As a part of boundaries for a free curved surface of a Pelton bucket,the cutout is indispensable to secure the smooth entrance of the unsteady inflow of water jet into the rotating bucket.The cutout of the rotating bu...As a part of boundaries for a free curved surface of a Pelton bucket,the cutout is indispensable to secure the smooth entrance of the unsteady inflow of water jet into the rotating bucket.The cutout of the rotating bucket unsteadily separates a free jet into two branches in both space and time:the impinging branch landing on the relevant bucket surface,and the flow-off branch separated by the cutout toward the preceding bucket.In order to investigate the unsteady jet separation by the cutout three-dimensionally,a semicircular free jet was discretized into 641 nodes of boundary-fitted grids.The position P of impinging jet branch landing on the bucket surface was acquired with the relative velocity W and the water depth D at each node.The trailing edge surface of the flow-off jet branch was simultaneously computed unsteadily.The complicate unsteady interaction of the bucket cutout with the branched free jets was clarified visually with the 3D view of illustrations in order to research the unsteady hydraulic performance of Pelton turbines in space and time.展开更多
This paper will introduce experimental studies and numerical calculation on turbulent boundary layer of water flow along curved surface in our country in recent years.On the basis of the experimental studies,the effec...This paper will introduce experimental studies and numerical calculation on turbulent boundary layer of water flow along curved surface in our country in recent years.On the basis of the experimental studies,the effects of curvature and roughness on velocity distribution and pressure distribution and the change of turbulent flow boundary layer on overflow bucket concave surface is discussed.We proposed the empirical formula of velocity, pressure and the change of turbulent flow boundary layer on outlet bucket concave.According to the momentum principle,we have deduced the momentum integral equation full water depth boundary layer and using the element as control unit inside the boundary layer on concave surface of bucket.Combining with continuity equation,we have computed the boundary layer development on the bucket of a spillway.Compared with the field experimental data,the calculation results are available.Under polar coordinates,a mathematical model for simulating time-averaged flow characteristics in concave surface of bucket is established.The turbulent flow field on concave surface of bucket is calculated by SIMPLE method and this mathematical model.The flow velocity field,pressure field,distribution of turbulent kinetic energy, distribution of turbulent energy dissipating rate and distribution of shear stress are available.The calculation value is consistent with measured test data.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.50379015)the Major Science and Technology Projects in Zhejiang province(Grant No.2008C11057)
文摘As a part of boundaries for a free curved surface of a Pelton bucket,the cutout is indispensable to secure the smooth entrance of the unsteady inflow of water jet into the rotating bucket.The cutout of the rotating bucket unsteadily separates a free jet into two branches in both space and time:the impinging branch landing on the relevant bucket surface,and the flow-off branch separated by the cutout toward the preceding bucket.In order to investigate the unsteady jet separation by the cutout three-dimensionally,a semicircular free jet was discretized into 641 nodes of boundary-fitted grids.The position P of impinging jet branch landing on the bucket surface was acquired with the relative velocity W and the water depth D at each node.The trailing edge surface of the flow-off jet branch was simultaneously computed unsteadily.The complicate unsteady interaction of the bucket cutout with the branched free jets was clarified visually with the 3D view of illustrations in order to research the unsteady hydraulic performance of Pelton turbines in space and time.
文摘This paper will introduce experimental studies and numerical calculation on turbulent boundary layer of water flow along curved surface in our country in recent years.On the basis of the experimental studies,the effects of curvature and roughness on velocity distribution and pressure distribution and the change of turbulent flow boundary layer on overflow bucket concave surface is discussed.We proposed the empirical formula of velocity, pressure and the change of turbulent flow boundary layer on outlet bucket concave.According to the momentum principle,we have deduced the momentum integral equation full water depth boundary layer and using the element as control unit inside the boundary layer on concave surface of bucket.Combining with continuity equation,we have computed the boundary layer development on the bucket of a spillway.Compared with the field experimental data,the calculation results are available.Under polar coordinates,a mathematical model for simulating time-averaged flow characteristics in concave surface of bucket is established.The turbulent flow field on concave surface of bucket is calculated by SIMPLE method and this mathematical model.The flow velocity field,pressure field,distribution of turbulent kinetic energy, distribution of turbulent energy dissipating rate and distribution of shear stress are available.The calculation value is consistent with measured test data.
