In this study,influence of back-wall clearance,CWL(Critical Water Level)and air content in water on flow patterns in a pump intake has been investigated experimentally and theoretically for different cases.The statist...In this study,influence of back-wall clearance,CWL(Critical Water Level)and air content in water on flow patterns in a pump intake has been investigated experimentally and theoretically for different cases.The statistical data show that CWL for a two-phase flow is lower than that in the case of a single-phase flow at a relatively low flow rate,and as the flow rate increases,this trend turns out to be completely reversed.Fine experimental data obtained under conditions of subcritical,critical and supercritical flow rates have revealed that the larger the back-wall clearance is,the more vortices exist and the higher the vorticity of free-surface vortices is.For the smallest back-wall clearance,the flow coming through the inlet occupies most space under the pipe bell,and both this flow and the inflow coming from the back wall are asymmetric relative to a certain vertical line other than the axis.For the larger and the largest back-wall clearances,the flows coming from the inlet and from the back wall are almost symmetrical relative to the vertical axis of the pipe bell.The velocity distributions on two PIV measurement lines for different back-wall clearance magnitudes indicate that the smallest back-wall clearance influences the flow around the pipe bell.展开更多
在日光温室的后墙上,采用管道无土栽培方式进行蔬菜或草莓生产,可以提高温室空间利用率和作物种植量,但可能会出现因为管道和植物的挡光而减少后墙蓄热、降低冬季温室温度的问题。为此,通过冬季连续31d的温度监测,在3种典型气象(晴天、...在日光温室的后墙上,采用管道无土栽培方式进行蔬菜或草莓生产,可以提高温室空间利用率和作物种植量,但可能会出现因为管道和植物的挡光而减少后墙蓄热、降低冬季温室温度的问题。为此,通过冬季连续31d的温度监测,在3种典型气象(晴天、阴天、雪天)条件下,对比分析了有后墙立体基质栽培的日光温室(solargreenhouse with equipment,ESG)和无后墙立体栽培的日光温室(solar greenhouse with no equipment,NSG)温度环境的变化。监测结果表明,ESG的月平均气温较NSG高0.84℃,其中最大日温差为2.22℃,最小日温差为0.14℃。晴天条件下,ESG的日平均冠层温度和1.5m高度处的空气温度分别是12.72和13.04℃,NSG分别是10.68和11.04℃;ESG的冠层温度最低值是4.68℃,而NSG最低值是4.10℃。可见,ESG较NSG的气温要略高一些;阴天和雪天条件下,2种温室内的温度环境无显著差别。因此,利用日光温室后墙进行立体基质栽培草莓,不但没有降低反而提高了冬季温室内的温度,是一种可行、值得推广应用的温室高效栽培技术。展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.51909132,52079140,51779257).
文摘In this study,influence of back-wall clearance,CWL(Critical Water Level)and air content in water on flow patterns in a pump intake has been investigated experimentally and theoretically for different cases.The statistical data show that CWL for a two-phase flow is lower than that in the case of a single-phase flow at a relatively low flow rate,and as the flow rate increases,this trend turns out to be completely reversed.Fine experimental data obtained under conditions of subcritical,critical and supercritical flow rates have revealed that the larger the back-wall clearance is,the more vortices exist and the higher the vorticity of free-surface vortices is.For the smallest back-wall clearance,the flow coming through the inlet occupies most space under the pipe bell,and both this flow and the inflow coming from the back wall are asymmetric relative to a certain vertical line other than the axis.For the larger and the largest back-wall clearances,the flows coming from the inlet and from the back wall are almost symmetrical relative to the vertical axis of the pipe bell.The velocity distributions on two PIV measurement lines for different back-wall clearance magnitudes indicate that the smallest back-wall clearance influences the flow around the pipe bell.
文摘在日光温室的后墙上,采用管道无土栽培方式进行蔬菜或草莓生产,可以提高温室空间利用率和作物种植量,但可能会出现因为管道和植物的挡光而减少后墙蓄热、降低冬季温室温度的问题。为此,通过冬季连续31d的温度监测,在3种典型气象(晴天、阴天、雪天)条件下,对比分析了有后墙立体基质栽培的日光温室(solargreenhouse with equipment,ESG)和无后墙立体栽培的日光温室(solar greenhouse with no equipment,NSG)温度环境的变化。监测结果表明,ESG的月平均气温较NSG高0.84℃,其中最大日温差为2.22℃,最小日温差为0.14℃。晴天条件下,ESG的日平均冠层温度和1.5m高度处的空气温度分别是12.72和13.04℃,NSG分别是10.68和11.04℃;ESG的冠层温度最低值是4.68℃,而NSG最低值是4.10℃。可见,ESG较NSG的气温要略高一些;阴天和雪天条件下,2种温室内的温度环境无显著差别。因此,利用日光温室后墙进行立体基质栽培草莓,不但没有降低反而提高了冬季温室内的温度,是一种可行、值得推广应用的温室高效栽培技术。
