Spiral rainband in a numerically simulated tropical cyclone

Spiral rainband is a prominent structure of tropical cyclone. Though its forming mechanism, vortex Rossby wave theory, has been widely accepted in recent years,its internal structural features are still not well known. The spiral rainband in the severe tropical storm Kammuri (2002),which caused heavy rainfall in southeast China, is simulated using the mesoscale model MM5 (V3). Results show that the simulated spiral rainband propagates azimuthally at a speed close to that of vortex Rossby wave in theory, and is accompanied with energy dispersion in the radial direction. The structural features of simulated spiral rainband are analyzed with the high-resolution model output including the full physical process. Positive vorticity, ascending motion, horizontal momentum and so on are highly concentrated in the spiral rainband. The convergent moisture of spiral rainband comes mostly from the planetary boundary layer under 1 km.Airflow from the outside of spiral rainband is convective instability, which can provide instability energy for convection development. However, the atmospheric stratification in the inside of spiral rainband is neutral, implying that the instability energy has been released. There is a mesoscale strong wind band just near the spiral rainband in the outer side with a maximum wind speed exceeding 30 m/s, which results from the pressure force acceleration when the air flows into the spiral rainband along the gradient of pressure.     

城市街道内污染物扩散的数值模拟

随着我国城市汽车保有量的迅速攀升,城市中心区的空气质量与生态环境急剧恶化.利用CFD数值模拟研究街道峡谷污染物的扩散问题,对比分析了开放街道峡谷和城市街道峡谷污染物的扩散问题,证明了计算域和入流边界处湍动能k和湍动能耗散率ε取值的重要性.计算结果与经典风洞实验符合很好,证实了相同条件下城市街道峡谷的背风墙和迎风墙上的污染物浓度均大于开放街道峡谷的相应值.利用3维建筑群计算实例,指出了寻求建筑群优化布局对减小小区污染的重要性.     

磁化等离子体中的涡旋湍流和反常扩散

研究磁化等离子体中短波漂移阿尔芬波涡旋结构．采用涡旋气体动力学模型，估计出等离子体涡旋湍流谱，并求出反常扩散系数．研究结果表明，涡旋湍流产生的反常扩散系数与扰动场振幅的平方根成正比．     

高TC超导体的涡旋相结构与超声衰减关系研究

根据Fisher的超导涡旋玻璃相理论,提出了高温超导体混合态超声衰减的涡旋形态模型．论述了高温超导体混合态复杂的相结构,给出了各向异性高温超导体的混合态相图．概括出超声衰减两种类型：钟型(衰减较缓慢)与λ型(衰减较迅速),并且揭示相应的相结构及其特点．同时指出：在温度比超导临界温度低的情况下Pankert超声波与涡旋线相互钉扎机制较为适用,在温度较超导临界温度高的情况,涡旋线相变模型较为适用．     

中国东部地区一个中尺度对流涡旋的涡度收支分析

中尺度对流涡旋(MCV),与其他中尺度涡旋不同,有着其独特的动力机制与发展途径.一旦MCV形成,极易产生灾害性天气过程.为了解我国的MCV,使用非静力中尺度模式天气预报和研究模式对中国东部2003年7月4至5日降水过程进行了高分辨率的双向三重嵌套的数值模拟.与观测资料比较,模拟结果较为准确地再现了当时的大气状况.采用了空间滤波的方法对模式结果进行了大尺度背景场与中尺度扰动场的尺度分离,对MCV的结构与移动进行分析,并追随MCV的活动对其的涡度收支情况进行诊断分析.分析表明,大尺度背景场与中尺度扰动场对MCV的作用有着明显的差异.MCV的移动由大尺度背景风场引导;其中辐合作用直接决定了MCV的形成与发展,大尺度水平运动对中尺度涡度的水平输送为水平平流项的主要部分.而由垂直风速的水平变化所导致的水平涡度的倾斜作用在此MCV形成与发展阶段作用并不明显.成熟时的MCV与成熟时的中尺度对流复合体类似有着3个明显的环流,在对流层高层与低层均为辐散反气旋性环流,对流层中层则为较为深厚的气旋性环流.     

应用格子Boltzmann方法模拟街道峡谷内的流场

用格子Boltzmann方法模拟了入口速度u0=0.1的对称以及不对称街道峡谷内不同时刻的流场,从模拟结果可以看出街道峡谷内一个逆时针漩涡的形成过程,与传统方法的模拟结果相比,具有很好的一致性,从而说明用格子玻尔兹曼方法模拟街道峡谷流场是完全可行的.     

Numerical simulation of Meiyu front and the diagnosis of moist vorticity vector

Moist vorticity vector is introduced to study the development and evolution of mesoscale convective vortex (MCV) in the Meiyu front precipitation with the Advanced Regional Predication System (ARPS). In this study, the heavy rainfall is simulated to investigate the genesis, development and dissipation of middle scale convective vortex, which occurred from 0000 UTC 3 July to 1200 UTC 5 July over the Jianghuai River valley. Moist vorticity vector (MVV) has zonal, radial and vertical components in its 3D spatial distribution. The simulation shows that the vertical component of moist vorticity vector well demonstrates the spatial distribution characteristics of middle scale convective vortex, especially in the process of Meiyu front precipitation. Diagnosis upon zonal, radial averaged and mass-integrated quantities of MVV shows that its vertical component and the surface precipitating ratio are in phase with a correlation coefficient of 0.68, indicating that the vertical component of MVV is closely associated with the Meiyu front precipitation. In addition, the tendency of the vertical component of MVV is mainly determined by the interaction between the vorticity and the zonal and radial gradient of condensational or depositional heating.     

椭圆齿轮流量计使用注意事项及常见故障处理

阐述了椭圆齿轮流量计的计量原理,分析了常见故障产生的原因提出了解决方法。     

导叶式旋风管排气管内流动减阻的试验研究

通过对导叶式旋风管内流动参数的测量分析,发现排气管内气流旋转强度高,并存在“滞流”、“倒流”及逆压梯度等无益于颗粒分离的流动状态,造成排气管内压力损失约占旋风管总压降的22%。在排气管内安装框形结构后,可有效削弱和抑制上述耗能流动,在保证分离效率基本不变的前提下,使旋风管减阻幅度达到9%。     

多项式拟合的通用QBASIC程序及其在气相色谱分析中的应用

按照多项式拟合的数学方法，提供了QBASIC语言编写的通用求解程序，给出了程序设计思想和主要模块的流程图．举例说明程序在气相色谱分析中对转子流量计校正的应用．