共查询到20条相似文献,搜索用时 78 毫秒
1.
2.
本在两流体模型的基础上,使用贴体坐标的有限体积法,利用有哥氏力修正的κ-ε-Ar,两相流紊流模型建立了水轮机转轮内部的三维泥沙固液两相紊流计算模型。模型中求解了考虑压力对固粒相影响的时均Reyno1ds动量方程,并利用泥沙相的速度和浓度分布,数值计算转轮的泥沙磨损。用该模型计算了三峡水轮机转轮内部的三维泥沙固液两相紊流流动,数值预估了三个不同工况转轮的泥沙磨损情况.计算表明汛期三峡水轮机转轮将有一定的磨损,磨损的主要部位是叶片正面靠近出口和下环面的三角区。靠近山水边的磨损速率约为1.3mm/年。 相似文献
3.
4.
5.
6.
水轮机转轮三维紊流数值解析 总被引:1,自引:0,他引:1
水轮机转轮三维紊流数值解析[日本]钱逸等主题词水轮机,转轮,三维流,数字模型,计算方法近年来,随着计算机技术的迅速发展,数值计算取得了长足的进步,数值模拟在工业上的应用也发生了很大变化。最近,由于采用了数值模拟与试验相结合的方法,与只依靠实验的方法相... 相似文献
7.
8.
混流式水轮机内三维定常湍流数值研究 总被引:12,自引:0,他引:12
基于 k-ε紊流模型和三维时均N-S方程,进行了混流式水轮机全流道的三维定常湍流计算.捕捉到了水轮机过流部件内的流场和非最优工况下转轮通道及尾水管内的旋涡结构与演化特征等流动信息.结果表明,水轮机的全通道CFD分析能够较为准确地预测出水轮机过流部件内的性能参数及内部流场结构,所得到的结果对进行水轮机的水力设计或改型优化设计等研究具有重要的指导意义. 相似文献
9.
基于混合平面法的轴流式水轮机内三维湍流数值模拟 总被引:1,自引:1,他引:1
通过求解由κ-ε双方程湍流模型封闭的三维时均N-S方程对轴流式水轮机内部四个典型工况的全三维紊流场进行了计算,并采用“混合平面”法处理转轮与导叶问动静耦合流动的参数传递和相互干扰问题。捕捉到了轴流式水轮机内部压力分布和速度分布等重要的流动信息,在此基础上计算了四个工况下转轮的水力效率。结果表明,该方法能够较为准确地预测出轴流式水轮机转轮与导叶间的总性能参数及内部流场结构,所得到的结果对进行轴流式水轮机的水力设计或改型优化设计等研究具有重要的指导意义。 相似文献
10.
水沙两相浑水模型的紊流封闭及初步验证 总被引:1,自引:0,他引:1
一些学者采用两相浑水模型模拟挟沙水流运动,但其紊流封闭仍借用经验公式、单相紊流模型或双流体紊流模型,未形成两相浑水理论框架下的紊流模式。本文基于双流体紊流模型推导出固液两相浑水紊动能和紊动耗散的偏微分方程,给出固相偏移紊动能的渐近解,以表示固相紊动能与固液两相浑水紊动能的相对差,继而推导出固相紊动耗散的代数表达式,完成对固液两相浑水模型的紊流封闭。固液两相浑水紊流模型能够考虑相间作用和颗粒碰撞等物理机制,保留了双流体紊流模型能够分别计算固、液相各自紊动信息的特点,又将偏微分方程数量减少一半。采用河流动力学绝对含沙量分布的计算方法,并引入各向紊动强度分配系数进行修正后,利用实验资料对两相浑水紊流模型进行验证,计算结果同实测值符合较好,结果表明本文模型能反映出随着泥沙浓度增加,挟沙水流紊动抑制加剧的现象。 相似文献
11.
Hydrologically Based Environmental Flow Methods Applied to Rivers in the Maritime Provinces (Canada)
下载免费PDF全文
![点击此处可从《河流研究与利用》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The demand for water withdrawal continues to increase worldwide. These water withdrawals from rivers can affect fish habitat and aquatic life. As such, environmental flow assessment methods are used in order to protect rivers against excessive water withdrawals. The concept of environmental flow relates to the quantity of water required in rivers to sustain an acceptable level of living conditions for aquatic biota at various phases of their development. For many agencies, environmental flow methods are essential in environmental impact assessments and in the protection of important fisheries resources. The present study deals with the evaluation of hydrologically based environmental flow methods within the Maritime Province of Canada. In total, six hydrologically based environmental flow methods were compared using data from 52 hydrometric stations across the region. Some methods provided adequate environmental flow protection (e.g. 25% mean annual flow and Q50 flow duration method); however, other methods did not provide adequate flow protection (e.g. Q90 flow duration method and 7Q10 and 7Q2 low‐flow frequency). The 70% Q50 method provided adequate flow protection only under good baseflow conditions and should be applied with extreme caution. The present study shows the importance of the hydrologic flow regime, particularly as it pertains to the baseflow component, as a significant determinant in the level of instream flow protection. © 2014 Her Majesty the Queen in Right of Canada. River Research and Applications © 2014 John Wiley & Sons, Ltd. 相似文献
13.
AN APPROACH IN MODELING TWO-DIMENSIONAL PARTIALLY CAVITATING FLOW 总被引:10,自引:7,他引:3
1. INTRODUCTIONCavitation is a phenomenon that widely occurs in liquids. When the flow leads to the local pressure below the saturation vapor pressure of water (the fluid medium, in our research), usually incipient cavitation firstly occurs on the solid b… 相似文献
14.
The natural flow paradigm (NFP) emphasizes the need to partially or fully maintain or restore the range of natural intra‐ and interannual variation of hydrologic regimes to protect native biodiversity and the evolutionary potential of aquatic, riparian and wetland ecosystems. Based on our studies of natural and managed flow regimes in New Zealand, we do not believe that all components of the natural flow regime are necessary to achieve the objectives of the NFP, either partially or fully, because many aquatic species have very flexible niches and life‐history requirements (i.e. there is ‘ecological redundancy’). Obviously, maintaining the natural flow regime will maintain the hydrologic and hydraulic conditions necessary for sustaining natural ecosystems. However, if there is adequate knowledge of what ‘values’ need to be maintained in a waterway, and the aspects of the flow regime that are required to maintain those values are also known, then regimes can be designed that target these requirements and thus optimize conditions for the ‘values’. We believe that an assessment of ecosystem requirements using information on river processes together with habitat requirements and life‐history strategies of biota can achieve the best balance between resource use and sustaining ecosystem function and value, and show examples where changes to natural flow regimes have maintained, or even improved, instream values in some New Zealand rivers. We caution that simple flow‐based rules, such as those that might be developed under the NFP, could be unnecessarily restrictive on multiple use of water in New Zealand while, at the same time, preclude the opportunity for enhancement of key ecosystem values in many waterways. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
15.
16.
本文介绍了混合流的概念,结合某一中型水库的试验,观测了混合流在抬高尾水时的下游流态。流速分布的变化规律以及对消能效果的影响。从而说明了低水头泄洪建筑物利用挑流消能有更多的可能性。 相似文献
17.
18.
19.
Liu Fa-quan 《水动力学研究与进展(B辑)》1999,(1)
1.INTRODUCTIONInthedesignofanovertoppedrock--filldam,oneofthemajortasksistodecidethesizeofthedownstreamprotection.Theovertoppedrock--filldamismadeofporousmedia,thereforethewaterwillpenetrateintothedamfromtheupperfaceandemergeoutofitfromthelowerpart,whileitflowsoverthedam.Hence,theprotectionissubjectedtotheactionofboththeoverflowandtheseepageflow,andneitherofthemcanbenegligible.Inthiscase,theflowfieldconsistsoftwoparts:theopenflowandtheseepageflow,whichhavedifferentproperties.Infact,forthe… 相似文献
20.
本文利用计算机可视化的方法对直槽流动的数值模拟结果进行了处理,得到了若干组显示涡量场和涡管运动变化的计算机动画,通过对这些直观的动画进行分析,发现了直槽流动失稳的一些现象,对于流动稳定性的研究具有一定的参考价值。 相似文献