降雪 低涡 中尺度涡旋 涡度收支
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陕北两次不同强度的区域性暴雨过程特征对比
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作者 刘胜男 屈丽玮 +1 位作者 张蔚然 赵强 《高原山地气象研究》 2024年第3期48-57,共10页
利用ERA-5逐小时再分析资料、雷达资料、地面加密站和常规探空资料,对2019年7月21日和2020年8月4日陕北地区两次不同强度的暴雨过程进行对比分析。结果表明:(1)强降水的持续性是造成“0804”过程累计降水量大于“0721”过程的直接原因。... 利用ERA-5逐小时再分析资料、雷达资料、地面加密站和常规探空资料,对2019年7月21日和2020年8月4日陕北地区两次不同强度的暴雨过程进行对比分析。结果表明:(1)强降水的持续性是造成“0804”过程累计降水量大于“0721”过程的直接原因。(2)“0804”过程中,陕北上空层-积混合云回波在夜间的走向和移动方向一致,“列车效应”使低质心暖云降水长时间维持。(3)两次过程降水强度的区别与高低空急流、低涡路径和水汽有密切联系。与“0721”过程相比,“0804”过程中200 hPa高空急流更为稳定,700 hPa西南急流强度更大,强雨带更靠近低涡中心,动力抬升和水汽辐合均偏强。(4)两次过程对流触发机制存在差异,“0804”过程前期地面较强的偏东风更有利于地形抬升。 展开更多
关键词 暴雨 陕北 高低空急流 低涡 水汽输送
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超低负荷工况下汽轮机末级运行特性及其优化机制探索
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作者 彭世亮 王卫良 +3 位作者 吕俊复 柯希玮 刘志东 马庆中 《热力发电》 CAS CSCD 北大核心 2024年第6期65-78,共14页
构建以新能源为主体的新型电力系统,对燃煤发电机组深度调峰和超低负荷运行提出了越来越严苛的要求,进而对汽轮机组低负荷安全运行提出了越来越严峻的挑战。采用数值模拟方法,基于低负荷工况下汽轮机末级运行性能的深入分析,着重研究探... 构建以新能源为主体的新型电力系统,对燃煤发电机组深度调峰和超低负荷运行提出了越来越严苛的要求,进而对汽轮机组低负荷安全运行提出了越来越严峻的挑战。采用数值模拟方法,基于低负荷工况下汽轮机末级运行性能的深入分析,着重研究探索了不同解决方案在超低负荷工况下的工作机理与优化效果。研究发现,当机组从中低负荷下降到超低负荷时,末级叶片附近出现间隙涡、回流涡和分离涡等涡群,其范围随着负荷的减小逐渐扩大。低负荷工况降低机组背压和低压缸切缸运行是弱化汽轮机涡流、提高末级性能的有效途径,二者结合使用效果更佳。例如,在20%热耗率验收(THA)工况条件下,将背压从4.9 k Pa降低到2.5 k Pa,使得末级涡群影响范围明显减小,转子叶片转矩从–38 N·m增加到73N·m,末级运行性能明显改善。在10%THA工况下,采用降低背压和低压缸切缸相结合可使叶顶间隙涡完全消失,回流涡和分离涡的径向长度都减小50%以上;优化后的动叶转矩增加了约130 N·m,末级运行性能改善效果显著。 展开更多
关键词 汽轮机 低负荷工况 涡流 背压 切缸
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一次有台风影响的广元市中东部暴雨过程分析
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作者 黄亚林 孙美玲 王璐思 《科技创新与应用》 2024年第27期111-114,共4页
利用地面自动站降水资料、MICAPS高空实况资料、雷达资料和数值预报资料,对2019年7月19日广元市中东部出现的一次暴雨天气过程进行分析。结果表明,暴雨过程期间,受高空低值系统和低层暖湿气流的共同影响,同时伴随有台风活动,低层水汽条... 利用地面自动站降水资料、MICAPS高空实况资料、雷达资料和数值预报资料,对2019年7月19日广元市中东部出现的一次暴雨天气过程进行分析。结果表明,暴雨过程期间,受高空低值系统和低层暖湿气流的共同影响,同时伴随有台风活动,低层水汽条件和能量条件充沛。台风在此次过程中的作用,一是阻挡高空低值系统的东移,使影响系统较长时间维持在暴雨区;二是台风北侧偏东风气流将大量水汽源源不断向暴雨区输送。低涡切变线有利于水汽的辐合上升,在不稳定的暖湿大气层结中,地面弱冷空气入侵触发不稳定能量的释放。雷达特征显示广元市中东部为明显的片状混合云回波,中心回波强度超过45 dBZ,与强降雨中心落区一致。此次过程数值预报对形势的预报较为准确,对量级预报也有较好把握,但对落区预报较实况存在一定偏差,仅具有一定的参考价值。 展开更多
关键词 暴雨 台风 雷达回波 低涡切变线 数值预报
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动力电池测试用高低温试验箱温度场分析与流场模拟优化
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作者 郑晓腾 刘金平 《制冷学报》 CAS CSCD 北大核心 2024年第2期119-126,共8页
以试验区置有两个动力电池的294 L高低温试验箱作为研究对象,通过CFD模拟了高低温试验箱恒温45℃时箱内电池的温升和散热情况,并对高低温试验箱的流场进行优化。结果表明:对于同侧上送风下回风的气流组织形式,在试验区上部放置多孔板进... 以试验区置有两个动力电池的294 L高低温试验箱作为研究对象,通过CFD模拟了高低温试验箱恒温45℃时箱内电池的温升和散热情况,并对高低温试验箱的流场进行优化。结果表明:对于同侧上送风下回风的气流组织形式,在试验区上部放置多孔板进行孔板送风有助于提高流场均匀性;两个动力电池之间会出现涡旋现象,通过增加置物架与内箱底部的间距、适当增大回风口截面积均能减轻甚至消除涡旋现象,提高流场均匀性,当置物架与内箱底部的间距增至0.2 m,回风截面的高度增至0.15 m后,试验箱流场的整体不均匀度由1.73降至0.4,电池间的涡旋现象消失。 展开更多
关键词 动力电池 高低温试验箱 流场 涡旋
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