Comprehensive simulation of snow crystal deposition and electric field characteristics of composite sheath improved porcelain cantilever insulator in a wind and snow environment

The installed porcelain insulators on existing railway lines in China are prone to“snow flash”in winter.In order to prevent the occurrence of“snow flash”and improve the reliability of the insulators,a composite-porcelain insulator is designed.A multi-physics coupling simulation model is built based on numerical simulation methods of the electromagnetic field theory and computational fluid dynamics.Taking average electric field intensity on the surface of the insulator as the characteristic parameter of the electric field distortion degree and the snow crystal collision coefficient and distribution coefficient as the characteristic parameter of snow crystal deposition,the characteristics of snow crystal deposition under different wind speeds and wind direction angles and the electric field characteristics under two snow cover types are analyzed.The simulation results show that the average electric field intensity of composite-porcelain insulators is 10.4%and 13.8%,respectively,lower than that of porcelain insulators in vertical and horizontal wind snow covers,which can effectively reduce the degree of electric field distortion.The collision coefficient of snow crystals on the surface of the composite-porcelain insulator sheds is 16.0%higher than that of the porcelain insulator,and the collision coefficient of the trunk and the fittings are lower 20.2%and 11.9%than that of the porcelain insulator.There is almost no change in the distribution coefficient of the insulator sheds.

A Review of Thermo- and Diffusio-Phoresis in the Atmospheric Aerosol Scavenging Process. Part 2: Ice Crystal and Snow Scavenging

The role of phoretic forces in the identification of particles acting as ice nuclei in mixed phase cloud is discussed. A method used to identify the effective ice nucleating particles is to sample ice crystals, which are afterwards sublimated, and to examine the particles remaining after evaporation. The procedure takes into account only crystal with a maximum diameter of 20 μm, by assuming that small crystals do not scavenge aerosol during growth, and therefore that crystals contain only the effective nucleating particles. This assumption is questionable, however, as experiments have shown that even small ice crystals can scavenge aerosol. Another approach has been to compare the number and elemental composition of residual particles in small ice crystals and of aerosol near the cloud. By considering as example soot and black carbon aerosol, contradictory conclusions on their importance in the processes of ice nucleation have been reported in the literature. We suggest that, in addition to physico-chemical properties of soot/carbon aerosol particles, even the microphysical and environmental parameters involved in the transition of aerosol from gas phase to ice crystals in cloud should be considered. The contribution of phoretic forces should also be considered. After initial growth ice crystals can continue to grow by water vapour diffusion. Laboratory experiments confirm the contribution of diffusiophoresis with Stefan flow in the scavenging by snow crystals up to 3 mm in diameter. The particle scavenging efficiency of snow crystals is related to crystalline shape and depends on air relative humidity and temperature.

Sensitivity of Snowfall Characteristics to Meteorological Conditions in the Yeongdong Region of Korea

This study investigates the characteristics of cold clouds and snowfall in both the Yeongdong coastal and mountainous regions under different meteorological conditions based on the integration of numerical modeling and three-hourly rawinsonde observations with snow crystal photographs for a snowfall event that occurred on 29−30 January 2016.We found that rimed particles predominantly observed turned into dendrite particles in the latter period of the episode when the 850 hPa temperature decreased at the coastal site,whereas the snow crystal habits at the mountainous site were largely needle or rimed needle.Rawinsonde soundings showed a well-defined,two-layered cloud structure along with distinctive wind-directional shear,and an inversion in the equivalent potential temperature above the low-level cloud layer.The first experiment with a decrease in lower-layer temperature showed that the low-level cloud thickness was reduced to less than 1.5 km,and the accumulated precipitation was decreased by 87%compared with the control experiment.The difference in precipitation amount between the single-layered experiment and control experiment(two-layered)was not so significant to attribute it to the effect of the seeder−feeder mechanism.The precipitation in the last experiment by weakening winddirectional shear was increased by 1.4 times greater than the control experiment specifically at the coastal site,with graupel particles accounting for the highest proportion(~62%).The current results would improve snowfall forecasts in complicated geographical environments such as Yeongdong in terms of snow crystal habit as well as snowfall amount in both time and space domains.

A New Technology Study on the Production of Snow Salt

1 Introduction Snow salt is one of the multi-salt with highly added value,in named for its snowflakes structure appearance.In the present situation,the stacking density gap between different commercial snow salt is big,mainly ranged from700 kg/m3to 800 kg/m3.The competition in the market

雪晶成核和生长机理研究

在自然界 ,雪晶的形成是一个非常复杂的过程 ,要经历成核、生长、融并等阶段。探索雪晶的成核和生长机理对人工造雪技术的发展具有重要的作用。雪晶的形态是由冰晶的晶格结构和雪晶的生长环境所决定的。通过对均相成核和异相成核过程中自由能变化的分析 ,确定了晶核形成所需的临界半径和成核势垒 ,为研究晶核的形成过程提供了理论依据。依据雪晶质量生长率与水蒸汽通量之间的关系 。

冰雪晶碰并勾连增长的实验与观测分析

冰雪晶碰并勾连成雪花或雪团的过程是降水的重要机制之一。冰雪晶形态不同导致各类晶动力特性的差异,因此,无论从理论、数值试验还是室内模拟研究这一过程都有很大困难。该文就室内、外场试验和自然云的观测,讨论分析其发生机理和条件。结果表明:冰晶的增长过程有一个与云滴碰并增长相似的加速过程,冰晶碰并过冷滴形成霰(雹胚),凇附长成冰雹;冰雪晶相互碰并勾连、攀附增长为雪花或雪团,都是降水质点加速增长的重要过程。此过程仅在水面饱和、过饱和条件下发生,而水面欠饱和、无液滴(无云)时,冰晶很薄、晶型简单,无碰并勾连、攀附现象。冰晶在液滴存在的云雾中伴随气流对流、乱流运动中接触碰并勾连成雪花或雪团,其碰并勾连效率既受晶体形状影响,亦受晶体表面附着力的影响,其机制有勾连亦有粘连,晶型多样,以相同晶型为主,温度范围广(-3^-17℃);其中-13^-17℃碰并勾连效率最高,该层的枝、星状晶是勾连、攀附的主要区域,亦为冰晶繁生的主要区域、生长率最快,是人工增雨播撒人工冰核催化效率较高的温度段。

冰（雪）晶生长微物理过程的风洞实验研究

本文概要介绍了：（１）风洞实验研究的科学意义及应用前景；（２）冰（雪）晶增长微物理实验研究的概况；（３）新研制的冰（雪）晶增长小型垂直过冷云风洞及其测试系统；（４）主要实验研究结果，包括风洞实验模拟出的冰（雪）晶，含水量对冰雪晶增长的影响，风洞中冰（雪）晶运动方式、初始晶胚特性及运用实验结果指导气象灾害及其防治等。

双参数微物理方案在WRF单柱模式中的模拟检验和对比研究

利用耦合Milbrandt 2-mon(MY)和Morrison 2-mon(MOR)两种双参数微物理方案的WRF中的单柱模式,对TWP-ICE(Tropical Warm Pool International Cloud Experiment)试验期间的个例进行数值模拟。通过与观测资料和云分辨率模式的模拟结果进行对比发现:两种双参数微物理方案能较好地模拟出TWP-ICE期间热带云系的宏观和微观的特征。模拟的降水率、地表向下长波辐射和大气顶向外长波辐射的量级、时间演变趋势与观测相一致;总的液相和冰相水凝物的垂直分布以及随时间的演变特征总体与观测以及云分辨率模式的结果也较接近。在整个时期,两种方案水云中的雨滴宏观和微观特征差异较小,而云滴混合比在两种方案之间的差别显著;冰晶对冰云的贡献在MY方案中占据主导地位,而MOR方案中雪在冰云中扮演的角色相比于在MY方案中更为重要。微观上与MY方案相比,MOR方案中的云滴是由数量更大的小云滴构成,但冰晶却是由数量较少的大冰晶粒子构成。微物理过程转换率的区别是造成两种方案冰云宏观分布特征差异的主要原因。与冰晶和雪有关的微物理过程转换分析表明:活跃期两种方案中与冰晶有关的主要微物理转换项有冰晶的凝华增长、冰晶向雪的自动转化、冰晶被雪碰并以及冰晶的沉降过程。而雪主要的转换项包含沉降和凝华过程等,其中MY方案中雪的主要转换项更为丰富。该时期两种方案冰晶和雪的主要微物理转换项的垂直分布以及量级特征的差异同冰云的宏观分布相一致。季风抑制期,两种方案中冰晶主要的源汇项包括凝华增长和沉降过程。MY方案中凝华凝冻核化也是主要的源汇项之一。抑制期MOR方案中高空的雪发展较强,参与的微物理过程较MY方案更为丰富,主要转换项比MY方案高出约一个量级。

雪晶形成过程与人工造雪机技术

本文从自然降要过程出发 ,介绍了自然雪晶的形成过程、条件和成长机理 ,进而阐明了实现人工造雪过程所需要的基本条件和要求 ,对目前存在的人工造雪机进行了分类机理说明 。

雪晶成因及人工造雪分布类型探讨

从雪晶成核和生长两个方面深入探究了雪晶成因机理,讨论了影响雪晶形成过程中各种作用因素,分析总结了人工造雪分布类型和及其相关的影响因素。对于造雪技术的进一步扩展,以及合理规划滑雪项目,具有较为重要的指导意义。

雪晶生成过程机理

雪花的形成包括晶核的形成和雪晶的生长两个阶段。晶核是雪晶形成的关键 ,冰晶的分子结构决定了雪晶的六角对称形状 ,生长环境的温度和湿度是影响雪晶生长和形状的主要因素。实验研究表明 ,碘化银微粒对雪晶的形成具有极好的促进作用 ,雪晶的生长是一个非常缓慢的过程。

雪花盐生产新工艺研究

研究了雪花盐生产新工艺,在结晶饱和卤水温度82℃、饱和卤水进水温度60℃、溢流流量2.5×10-3m3/h、控淋时间为48h的工艺条件下,测得雪花盐的堆积密度为440kg/m3。分析了该工艺生产雪花盐的结晶机理。实验所得雪花盐结晶产品片晶结构好、堆积密度小。

自然冰雪晶粒子观测及形状分类研究进展

冰雪晶是云中水成物的重要组成部分,鉴于不同形状的冰雪晶形成及增长的物理条件、过程经历不同,为此准确判断观测冰雪晶粒子的形状是揭示云微物理结构和降水机制的重要依据。文中概述了近半个多世纪以来中外观测冰雪晶粒子的方式和手段。梳理了对冰雪晶粒子的测量和形状分类技术的发展历程。分析总结了冰雪晶观测及其形状分类识别技术的新进展,并对未来发展进行了展望。旨在促进和推动以冰雪晶形状为基础的中国云微物理结构与降水机制的深入研究。

双制冷温度双工质吸收制冷系统Ⅱ的模拟

为克服在较高温度的热源下只用氨作为制冷剂时采用二级再生流程系统操作压力高的弊病 ,提出了一种新的吸收制冷系统。将水 -溴化锂和氨 -硝酸锂二系统耦合 ,在后者所组成的系统 2中设置二个不同蒸发温度的蒸发器。对该系统的操作性能进行了热力学模拟 ,分析讨论了热源温度、冷却水温度和低温蒸发温度的影响及系统适宜的操作条件。在较高的热源温度和较宽的操作条件下 ,系统操作性能稳定 ,其制冷性能系数COP可以稳定在 0 .95以上 ,稍低于类似条件下只用水 -溴化锂作为工质的二级再生系统 ,但相应的制冷温度分别为 1℃和 - 5℃ ,是一种很有实用价值的吸收制冷系统。

南极冰雪晶的形态分析

1985年11月～1987年1月中国第二次南极考察期间,在长城站设立了冰雪晶观察点,对长城站区全年的雪情进行了监测。共捕捉到6次与冰雪晶有关的降雪过程,收集到4大类19个亚类的303张不同晶形的冰雪晶显微照片。对这些样片的时间序列分析表明,长城站上空云体中具有泡状结构,过冷水密度也存在某种分布。

人工造雪技术研究进展

为推动我国冰雪事业发展,提升人工造雪技术水平,保障冬奥会各滑雪项目比赛顺利举办,综述了人工造雪雪晶产生机理及人工造雪机的发展,分析了国内外主要的人工造雪机类型,即压缩空气型造雪机,风扇型造雪机,碎冰型造雪机,为今后研究新型人工造雪技术提供理论基础。

整车热力学风洞试验室降雪设备和试验方法的研究

本文采用高压冷水和压缩空气结合的方式在整车热力学环境风洞试验室中实现了人工造雪的功能。从自然界降雪形成原理,研究在环境风洞中实现人工降雪的管路和系统设计以及试验方法。最终试验结果表明,可在环境风洞中实现连续、稳定的降雪。该降雪类似于自然界中的真实降雪,较为蓬松。

基于元胞自动化模型的三维雪花晶体近似模式的产生(英文)

关于雪花生长过程的计算机模拟已经受到了广泛关注.其中,元胞自动化模型是一种基于网格和简单规则的计算方法.尽管这是一种简单的模型,但其在模拟复杂过程(比如:生命现象,晶体生长和湍流)时往往能取得较好的结果.提出了一种由传统的二维模型扩展而来的三维雪花晶体生长方法.计算机模拟结果显示提出的方法能够更精确地模拟出三维雪花的晶体化过程.