共查询到20条相似文献,搜索用时 203 毫秒
1.
2.
三维水流河床变形数学模型 总被引:4,自引:3,他引:1
本文针对三维水流所具有的紊动各向异性,不规则边界及自由表面和动床问题。采用修正的K-ε模型封闭Reynolds方程作为紊流控制方程;引入通度概念处理不规则边界;引用VOF法追踪自由表面;根据冲刷过程的物理特性推得冲刷坑的发展规律并用前人公式及试验资料验证。最后,作为例子就南水北调中线方案名河渡槽河段的流场和河床变形进行数值模拟,给出了一些工程上有用的结果。 相似文献
3.
一种新的三维孔口水流数值解法 总被引:3,自引:0,他引:3
本文提出了一种新的三维孔口水流数值解法,在势流假设下,通过调和变换,将具有复杂边界形状的物理空间(x,y,z),转换到规则空间(ξ,η,β)上,用显式迭代方法解出势函数,进而可求出三维流场的流速分布、压力分布、自由表面位置和泄流量.这种解法不但解决了三维求解中遇到的网格结点布置的困难,而且占用计算机内存少,可在微机上实现.算例表明,该算法有很好的收敛性,计算结果与试验值较好地吻合. 相似文献
4.
三维过坝水流是一种具有自由表面的临界流动,即使在势流假设下,因其非线性强,数值求解时也会遇到较大困难,目前尚未见到有效势流解法。本文提出一种正交调和变换法,可方便地采用笔者曾提出的自由表面位移理论,同步解出待定的自由表面位置和未知能头(或流量)。算例表明,该三维过坝水流的计算方法是成功的,计算结果与试验值吻合较好。 相似文献
5.
《黑龙江水利科技》2019,(11)
文章综合漂移通量模型、卷气模型和紊流模型,三维数值模拟了某实际导流工程下泄水流局部掺气的影响。针对复杂地形条件的导流工程采用CATIA软件建立三维几何模型。然后对溢洪道水流局部掺气条件下的导流工程整体流场利用Tru VOF水流自由表面追踪法、卷气模块及RNG k-ε紊流模型进行了计算,从而揭示了水力参数压强、水位和流态的分布规律,通过对比分析数值模拟结果和物理模型试验验证了模型的可靠性。研究表明:数值模拟能够较为准确的计算上游围堰设计高程,在导流工程流场计算中具有较强的科学性和有效性;在三维流场中引入卷气模块较好的揭示了掺气范围、水流掺气浓度、压强及流速分布特征,可为其他类似工程的计算模拟提供一定参考价值。 相似文献
6.
带有自由表面紊流流场的数值模拟 总被引:3,自引:0,他引:3
带有自由表面的三维强紊动水流在水利水电工程中,以及其他一些领域普遍存在.对该种紊流的数值模拟历来是一个十分具有挑战的领域.应用双流体模型与传统的标准κ—ε双方程紊流模型相耦合,对水垫塘中紊流流场进行了数值模拟、数值计算结果与物模测量结果具有较好的一致性。 相似文献
7.
宽顶堰水流数值模拟分析 总被引:1,自引:0,他引:1
本文利用紊流模型模拟了带有曲线自由表面的宽顶堰流的紊流流场,采用VOF法来确定自由表面,采用气液两相流计算模型对宽顶堰流场进行了数值模拟,计算结果与试验数据较为吻合.模拟结果表明,数值模拟是作为研究水利工程中带有自由表面的水流结构的一个强有力的工具,其结果对物理试验也是一个很好的补充. 相似文献
8.
9.
该文采用具有自由水面和河床切应力计算的三维数学模型分析了桥墩群对河道水流的影响。计算利用标准的k-ε紊流模型求解N-S方程得到三维流场,通过对运动方程的垂向平均积分得到求解水位的泊松方程,将该模型应用到不同收缩比条件下桥墩的绕流壅水计算,结果与物理试验值拟合较好。在实际应用中,模型比较了凉水河北京南站段桥墩群修建前后河道水位和三维流场的变化情况,分析了桥墩群对河道三维水流与水位的影响,为该段河道的整治以及规划设计提供参考。 相似文献
10.
11.
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。 相似文献
12.
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. 相似文献
13.
14.
15.
In the lower River Murray, Australia, populations of gastropods have declined markedly over the past 40 years. Of the native fauna of about 18 species, only the ancylid Ferrissia petterdi remains common (but in patches), and another five species feature in sporadic local resurgences. Until recently the viviparid Notopala was thought to be extinct. The introduced physid Physa acuta is widespread, but in low numbers. The decline probably is associated with flow regulation, high turbidity and the introduction of common carp. Snail populations have persisted, however, in irrigation pipelines fed from the river, where they periodically cause blockages. This paper reports the discovery of the only known populaion of Notopala hanleyi in a pipeline where the inner wall accumulates microbial and other organic matter, providing high quality food for snails. In the Murray before regulation most of the periphytic biomass was probably microbial, as fluctuating water levels would have maintained littoral communities in a highly productive, early state of succession his postulated that, by stabilizing seasonal water levels, regulation has promoted the production of filamentous green algae, an inferior food source, and so displaced snail populations from the open aquatic environment. 相似文献
16.
17.
18.
简述天湖水电站投运以来各种故障的表现形式,分析其原因,提出了相应的处理方法及措施,并对合理利用国内外设备提出建议。 相似文献
19.
Various designs of low‐head dams are used to rehabilitate streams or forestall upstream channel incision after channelization. We report on the efficacy of using notched sills and grade control structures (GCS) to restore the fish assemblage in Luxapallila Creek, Mississippi. We tested the null hypotheses that habitat variables and species richness, evenness, and assemblage structure would not differ among: (1) a channelized segment with no modifications; (2) a channelized segment mitigated by the installation of sills and GCS; (3) a segment upstream of the installations and undergoing channel incision; and (4) an unaltered segment. Although habitat variables changed, neither species richness, evenness, nor fish assemblage structure differed between mitigated and channelized segments with both exhibiting less richness and different assemblage structures than the unaltered segment. Lack of differences in species richness between the incised and unaltered segments suggest that the GCS may have halted the negative effects of upstream channel incision before species were extirpated. Conspicuous habitat differences between the altered (channelized and mitigated) and unaltered segments were lack of backwaters and canopy coverage and finer substrates in the altered segments. Our results suggest a more comprehensive rehabilitation strategy is required in Luxapallila Creek. Published in 2003 by John Wiley & Sons, Ltd. 相似文献
20.
NUMERICAL STUDY OF WAVE EFFECTS ON SURFACE WIND STRESS AND SURFACE MIXING LENGTH BY THREE-DIMENSIONAL CIRCULATION MODELING 总被引:1,自引:0,他引:1
LIANG Bing-chen LI Hua-jun LEE Dong-yong 《水动力学研究与进展(B辑)》2006,18(4):397-404
1. INTRODUCTION Coastal and continental shelf regions are characterized by intensive interaction between wave and current. These regions are of great economic significance to mankind. Therefore, the modeling of wave and current as well as their mutual int… 相似文献