An experimental study to investigate various features of subsurface vortices and their evolutions inside a closed pump intake under different pressure conditions at free surface,and to analyze the influence of a pipe ...An experimental study to investigate various features of subsurface vortices and their evolutions inside a closed pump intake under different pressure conditions at free surface,and to analyze the influence of a pipe bell with different mean axial velocities at the same water level on flow patterns is presented.For all cases,three different flow regimes are closely observed:various side-wall attached,back-wall attached and submerged vortices structures,and their evolutions are subject to the free-surface pressure for a critical flow rate,the number and strength of all these vortex rise as the absolute value of the pressure increases for a higher flow rate,for a lower flow rate,whether the side-wall vortices occur or not is related closely to the pressure magnitude,and there are no vortices for lower absolute pressure values,the number and the strength of the side-wall vortices increase as the absolute pressure values increase.Besides,based on statistical analyses,the side-wall vortex probability on the right side along the stream-wise direction is much higher than that on the opposite side for all operation cases,particularly single vortex probability,and the back-wall vortex probabilities are quite higher with values of more than 90%,meanwhile,the multi-vortices probability is much higher than that of the single-vortex.The captured vortices have been qualitatively classified into different“vortex zones”:no vortex zones and vortex zones including transition,single-and multi-vortex.The Reynolds number and the absolute value pressure are the most important parameters which influence the existence and the number of these vortices,and the increase of the two parameters reduces the no vortex transition zone and causes bigger difference in the back-wall and side-wall vortex zones.展开更多
INTRODUCTION The recent trend toward more extreme periods of drought has been a shock to the residents of the Pacific Northwest-many of whom have relied upon heavy water-use in the summer months in order to make a liv...INTRODUCTION The recent trend toward more extreme periods of drought has been a shock to the residents of the Pacific Northwest-many of whom have relied upon heavy water-use in the summer months in order to make a living(i.e.producers of grass seed and sod,berries,or nursery crops),or to maintain their landscapes at high levels(i.e.certain homeowners,recreational facilities,or commercial properties).Further-more,population growth has reached the point where even an average year of pre-cipitation has proven insufficient for urbanities that had not previously experienced issues with water scarcity(McDonald et al.,2011).This modern climate scenario has forced people of the Pacific Northwest,and people from all around the world,to rethink their water-use strategies,as the global trend has shifted toward greater sustainability(Tilman,2001;McDonald et al.,2011).展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.51479196,51779257)the National Natural Science Foundation for the Youth of China(Grant No.51909132).
文摘An experimental study to investigate various features of subsurface vortices and their evolutions inside a closed pump intake under different pressure conditions at free surface,and to analyze the influence of a pipe bell with different mean axial velocities at the same water level on flow patterns is presented.For all cases,three different flow regimes are closely observed:various side-wall attached,back-wall attached and submerged vortices structures,and their evolutions are subject to the free-surface pressure for a critical flow rate,the number and strength of all these vortex rise as the absolute value of the pressure increases for a higher flow rate,for a lower flow rate,whether the side-wall vortices occur or not is related closely to the pressure magnitude,and there are no vortices for lower absolute pressure values,the number and the strength of the side-wall vortices increase as the absolute pressure values increase.Besides,based on statistical analyses,the side-wall vortex probability on the right side along the stream-wise direction is much higher than that on the opposite side for all operation cases,particularly single vortex probability,and the back-wall vortex probabilities are quite higher with values of more than 90%,meanwhile,the multi-vortices probability is much higher than that of the single-vortex.The captured vortices have been qualitatively classified into different“vortex zones”:no vortex zones and vortex zones including transition,single-and multi-vortex.The Reynolds number and the absolute value pressure are the most important parameters which influence the existence and the number of these vortices,and the increase of the two parameters reduces the no vortex transition zone and causes bigger difference in the back-wall and side-wall vortex zones.
文摘INTRODUCTION The recent trend toward more extreme periods of drought has been a shock to the residents of the Pacific Northwest-many of whom have relied upon heavy water-use in the summer months in order to make a living(i.e.producers of grass seed and sod,berries,or nursery crops),or to maintain their landscapes at high levels(i.e.certain homeowners,recreational facilities,or commercial properties).Further-more,population growth has reached the point where even an average year of pre-cipitation has proven insufficient for urbanities that had not previously experienced issues with water scarcity(McDonald et al.,2011).This modern climate scenario has forced people of the Pacific Northwest,and people from all around the world,to rethink their water-use strategies,as the global trend has shifted toward greater sustainability(Tilman,2001;McDonald et al.,2011).
