导弹垂直发射出筒过程中通气空泡流研究

将通气空泡技术应用于导弹水下垂直发射出筒过程,通气空泡是高速航行体获得稳定空泡的一种重要技术。采用基于Mixture多相流模型的有限体积法求解RANS方程,结合动网格技术,对水下垂直发射导弹出筒过程的轴对称流场进行了数值模拟,研究导弹的流体动力特性和通气空泡的演化。结果表明通气空泡可减小导弹出筒过程中的阻力和改善导弹的流体动力载荷。     

潜射导弹出筒过程的三维非定常数值模拟研究

潜射导弹出筒过程的研究对其水弹道以及水下动载荷的计算具有重要的意义。本文采用多相流模型和动网格技术,求解非定常雷诺平均NS方程,对考虑潜艇平动影响的导弹冷弹射出筒过程进行了三维非定常数值模拟。三维数值模拟体现出筒口效应、发射气团现象等经典实验现象与实验符合较好,说明本文方法能够有效地揭示导弹出筒过程中多相流体间的相互作用以及相应的流体动力特性,通过分析这些现象中导弹所受冲击的形成机理,为工程应用提供有意义的参考。     

水下气体射流初期数值研究

本文提出了一种新的水下气体射流的数学物理模型，并成功地将位标函数方法应用于水下气体射流气水交界面求解，数值模拟了水下气体射流初期的流动演化和气水相互作用特性，得到了气水全耦合的水下气体射流喷射初期的流场形态及其演化过程，定性结论与实验吻合。     

水下超声速燃气射流动力学特性研究

该文研究水下超声速喷管燃气射流动力学特性.采用基于均质平衡流的mixture多相流模型和标准湍流模式,运用有限体积法和SIMPLE算法,求解了不同工况下的二维水下燃气射流的湍流流动.考虑了流体的可压缩性、黏性、重力作用、气水掺混效应和能量交换等复杂因素.通过对不同扩张比、不同水深和不同来流情况下喷管射流流场的数值计算结果的比较与分析,发现在环境背压较大的情况下,大扩张比喷管燃气射流会产生颈缩、断裂和回击现象;而小扩张比喷管和有来流情况下,喷管燃气射流形态较稳定.     

考虑横向流影响的水下齐射载荷特性研究

该文围绕多细长体水下垂直齐射载荷特性,采用VOF多相流模型、k-ε湍流模型和分层嵌套动网格等仿真技术,结合自定义函数(User-Defined Function, UDF)编程模拟的不同水深环境,并考虑艇速、筒口结构形式、筒盖和均压气体等对水下齐射过程流场状态的影响,建立了考虑横向流影响的水下齐射三维非定常多相流场仿真模型,获取了筒口流场状态、相邻位置压强载荷及海水倒灌情况等。仿真结果表明,在一定齐射间隔条件下,前发发射后筒口气泡发展及海水倒灌过程会对后发发射产生一定影响;横向流除作用于弹体产生横向载荷外,也对弹体离筒后的筒口气泡发展演变有着较大影响。该研究方法和结论可为水下齐射发射方案论证及齐射安全性分析提供相关指导。     

喷管不同摆角对水下发射导弹受力的影响

论文研究了带摆喷管推力矢量控制系统的导弹水下垂直发射时,不同喷管摆角对三维水气流场的非定常发展变化过程及对导弹受力的影响。采用燃气泡物理模型,通过水气流场的耦合计算研究燃气与水的相互作用,运用欧拉-拉格朗日和时间步进的方法跟踪燃气泡自由面。以三维欧拉方程为控制方程对喷管和燃气泡内的三维气流场进行数值计算,根据燃气泡不断运动变化的交界面生成贴体动网格,在贴体坐标系下采用无波动、无自由参数、耗散的差分格式(NND差分格式)数值求解三维气流场。采用势流理论,以拉普拉斯方程为控制方程,利用三维Hess-Smith方法数值求解了导弹与燃气泡周围的三维水流场。给出了不同时刻泡形的变化,气流场内马赫数、压力的演变规律,导弹受力及力矩。通过多个工况的对比计算,研究了喷管摆角对导弹受力及水气流场的影响。     

二期围堰防渗墙漏失层处理

三峡二期上下游围堰体水下抛填的深度达６０ｍ，其动水中平抛的砂卵石层厚，含砂量低，原河床覆盖层成分复杂，基岩风化层厚度大、块球体较多，防渗墙造孔过程中易产生漏浆。在防渗墙施工前和造孔过程中对漏失层采用预灌浓浆和投置堵料材料快速堵漏的措施，为防渗墙的正常施工创造了条件。     

利用球形气泡模型研究导弹水下点火瞬间的推力状况

本文利用由球形气泡假设所得到的简单数学模型研究了导弹在水下点火瞬间所受到的推力状况。计算结果显示由于水的惯性作用,导弹在水下点火瞬间所受到的推力将急剧增大,推力峰值随着喷管喉部截面积和膨胀面积比的增大而增大。而随着导弹发射深度的增大而减小,导弹所受到的推力在峰值后将出现低频波动。     

散粒料水下抛填堰体密度的离心模型试验研究

水利大坝施工围堰建设中,常采用水下抛填。砂、砂砾石及石碴等散粒料常被用作抛填材料,其水下抛填密度是围堰设计中的关键指标。由于散粒料水下抛填后很难直接取样测定其密度,目前也没有成熟的理论计算方法,抛填后堰体密度的确定成为困扰围堰设计和施工的难题。在分析抛填堰体密度影响因素的基础上,针对工程中应用的砂、砂砾石及石碴3种典型散粒料,设计进行了多组离心模型试验,测得了散粒料水下抛填密度,研究了颗粒形状、大小和级配等因素对水下抛填密度的影响。基于离心模型试验成果,提出了散粒体水下抛填堰体密度的估算公式,可供水下抛填围堰设计和施工参考。     

气液两相流压力波动特性

压力波动是两相流动的固有特性，研究波动规律对实现两相流动的智能监测有重要意义。本文采用统计学原理和确定性混沌学中的分形理论，对垂直上升空气水两相流的壁面静压力波动过程进行了研究，分析了表观液速对统计特征和分形特征的影响规律，首次发现环状流内高气速时压力波动的分维数大于1．5。     

Call for Papers

正As the eldest and most distributed professional journal of water industry,Water Wastewater Engineering(W WE)gained very wide acceptance from the colleagues working in this field in this country since start publication in 1964.Now it is administrated by the Ministry of Construction of the People’s Republic of China and sponsored by the China Civil Engineering Society etc.     

地下厂房施工过程的三维非线性数值模拟分析

根据冗各电站地下厂房开挖支护的施工顺序,以隐式杆单元模拟锚杆,以壳单元模拟混凝土喷层,采用三维非线性有限元技术,对洞室群的开挖支护动态过程进行了模拟计算。通过三维非线性有限元计算分析得到:洞室群动态开挖过程中围岩应力变形的分布规律,围岩塑性区的发展规律,锚杆受力变化情况。计算结果表明:整个开挖过程中,洞周围岩位移变化规律正常,量值较小,塑性区主要分布在洞室周边,围岩稳定性较好;但在洞室交叉口处围岩的变形较大,出现较大范围的塑性区,在此基础上提出了支护措施优化方案,并对优化方案的效果进行了评价。     

Serial discontinuities in a Rocky mountain river. I. Distribution and abundance of plecoptera

Samples were taken year-round at eleven sites along the altitudinal profile (2900-1400 m a.s.l.) of the Gunnison River, a 329 km tributary of the Colorado River, to document the distribution of the Plecoptera and to evaluate responses to hypolimnial-release dams in the headwaters and middle reaches. Twenty-two species were present, with the greatest species richness occurring in an unregulated segment upstream of the middle reach dams; average nymphal biomass over the study period (175 organisms, 395 mg dry mass m^?2) was also greatest in this segment. Only four species (58 organisms, 48 mg m^?2) were present in the tailwaters of the headwater dam and values were greatly reduced (nine species; 35 organisms, 180 mg m^?2) below the middle reach dams. The stonefly community recovered ca. 80 km downstream from the last dam (15 species; 244 organisms, 250 mg m^?2), apparently in response to natural resetting of environmental conditions corresponding to those above the middle reach dams. At the most downstream site (11) only four species (four organisms, 16 mg m^?2) were present. The observed distributional pattern is a classic serial discontinuity in response to hypolimnial stream regulation in a temperate latitude river.     

Impacts of Microcystis on algal biodiversity and use of new technology to remove Microcystis and dissolved nutrients

Cyanobacteria often dominate eutrophic lakes, outcompeting green algae that are required by fish and zooplankton. This study was undertaken to ascertain the impact of the cyanobacterium, Microcystis, on algal biodiversity. Under laboratory conditions, we found that the presence of Microcystis decreased phyla richness by 58%, phyla evenness by 47%, genera richness by 66% and genera evenness by 51%. Analysis by mixed anova s demonstrated a significant interaction between treatment and time and confirmed a significant reduction in richness and evenness of phyla and genera. We also conducted a phosphate restriction assay on the algae in Mason Lake (Irvine, CA, USA) and found that the threshold needed for algal growth there was 0.02 mg L^?1 PO₄. A pilot study was then conducted to test the effectiveness of the Blue Pro? water treatment facility in removal of this colonial organism from Mason Lake, in addition to removal of dissolved nutrients required for its growth. We measured a 97% reduction in Microcystis cells, a 72% reduction in chlorophyll‐a, and a 96% reduction in phosphate after just one 10 min cycle through the unit. Our study demonstrated that removal of Microcystis colonies may allow green algae to increase in numbers. This may improve algal biodiversity, which will benefit zooplankton and fishes.     

Evaluation of freshwater mussel relocation as a conservation and management strategy

The relocation of unionacean mussels is commonly used as a conservation and management tool in large rivers and streams. Relocation has been used to recolonize areas where mussel populations have been eliminated by prior pollution events, to remove mussels from construction zones and to re-establish populations of endangered species. More recently, relocation has been used to protect native freshwater mussels from colonization by the exotic zebra mussel Dreissena polymorpha. We conducted a literature review of mussel relocations and evaluated their relative success as a conservation and management strategy. We found that 43% of all relocations were conducted because of construction projects that were forced to comply with the Endangered Species Act 1973 and that only 16% were monitored for five or more consecutive years. Most (43%) relocation projects were conducted from July to September, presumably a period when reproductive stress is relatively low for most species and the metabolic rate is sufficient for reburrowing in the substrate. The mortality of relocated mussels was unreported in 27% of projects; reported mortality varied widely among projects and species and was difficult to assess. The mean mortality of relocated mussels was 49% based on an average recovery rate of 43%. There is little guidance on the methods for relocation or for monitoring the subsequent long-term status of relocated mussels. Based on this evaluation, research is needed to develop criteria for selecting a suitable relocation site and to establish appropriate methods and guidelines for conducting relocation projects.     

基于模型试验的河床砂砾石层基本特性研究

为了经济可靠地确定深厚覆盖层的基本特性参数,以大渡河双江口水电站坝基河床砂砾石层基本特性研究为工程背景,进行大尺寸模型试验,研究河床砂砾石层的旁压模量和动探击数随密度、级配以及上覆压力的变化规律。根据室内模型试验结果,结合现场旁压试验及钻孔试验成果,推断出坝址区河床砂砾石相关层位的密度,并依此进行砂砾石室内力学试验,获得设计所需力学参数。研究成果可为深厚覆盖层基本特性测试提供新的方法。     

SPATIAL AND TEMPORAL WATER QUALITY VARIABILITY IN AQUATIC HABITATS OF A CULTIVATED FLOODPLAIN

The floodplains of lowland rivers contain diverse aquatic habitats that provide valuable ecosystem services but are perturbed when intensively cultivated. Hydrologic, water chemistry and biological (fish) conditions in five aquatic habitats along the Coldwater River, Mississippi, were measured for more than 4 years: the river, two severed meanders that functioned as backwaters, a managed wetland and an ephemeral channel draining cultivated fields. Off‐channel habitats were connected to downstream regions 0.10% to 32% of the dry season and 24% to 67% of the wet season. The median temperatures for the five monitored sites ranged from 18°C to 23°C, the median total solids concentration for all sites was 135 mg L^?1, the median total phosphorus was 0.29 mg L^?1 and the median total nitrogen was 1.56 mg L^?1. Chemical and physical water quality displayed strong seasonal differences between the wet winter/spring and the dry summer/fall periods so that temporal variation consisted of gradual seasonal trends superimposed on strong diurnal variations. All off‐channel habitats exhibited periods of hypoxia and temperatures >30°C during the dry season. Between‐site gradients of water and habitat quality were strongly coupled to water depth and runoff loading. The rehabilitation of one backwater by increasing water depth and diverting agricultural runoff was associated with improved water quality and fish species richness relative to an adjacent untreated backwater. The diversion of polluted runoff and the use of water control structures to maintain greater water depth were observed to be effective management tools, but the former reduces the water supply to habitats that tend to dry up and the latter reduces connectivity. Published in 2011 by John Wiley & Sons, Ltd.     

簸箕李引黄灌区水沙分布及优化调度的经验

灌区利用水沙观测所取得的资料和试验数据，运用水沙运动力学理论，总结分析和揭示了灌区水沙分布的规律和特点。在此基础上，结合灌区的实际运行情况，围绕减少骨干渠道的淤积进行探讨、研究，进而，优化水沙调度方案。该方案实施后，骨干渠道减旅伴效果明显，取得了成功的经验。     

小湾水库大坝防渗面板及其裂缝的加固处理

小湾水库大坝防渗面板整体抗渗性能差,且存在多条裂缝,通过对面板钢丝网喷涂丙乳砂浆加固处理及其裂缝修补,大坝渗漏量明显减少,且左岸上灌浆廊道内及大坝下游坝面92～93 m高程下廊道入口处原有小股射流全部消失.     

基于BP神经网络-马尔科夫链模型的隧道围岩位移预测

在隧道工程施工中,围岩位移预测起着很重要的作用。将BP神经网络-马尔科夫链模型引入到隧道围岩位移预测中来,通过对训练样本的学习,利用BP神经网络实现了对位移时间序列的滚动预测,同时得到了实测值与预测值的相对误差;在此基础上利用马尔科夫链对相对误差进行修正,有效地提高了预测结果的精度。并将该模型应用于某公路隧道拱顶下沉位移时序预测中,结果表明该模型具有精度高、科学可靠的特点,为隧道围岩变形的预测提供了新的途径。