共查询到19条相似文献,搜索用时 187 毫秒
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针对中华鲟栖息地保护的问题,在已有的中华鲟产卵场产卵季节各生态因子实测资料的基础上,运用因子分析法对中华鲟栖息地生态影响因子进行了分析,从中提取了影响中华鲟栖息地的3个主因子。结果表明,第一个主因子F1主要由平均流速、含沙量及底质贡献,其为影响中华鲟卵孵化的条件;第二个主因子F2主要由平均水深和平均流速贡献,其为影响中华鲟产卵的条件;第三个主因子F3主要由平均水温和食卵鱼数贡献,其为影响中华鲟卵存活的条件。 相似文献
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为探究梯级枢纽建设及运行对信江下游四大家鱼产卵场水文情势的潜在影响,选取21项参数建立鱼类产卵场水文评价指标体系,采用一维水动力模型分析了大溪渡产卵场河段在梯级枢纽建设前后的水文情势,并采用变动范围法分析了梯级枢纽建设前后产卵场繁殖期生态水文变化情况。结果表明,四大家鱼繁殖期流量在枢纽运行后呈下降趋势,研究区域断面流量趋于平均;高流量脉冲数量减少,降低了脉冲流量对四大家鱼产卵的刺激性信号。研究量化了信江下游梯级枢纽建设对库区内产卵场繁殖期生态水文的影响,为当地枢纽调度运行的方案设计提供科学指导。 相似文献
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四川省机械工程学会动力委员会于4月25日~28日,在葛洲坝工程现场举行了“葛洲坝工程现场及大型水电机组安装考察”活动,有省内15个单位、30名代表参加。 葛洲坝水利枢纽工程,主要由拦河坝,发电站、船闸、泄水闸、冲砂闸和鱼道等建筑物组成。大坝全长2561米、总库容为15.8亿米~3。电站装机21台,总容量为271.5万千瓦,采用低水头径流发电,平均年发电量为138亿度。 相似文献
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A novel flow field for algae raceways has been proposed, which is fundamentally different from traditional paddlewheel-driven raceways. To reduce freezing and heat loss in the raceway during cold time, the water is drained to a deep storage canal. The ground bed of the new raceway has a low slope so that water, lifted by propeller pump, can flow down in laterally-laid serpentine channels, relying on gravitational force. The flow rate of water is controlled so that it can overflow the lateral channel walls and mix with the main flow in the next lower channel, which thus creates a better mixing. In order to optimize the design parameters of the new flow field, methods including flow visualization, local point velocity measurement, and CFD analysis were employed to investigate the flow mixing features. Different combinations of channel geometries and water velocities were evaluated. An optimized flow field design and details of flow mixing are presented. The study offers an innovative design for large scale algae growth raceways which is of significance to the algae and biofuel industry. 相似文献
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Studied is a three-dimensional simulator of single-phase, hot-water flow which consists of fracture-type flow and recharge from the ground surface. Equations as applied to the simulator, and some assumptions and methods of solution are also described. These are applied to modeling of a geothermal field where exploration on geothermal activity is being conducted at present. As a result, it has been possible to infer some phenomena which appear to be related to hot-water flow in the earth's crust. 相似文献
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The issue of natural and forced groundwater movements, and its effect on the performance of ground heat exchangers is of great importance for the design and sizing of borehole thermal energy systems (BTESs). In Scandinavia groundwater filled boreholes in hard rock are commonly used. In such boreholes one or more intersecting fractures provide a path for groundwater flow between the borehole and the surrounding rock. An enhanced heat transport then occurs due to the induced convective water flow, driven by the volumetric expansion of heated water. Warm groundwater leaves through fractures in the upper part of the borehole while groundwater of ambient temperature enters the borehole through fractures at larger depths. This temperature driven flow is referred to as thermosiphon, and may cause considerable increase in the heat transport from groundwater filled boreholes. The thermosiphon effect is connected to thermal response tests, where the effective ground thermal conductivity is enhanced by this convective transport. Strong thermosiphon effects have frequently been observed in field measurements. The character of this effect is similar to that of artesian flow through boreholes. 相似文献
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以某火电厂锅炉尾部烟道为研究对象,运用CFD仿真计算技术,对锅炉尾部烟道进行建模计算,分析了改进前后烟道流场及阻力分布。结果表明:该电厂原有烟道A、B侧增压风机出口至二级烟冷器前烟气流动阻力为944 Pa,现场试验测试该段烟道阻力为890 Pa,相对误差为6%,模拟计算压力数据与现场试验测量压力数据结果基本吻合,且该段烟道内流场分布不均匀,烟气流动过程中存在很多涡流区域。提出四种改进方案:方案一取消上升段烟道,将烟道置于地面;方案二在方案一的基础上,在两侧烟气汇合处及弯头处增加导流板;方案三由烟气中间汇合改为单边汇合;方案四采用圆形烟道。四种改进方案可分别将该段烟道阻力降至500、400、317和105 Pa。方案三及方案四对于烟气阻力降低的效果较明显,但方案四烟气流速均匀性分布效果较差。综合阻力及速度分布情况来看,改进方案三更加合适。 相似文献