Local scour downstream of sluice gates in erosive beds is one of the main concerns of hydraulic engineers because it can cause considerable damage to structures.Many researchers have conducted various studies to predi...Local scour downstream of sluice gates in erosive beds is one of the main concerns of hydraulic engineers because it can cause considerable damage to structures.Many researchers have conducted various studies to predict the maximum depth and length of scour holes and to develop new methods to control this phenomenon.In the methods that have recently been examined,embedded buried plates are used to control the scour in the erosive beds.In this study,using a physical model,the effect of buried plates in erosive beds on the depth of scour downstream of a hydraulic jump was studied.Several experiments were performed in which plates were buried at 50° and 90° angles at different distances from the apron in open channels with horizontal and reverse bed slopes.The results of experiments in which the scour profiles were drawn in dimensionless forms show that the angle and position of the plates are important to controlling and reducing scour depth.In fact,by reducing the angle of buried plates,the maximum depth of scour is also reduced.Also,comparison of the results of a single buried plate and double buried plates shows that using two buried plates at the distances of 30 and 45 cm from the non-erodible bed is more effective in reducing the scour depth.The best distances of the buried plates with angles of 90° and 50° from the non-erodible bed are 45 cm and 30 cm,respectively,in the condition with a single buried plate.展开更多
According to the principle of grain refining and slurry preparation by cooling sloping plate process, the distributions of boundary layers during melt treatment by cooling sloping plate were studied, and mathematic mo...According to the principle of grain refining and slurry preparation by cooling sloping plate process, the distributions of boundary layers during melt treatment by cooling sloping plate were studied, and mathematic model of cooling rate was established. The calculation value approximately agrees with the experimental result. Laminar flow and turbulent flow exist on sloping plate surface commonly. The thickness of velocity boundary layer and the critical transfer distance from laminar flow to turbulent flow increase with the decrease of initial flow velocity. The thickness of temperature boundary layer increases with the increment of flow distance and the decrease of initial flow velocity. The melt cooling rate and melt thickness have an inverse proportion relationship. The melt cooling rate increases along the plate direction gradually when the initial flow velocity is lower than 1 m/s, the melt cooling rate keeps nearly a constant when the initial flow velocity is 1 m/ s, when the initial flow velocity is higher than 1 m/s, the melt cooling rate decreases gradually. The melt cooling rate of cooling sloping plate process can reach 102-103 K/s and belongs to meta-rapid solidification scope.展开更多
Semisolid metal forming by a novel sloping plate process was studied. A sloping plate with wavelike surface was used to prepare semisolid alloy. Semisolid billets and slurries with good microstructures and excellent p...Semisolid metal forming by a novel sloping plate process was studied. A sloping plate with wavelike surface was used to prepare semisolid alloy. Semisolid billets and slurries with good microstructures and excellent property were prepared by cooling or preheating the sloping plate. During preparing semisolid alloy by the proposed process, the co-action of burst nucleation and dendrite fragmentation causes fine spherical microstructure formation, and casting temperature, cooling strength and sloping angle are the main factors influencing the alloy microstructure. Under the current experimental conditions, in order to prepare good quality semisolid billets, proper casting temperature ranges of 660-690℃for AlMg3 alloy and 660-680℃for AlSi6Mg2 alloy are suggested. A small car hub wheel of AlSi6Mg2 alloy was thixoformed, and its pattern and inner microstructure are fine. The reasonable technological conditions for preparing AlSi6Mg2 slurry are also proposed: the sloping plate preheating temperature is 300℃, and the casting temperature is 680℃.展开更多
The irregular wave experiment on the stability of the Grate Plate was carried out in the light of the wind wave spectrum recently advanced by Prof. Wen Shengchang. The stability formulas of GP under the action of irre...The irregular wave experiment on the stability of the Grate Plate was carried out in the light of the wind wave spectrum recently advanced by Prof. Wen Shengchang. The stability formulas of GP under the action of irregular waves were procured. Comparisons between the formulas obtained and those of GP under regular waves advanced by the first author in 1993 showed a coincident result.展开更多
文摘Local scour downstream of sluice gates in erosive beds is one of the main concerns of hydraulic engineers because it can cause considerable damage to structures.Many researchers have conducted various studies to predict the maximum depth and length of scour holes and to develop new methods to control this phenomenon.In the methods that have recently been examined,embedded buried plates are used to control the scour in the erosive beds.In this study,using a physical model,the effect of buried plates in erosive beds on the depth of scour downstream of a hydraulic jump was studied.Several experiments were performed in which plates were buried at 50° and 90° angles at different distances from the apron in open channels with horizontal and reverse bed slopes.The results of experiments in which the scour profiles were drawn in dimensionless forms show that the angle and position of the plates are important to controlling and reducing scour depth.In fact,by reducing the angle of buried plates,the maximum depth of scour is also reduced.Also,comparison of the results of a single buried plate and double buried plates shows that using two buried plates at the distances of 30 and 45 cm from the non-erodible bed is more effective in reducing the scour depth.The best distances of the buried plates with angles of 90° and 50° from the non-erodible bed are 45 cm and 30 cm,respectively,in the condition with a single buried plate.
基金Funded by the National Natural Science Foundation for Outstanding Young Scholars of China(No.51222405)the National Natural Science Foundation of China(No.51034002)+2 种基金the Fok Ying Tong Education Foundation(No.132002)the Basic Scientific Research Operation of Center University(N120602002,N120502001)the Chinese National Programfor Fundamental Research and Development(No.2011CB610405)
文摘According to the principle of grain refining and slurry preparation by cooling sloping plate process, the distributions of boundary layers during melt treatment by cooling sloping plate were studied, and mathematic model of cooling rate was established. The calculation value approximately agrees with the experimental result. Laminar flow and turbulent flow exist on sloping plate surface commonly. The thickness of velocity boundary layer and the critical transfer distance from laminar flow to turbulent flow increase with the decrease of initial flow velocity. The thickness of temperature boundary layer increases with the increment of flow distance and the decrease of initial flow velocity. The melt cooling rate and melt thickness have an inverse proportion relationship. The melt cooling rate increases along the plate direction gradually when the initial flow velocity is lower than 1 m/s, the melt cooling rate keeps nearly a constant when the initial flow velocity is 1 m/ s, when the initial flow velocity is higher than 1 m/s, the melt cooling rate decreases gradually. The melt cooling rate of cooling sloping plate process can reach 102-103 K/s and belongs to meta-rapid solidification scope.
基金Project(50604007) supported by the National Natural Science Foundation of ChinaProject(20041006) supported by Returnee Foundation of Educational Ministry and Natrual Science Foundation of Liaoning Province, China
文摘Semisolid metal forming by a novel sloping plate process was studied. A sloping plate with wavelike surface was used to prepare semisolid alloy. Semisolid billets and slurries with good microstructures and excellent property were prepared by cooling or preheating the sloping plate. During preparing semisolid alloy by the proposed process, the co-action of burst nucleation and dendrite fragmentation causes fine spherical microstructure formation, and casting temperature, cooling strength and sloping angle are the main factors influencing the alloy microstructure. Under the current experimental conditions, in order to prepare good quality semisolid billets, proper casting temperature ranges of 660-690℃for AlMg3 alloy and 660-680℃for AlSi6Mg2 alloy are suggested. A small car hub wheel of AlSi6Mg2 alloy was thixoformed, and its pattern and inner microstructure are fine. The reasonable technological conditions for preparing AlSi6Mg2 slurry are also proposed: the sloping plate preheating temperature is 300℃, and the casting temperature is 680℃.
文摘The irregular wave experiment on the stability of the Grate Plate was carried out in the light of the wind wave spectrum recently advanced by Prof. Wen Shengchang. The stability formulas of GP under the action of irregular waves were procured. Comparisons between the formulas obtained and those of GP under regular waves advanced by the first author in 1993 showed a coincident result.
