Buckling Properties of Water-Drop-Shaped Pressure Hulls with Various Shape Indices Under Hydrostatic External Pressure

The water-drop-shaped pressure hull has a good streamline,which has good application prospect in the underwater observatory.Therefore,this study conducted analytical,experimental and numerical investigation of the buckling properties of water-drop-shaped pressure hulls under hydrostatic pressure.A water-drop experiment was conducted to design water-drop-shaped pressure hulls with various shape indices.The critical loads for the water-drop-shaped pressure hulls were resolved by using Mushtari’s formula.Several numerical simulations including linear buckling analysis and nonlinear buckling analysis including eigenmode imperfections were performed.The results indicated that the critical loads resolved by Mushtari's formula were in good agreement with the linear buckling loads from the numerical simulations.This formula can be extended to estimate the buckling capacity of water-drop-shaped pressure hulls.In addition,three groups of pressure hulls were fabricated by using stereolithography,a rapid prototyping technique.Subsequently,three groups of the pressure hulls were subjected to ultrasonic measurements,optical scanning,hydrostatic testing and numerical analysis.The experimental results were consistent with the numerical results.The results indicate that the sharp end of the water-drop-shaped pressure hulls exhibited instability compared with the blunt end.This paper provides a new solution to the limitations of experimental studies on the water-drop-shaped pressure hulls as well as a new configuration and evaluation method for underwater observatories.

Evolution of a Water Pendant Droplet: Effect of Temperature and Relative Humidity

As part of a better understanding of drying liquids within porous materials, measurements from 293 to 343 K of deionized water surface tension in air as a function of relative humidity are exposed. Experimental work was carried out using the pendant drop method coupled with image analysis within an adapted instrumented climatic chamber. Results show that surface tension linearly decreases when relative humidity increases. Although the effect of humidity is less compared to that of the temperature and even less compared to a surfactant impact, it must not be neglected and values have to be mentioned when dealing with water evaporation. Modifying surface tension also affects the pendant drop shape. The drying kinetics of the pendant drop volume and its outer shell are connected to this change of shape. Steam in the air can be assimilated to a wetting agent, hence a surfactant, and can be used in an environmental-friendly way to ease the drying stage. Indeed, the challenge is to limit the risk of cracking and damaging pieces during this crucial step in material processing.

The corrosive behaviors of GI and IF steel sheets in salt water drops

The corrosive behaviors of hot-dip galvanized steel （G I） sheets and the corresponding interstitial free （IF） steel base sheets for use in automobiles were investigated by the classical salt water drop （SWD） test at room temperature. The corrosive processes and products were observed and analyzed through morphological observation, a scanning electronic microscope （SEM） and an energy dispersive spectrum （EDS）. The results show that the anodic and cathode sites can be distinguished clearly during and after the test. The propagation of rusting, and the color, distribution and composition of the final corrosive products of the two kinds of materials are quite different. The SWD corrosive mechanisms of steel with and without galvanized coating are both discussed in this paper.

Rear-Surface Deformation of a Water Drop in Aero-Breakup of Shear Mode

Deformation of water drops in shock-induced high-speed flows is investigated with a focus to the influence of primitive flow parameters on the rear-surface deformation features. Two typical deformation patterns are discovered through high-speed photography. A simple equation to evaluate the radial acceleration of the drop surface is derived. The combined use of this equation and outer flow simulation makes it possible for us to reconstruct the profiles of the early deformed drops. The results agree well with the experiments. Further analysis shows that the duration of flow establishment with respect to the overall breakup time shapes the rear side profile of the drop. Thereby the ratio of the two times, expressed as the square root of the density ratio, appears to be an effective indicator of the deformation features.

Study on Pre-treatment of the Domestic Sewage by Water-dropping Aeration Zeolite Bed Technology

[ Objective] The research aimed to study pre-treatment effect of the domestic sewage by water-dropping aeration zeolite bed technology. [ Method] By water-dropping aeration manner, we conducted sewage reoxygenation. Zeolite was used to replace traditional contact oxidization fill- er. We inspected oxygenation effect of the water-dropping aeration manner and removal efficiency of the pollutant in sewage after biological contact oxidation. [ Result] Under the experimental condition with water-dropping heights of 0.30, 0.45 and 0.60 m, average added values of the dissolved oxygen for raw water were respectively 2.4, 3.6 and 4.2 rag/l_ after water-dropping aeration. Under the situation with average HRT of 2 h, when COD, TN and TP of the influent were respectively 309.0 -464.0, 33.3 -95.0 and 4.0 -7.5 mg/L, their corresponding average removal rates were 47.25%, 46.39% and 40.75%. [ Conclusion] The research conducted useful attempt for high-efficiency and low-cost treatment of the domestic sewaqe in rural area.

A Comparative Study of Water Imagery in the Chinese Poem Happy Rain on a Spring Night and American Poem A Drop Fell on the Apple Tree

This essay directs at the water imagery of two poems Happy Rain on a Spring Night and A Drop Fell on the Apple Tree.Although living in different time and place, Chinese poet Du Fu and American poetess Emily Dickinson share some deep understanding of the water. This secret of water imagery is unveiled in this essay with the help of Archetypal Criticism, revealing its significance to the human beings as a race.

基于蜂窝仿生流场的质子交换膜燃料电池的性能研究及优化

为了增强质子交换膜燃料电池(PEMFCs)内部燃料分布的均匀性与水管理能力,本文研究了一种新型的基于仿生结构的蜂窝仿生流场。首先,根据蜂窝结构特征,搭建出三维多相流非等温几何模型并确立PEMFC的数学模型;其次,采用计算流体动力学Fluent软件对模型进行无关性与有效性验证,并对蜂窝仿生流场和常规平行流场的电池性能和燃料分布进行了模拟分析;最后,对比极化性能、气体流速分布、燃料与液态水组分浓度和电流密度分布,验证了蜂窝仿生流场设计的有效性。研究结果表明:采用蜂窝仿生流场的电池峰值功率密度比常规平行流场高15.6%,其内部水管理能力和燃料分布均匀性均强于平行流场;左端进气的蜂窝仿生流场比采用上端进气的蜂窝仿生流场在气体通路内具有更均匀的气体压力,可有效避免流道内产生局部涡流,其峰值功率密度可以达到0.3933 W/cm2。

Experimental study on steam-water two-phase flow frictional pressure drops in helical coils

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水滴形大跨钢屋盖结构风洞试验和风振分析

自然风经过大跨结构时,由于结构屋顶形状不规则,通常会引起柔性屋面的振动,因此针对大跨屋面结构抗风设计需要考虑风压分布和风振响应。以陕西省水务集团矿泉水生产车间为工程背景,制作了1∶200的刚性模型,通过刚性模型风洞试验测得该水滴型大跨钢屋盖结构的表面风压,研究了屋盖表面典型测点及整体的风压分布规律。基于风洞试验数据,对结构进行风振时程分析,得到了屋盖表面的风振响应和风振系数。结合刚性模型风洞试验和风振分析,深入研究了水滴形大跨屋盖结构的风压分布规律和风致振动特性,并总结了其共性规律。

水位骤降作用下浔江岸堤滑坡稳定性分析及治理方案研究

为研究水位骤降对滑坡稳定性的影响,以浔江三布堤滑坡为例,根据详细的现场勘察及水库运营资料,利用FLAC 3D有限差分岩土分析软件,对水位骤降条件下堤岸滑坡的稳定性进行模拟计算,从滑坡稳定性系数、滑动面及滑坡位移等方面分析,并结合现场勘察对该滑坡治理方案进行模拟。结果表明浔江水位从十年一遇洪水位(37.2 m)骤降至正常水位22.3 m后,堤岸滑坡稳定性系数从1.60降至0.81,由于水位快速持续下降引、诱发滑体失稳破坏;进行压石护坡治理后,水位骤降工况下堤岸滑坡稳定性系数从0.81增加到1.20,为滑坡治理提供了高效且低成本的治理方案。

某型飞机投水作动系统建模与同步性仿真分析

提高某型飞机投水舱门的同步性是保证灭火任务顺利完成的关键。为了开展多参数对收放作动筒同步性影响的研究工作,首先,基于投水灭火流程和投水作动系统液压原理,通过AMESim的液压元件库、逻辑库和状态机,建立了投水作动系统仿真模型。其次,通过连续投水工况仿真模拟,进行投水作动系统方案的功能性能分析,从而验证了仿真模型符合某型投水飞机工况性能要求。最后,通过批处理模式探究各敏感参数对多投水舱门收放作动筒的同步性影响。仿真表明:投水作动系统仿真模型可以实现多系统、多模式等不同任务和功能的仿真分析,电磁阀流量、负载、舱门作动筒活塞杆直径和管路直径对多缸同步性有着明显影响。

基于GWO-IWD算法的装配序列规划研究

针对复杂装配体装配序列规划问题,提出一种基于灰狼优化的智能水滴算法。综合考虑零件的属性特征及几何约束,构建装配体的装配信息模型,将装配成本作为优化的目标函数,以装配序列的几何可行性、装配方向改变次数以及装配工具改变次数为约束条件,建立面向装配体的优化模型。采用智能水滴算法对装配体优化模型进行求解,并利用灰狼优化算法来改善智能水滴算法的搜索能力,提高算法求解精度。以柱塞泵装配体单元为例,验证了该算法的可行性及有效性。

高原山地环境腹箱式灭火飞机投水数值模拟

为探究高原山地环境下腹箱式灭火飞机投水着水特性,基于VOF多相流模型构建了飞机投水过程仿真模型,分析地形坡度和海拔高度对地面落水分布的影响,并以投水有效利用率和有效水体覆盖厚度为指标评估其投水效能.结果表明,随山地坡度增加,相同飞行速度下落水地面分布的长度减小而宽度增加,落水区域前端水体分布更密集;随海拔高度增加,相同飞行速度下地面落水分布中后区域更连续,且高原环境下落水地面分布宽度增加但长度变化较小.此外,投水效能普遍随坡度的增加先降低后提高;投水有效利用率在小坡度时随海拔高度增加而提高,其他工况下受海拔高度影响较小,有效水体覆盖厚度普遍随海拔高度增加而降低.

大型梯级水电站枯水期多模式优化调度模型研究

针对大型梯级水电站枯水期调度面临的市场环境复杂、枯汛转换期来水形势多变等难题,提出了梯级水电站调度决策多模式自适应匹配方法,分别建立“无(消落)压力环境”模式和“有(消落)压力环境”模式下的优化调度模型,根据预报信息自动选择和灵活切换调度模式和目标,生成各电站水位动态控制和灵活调整策略。结果表明:“无(消落)压力环境”模式下可使流域发电量增加2.57%;“有(消落)压力环境”的“均匀突破”模式和“集中突破”模式下分别可增加发电量4.59%、5.32%,前者面临无法消落到位的风险更小,后者发电效益更大。该模型可有效降低枯水期消落和发电风险,提升流域整体发电效益,对于不同来水、发电等工况均表现出较好的适应能力和优化效果。

基于Fluent的球形托卡马克装置磁体的水冷结构设计

应用Fluent软件对SUNIST-2球形托卡马克磁体内部流动与传热进行了数值模拟,对磁体的水冷结构设计进行了优化。依据SUNIST-2特定的工作状态,分别对磁体水冷系统在多种流速及不同进口温度条件下的性能进行了仿真分析,对比了各条件下的冷却效能与压力降。模拟研究表明,基于数值模拟优化的磁体水冷结构方案,显著增强了磁体在实际运行状态下的稳定性与安全性。加工后的磁体水冷结构的压力降测试的实验结果验证了数值模拟的结论。

结冰气象探测飞行及数据符合性分析方法研究

结冰气象捕获、最优气象条件选取准则、符合性数据处理方法等一直是飞机自然结冰试飞过程中亟待攻克的难题。通过分析CCAR25部附录C结冰气象标准的形成背景及其局限性,提出一种利用结冰试验研究机开展结冰探测的飞行方法,该方法包括试验研究机的选型、改装、探测目标区域确定、飞行操作策略、飞行安全管理、数据处理等。依据对探测数据的统计分析,确定民用运输机自然结冰试飞的气象条件选取准则,规范云隙、液态水含量、总水收集率、积冰速率、积冰厚度和冰脱落程度等一系列结冰气象的数据处理方法和符合性判据,校验国内结冰气象预测算法,探索自然结冰试飞的安全管控策略和风险降解措施。大量飞行实测表明:该方法通用性强,效果显著,已经成功应用于C919大型客机合格取证试飞工作,并有力支撑了国内结冰适航标准自主。

渤海油田高效投捞无缆分注工艺研究及应用

针对无缆智能注水技术应用于油田开发中,其工艺存在无缆智能工作筒电路可靠性不足、电池寿命短造成无缆注水管柱寿命低的问题,提出了高效投捞无缆分注工艺。研发的井下可投捞无缆分注工作筒将无缆注水工作筒的电子元器件、传感器部件集成在可投捞注水芯子内部,利用钢丝作业实现芯子的快速维修、更换,有效地延长管柱寿命。同时研发了配套的地面发码系统与高效压力波控制编码技术,通过软件和硬件的配合,实现了水嘴开度调节、流量预设等7大功能,有效地提高了无缆调节效率。目前渤海油田现场应用62井次,投捞成功率达到100%,注水合格率达到97%以上。该技术的研发可为海上油田的高效智能注采提供新的选择。

基于智能水滴算法解决车辆路线问题

针对运输、分销和物流领域的重要优化问题——车辆路径问题(Vehicle Routing Problem,简称VRP),本文采用了智能水滴算法进行解决,通过对十四个基准VRP问题进行测试的计算结果分析,与其他几种元启发式方法进行了比较。

带气液调配蒸发器空气源热泵热水器的实验研究

气液调配蒸发器通过调整干度和质量流速实现传热性能提升。分别将两个管程布置为4-2-4-6-4(蒸发器1)和5-4-3-4-4(蒸发器2)的气液调配蒸发器用于热泵热水器中(分别为系统A和系统B)进行实验,并进行了对比研究。结果表明:相比于蒸发器1,蒸发器2制冷剂分布更均匀,且蒸发器侧压降减小了10.91%。在名义工况下,相比于系统A,系统B制热量减少1.69%,功率也减少1.45%,两个系统COP基本相同。系统B的排气压力比系统A小26.35~84.78 kPa,更有利于压缩机的安全运行;在不同的环境温度下,系统B的压缩机功耗均小于系统A,当环境温度为30℃时,系统B的性能比系统A提高了2.1%。

基于跌落仿真的热水器变形及问题改善

热水器产品在出厂前需要通过跌落测试等破坏性验证,以模拟产品在装卸运输过程中的跌落情况。文中以某热水器跌落产生的面壳和底壳的错位变形为例,对热水器进行了6面12棱8角共26个工况的仿真计算。通过对跌落后面底错位位移的分析,找出跌落错位最严重的工况。并以最严重的几个工况为例,判断出面底错位的原因为面盖挂钩设计不合理。通过对挂钩结构的修改,并打样验证,解决了该问题。通过对跌落过程实现仿真可视化,可以更直接地找到跌落失效的具体原因,该方法减少了方案验证的次数,缩短了研发周期,具有很好的推广价值。