Renormalized numerical simulation of flow over planar and non-planar fractal trees

We review the fundamentals of a new numerical modeling technique called Renormalized Numerical Simulation (RNS). The goal of RNS is to model the drag force produced by high Reynolds-number turbulent flow over objects that display scale-invariant properties, objects such as tree-like fractals. The hallmark of RNS in this application is that the drag of the unresolved tree branches is modeled using drag coefficients measured from the resolved branches and unresolved branches (as modeled in previous iterations of the procedure). In the present paper, RNS is used to study the effects of branch orientation on the drag force generated by highly idealized trees in which trunk and branches have square cross-section, and the branches all lie in a plane perpendicular to the incoming flow. Then, the procedure is generalized to the more general case of non-planar branch arrangements. Results illustrate that RNS may enable numerical modeling of environmental flow processes associated with fractal geometries using affordable computational resolution.     

离体培养植物细胞的表面与细胞粘连

对离体培养的胡萝卜（Ｄａｕｃｕｓｃａｒｏｔａ）细胞和普通烟草（Ｎｉｃｏｔｉａｎａｔａｂａｃｕｍ）细胞的表面进行了扫描电镜观察．观察表明，细胞的自由表面上有很多疣突和纤丝．疣突的大小不同、形状各异，主要含果胶质；有些细胞表面出现小坑，坑中集中有许多微小颗粒．疣突相互可融合成更大的疣突或连成桥；纤丝常与疣突结合．纤丝－纤丝的交织，纤丝－疣突的交联，及疣突－疣突的融合，在细胞壁外表面构成交织的网络．同种细胞之间及异种细胞之间均可通过纤丝、疣突的交织融合而粘连．疣突分布不均一，且与细胞的分散性有关．与疏松烟草愈伤组织比较，致密烟草愈伤组织细胞的自由表面上疣突显著较多．在分化再生时，烟草愈伤组织首先致密变绿，然后才见到芽的分化及植株再生．对疣突出现、壁物质沉积与细胞粘连、细胞分化、形态建成几者之间的关系进行了讨论．     

污水海洋处置工程多喷口浮射流近区稀释扩散规律研究

结合上海市污水治理二期工程稀释扩散物理模型试验，首次通过量纲分析的方法，对上升管上布置多个喷口时污水的近区稀释扩散规律进行了研究，得出了上升管布置不同喷口个数时的近区稀释度计算公式，所得公式具有一定的适用性，这对于我国较浅水域扩散器的设计具有重要的指导意义。     

黄河三角洲附近海域浮游植物多样性

以文献资料和定性调查结果，综合分析了黄河三角洲附近海域浮游植物物物种多样性；以１９９６年定量调查资料，研究了浮游植物多样度以及与均度、单纯度之间的关系。结果表明：该海域共鉴定出浮游植物７２种，占本海域已记录浮游植物１１６种（变种）的６２％，分占中国海和渤海已记录种类的５％和１９％；浮游植物多样度在０．１９～２．１０之间，均度在０．２７～０．９７之间，单纯度在０．１４～０．９１之间；多样度与均度呈显     

未来十年国内精密锻造技术展望——第一届全国精密锻造学术研讨会综述

通过对第一届全国精密锻造学术研讨会概况的介绍 ,就目前国内精密锻造的发展态势进行了总结 ,并对未来十年精密成形技术作了展望。数值模拟和物理模拟同等重要 ,文中对闭塞锻造等成形新工艺在汽车零件制造中的应用寄予厚望     

Enhanced solar still productivity using transparent walls with an integral trough and organic porous absorber material

This experimental work has been conducted to compare the performance of the modified stills with that of the conventional still. Three modified stills (S1, S2, and S3) and conventional still (S4) were fabricated, each with 0.5 m² of the basin area. S1 and S3 had transparent double glass walls with air in between acting as insulation, whereas S2 has a single transparent wall. S4 has insulated plywood walls painted black from inside. A mixture of coco peat and charcoal was used in S1, S2, and S3, whereas there was no basin material for S4. Experiments were conducted by changing the water quantity in the solar still ranging from 5 to 10 kg. Maximum distillate output of 5.46 l/m²-d was obtained for S2, whereas it was 3.80 l/m²-d for S4 for an average solar radiation intensity of 675 W/m² (24.3 MJ/m²-d). Use of transparent walls with troughs to collect condensate increased the condenser area by 78.4%. The distillate water cost per liter was estimated as Rs. 0.86 (0.013 US$) and Rs. 1.61 (0.025 US$) for S2 and S4, respectively. Energy payback time for S2 was estimated as 4 months. Theoretical and experimental values showed that there is a significant loss of incoming solar radiation due to wall shadow.     

明渠中有机质微粒沉降过程的随机游走模拟

基于明渠流动的主要特点,考虑紊动强度的垂向非均匀性,及颗粒运动的游荡效应（loitering effect）影响,对微粒运动基本方程进行改进,建立了明渠非均匀紊流中考虑游荡效应的随机游走模型,对明渠中微粒的沉降损失进行了模拟分析.模拟结果显示,不考虑游荡效应影响时,明渠中微粒的沉降损失率可用微粒沉速与水深之比计算;而在游荡效应影响下,微粒沉降损失率会发生约18%~27%的下降,下降百分比与均匀紊流中微粒沉速在游荡效应影响下的折减百分比渐近值（19~25%）基本一致.本文结论基于不考虑微粒重悬浮、游荡效应为紊流对微粒沉降的主导影响机理等前提,主要适用于对明渠中细小有机质微粒沉降至床底过程更准确的计算分析.     

海洋平台主机烟气排放对直升机影响数值分析

目的确保南海A钻采平台直升机安全起降,直升机全年不可用概率控制在10%以内。方法通过Fluent软件数值模拟多工况、多风向风速下高温烟气在直升机甲板上方及周围空间的流动、温升及湍流分布规律,以CAP43-7标准所推荐直升机起飞和降落的安全原则为判定依据,分析计算温升和湍流对直升机起飞和降落的全年影响概率。结果综合得出直升机不可用概率理论值,M1工况为8%,M2工况为9%。结论模拟计算结果为平台主机烟管及直升机甲板布置方案的确定提供理论依据,为平台直升机起降操作起到指导作用。     

天津一次雾-霾天气过程的近地层温湿结构和湍流特征分析

采用地面大气能见度、PM_(2.5)质量浓度、梯度气象资料、塔上湍流观测资料等多种资料及后向轨迹方法,分析近地层温湿结构和湍流特征对2016年12月16日—21日天津地区一次严重持续雾霾天气演变过程的影响.结果表明,本次雾霾天气过程可以明显的分为霾、雾的生成和发展、雾成熟和雾霾消散等4个阶段,近地层温度、相对湿度和风的垂直分布及湍流特征对各阶段的雾-霾转化起到了重要作用.霾生成期间,偏南气流盛行,地面风速降低,RH不断增大,湍流不活跃;地面辐射降温引发了近地层内显著的强逆温,并导致RH由地面到高空逐渐增大,有利于雾的生成和发展;感热通量和潜热通量爆发式增长,导致逆温层瓦解,雾顶继续抬升,雾进入成熟阶段,湍流活动减弱;受西北气流影响,湍流活跃,高空的干冷气团向下取代地面暖湿气团,结束本次雾霾天气过程.采用近地层温湿结构和湍流特征资料,可用于雾-霾天气的演变及其转化过程精细分析.     

波纹微通道湍流促进器减缓SFMBR的膜污染效果分析

主要通过浸没式平板膜生物反应器的膜污染阻力分布和膜表面的污染特性来分析波纹微通道湍流促进器减缓浸没式平板膜生物反应器的膜污染效果.结果表明,波纹微通道湍流促进器有效地降低了总阻力Rt,降低率达到68.01%,其中的Rrf、Rc和Rp+Ra分别降低54.20%、87.98%和84.00%;滤饼层厚度、有机和无机污染成分都减少,且污染层更易去除.综合膜污染阻力分布和膜表面污染物表征结果从扰流作用强化机理、逆扩散机理、絮凝机理和微孔强化过滤机理四个方面分析了波纹微通道湍流促进器减缓浸没式平板膜生物反应器膜污染的效果.