基于VOF(Volume of Fluid)方法和有限体积法求解气、水两相流动的RANS方程,并结合动网格技术,对物体垂直入水空泡流动进行了数值计算研究。通过对球体垂直入水早期空泡形态进行数值计算,并将计算结果与May A理想空泡模型拟合结果进行对...基于VOF(Volume of Fluid)方法和有限体积法求解气、水两相流动的RANS方程,并结合动网格技术,对物体垂直入水空泡流动进行了数值计算研究。通过对球体垂直入水早期空泡形态进行数值计算,并将计算结果与May A理想空泡模型拟合结果进行对比分析,二者具有较好的一致性,验证了数值计算方法的有效性。在此基础之上,进一步研究了150°锥角回转体垂直入水空泡生成过程,空泡壁面运动特性和空泡表面闭合特性,给出了垂直匀速入水空泡形态随时间变化规律,空泡壁面随入水过程时间变化运动规律,以及空泡表面闭合时间与入水速度之间的关系。展开更多
It is proved that air entrainment is one of the efficient measures dealing with cavi-tation control for the release works of hydropower projects. There are many factors to be considered in designing a chute aerator. O...It is proved that air entrainment is one of the efficient measures dealing with cavi-tation control for the release works of hydropower projects. There are many factors to be considered in designing a chute aerator. One of the most important factors concerns the cavity length below the aerator,which has outstanding effects on air entrainment against cavitation damage. It is crucial to determine reasonable emergence angle for the calculation of the cavity length. In the present paper the overall effects of structural and hydraulic parameters on the emergence angle of the flow from the aerator were analyzed. Four improved expressions of the emer-gence angle with weight coefficient were investigated through experimental data of 68 points observed from 12 aerators of 6 hydropower projects,of both model and prototype,on the basis of error theory. A method to calculate the cavity length be-low aerators was suggested,which considers overall effects of the above men-tioned parameters. Comparison between the method in this paper and the other five methods of calculating the cavity length showed that the present method is much more reliable than the existing methods while the mean error of the method is less than others.展开更多
This research is intended to provide academic reference and design guidance for further studies to determine the most effective means to reduce a ship’s resistance through an air-cavity. On the basis of potential the...This research is intended to provide academic reference and design guidance for further studies to determine the most effective means to reduce a ship’s resistance through an air-cavity. On the basis of potential theory and on the assumption of an ideal and irrotational fluid, this paper drives a method for calculating air cavity formation using slender ship theory then points out the parameters directly related to the formation of air cavities and their interrelationships. Simulations showed that the formation of an air cavity is affected by cavitation number, velocity, groove geometry and groove size. When the ship’s velocity and groove structure are given, the cavitation number must be within range to form a steady air cavity. The interface between air and water forms a wave shape and could be adjusted by an air injection system.展开更多
It is well known that the effect of air entrainment for cavitation damage controls is related not only to the air discharge into aerator devices but also the flow regime of the cavity below them.On the basis of the hy...It is well known that the effect of air entrainment for cavitation damage controls is related not only to the air discharge into aerator devices but also the flow regime of the cavity below them.On the basis of the hydraulic characteristics of the flow,the aerator devices were for the first time classified.The theoretical considerations were performed about the jet length and cavity flow regime with the influencing factors.Comparing with the behavior of the flow through the aerator of discharge tunnels,the flow regimes of the cavity below spillway aerators were experimentally investigated,and the empirical expressions were presented to identify the conversions of the cavity flow regimes,including fully filled cavity,partially filled cavity,and net air cavity.Some issues of the design of the aerator devices were suggested in the present work.展开更多
文摘基于VOF(Volume of Fluid)方法和有限体积法求解气、水两相流动的RANS方程,并结合动网格技术,对物体垂直入水空泡流动进行了数值计算研究。通过对球体垂直入水早期空泡形态进行数值计算,并将计算结果与May A理想空泡模型拟合结果进行对比分析,二者具有较好的一致性,验证了数值计算方法的有效性。在此基础之上,进一步研究了150°锥角回转体垂直入水空泡生成过程,空泡壁面运动特性和空泡表面闭合特性,给出了垂直匀速入水空泡形态随时间变化规律,空泡壁面随入水过程时间变化运动规律,以及空泡表面闭合时间与入水速度之间的关系。
基金the National Natural Science Foundation of China (Grant No. 50539060)the Innovative Project of Graduate Student in Jiangsu Province (Grant No. 2005-60)
文摘It is proved that air entrainment is one of the efficient measures dealing with cavi-tation control for the release works of hydropower projects. There are many factors to be considered in designing a chute aerator. One of the most important factors concerns the cavity length below the aerator,which has outstanding effects on air entrainment against cavitation damage. It is crucial to determine reasonable emergence angle for the calculation of the cavity length. In the present paper the overall effects of structural and hydraulic parameters on the emergence angle of the flow from the aerator were analyzed. Four improved expressions of the emer-gence angle with weight coefficient were investigated through experimental data of 68 points observed from 12 aerators of 6 hydropower projects,of both model and prototype,on the basis of error theory. A method to calculate the cavity length be-low aerators was suggested,which considers overall effects of the above men-tioned parameters. Comparison between the method in this paper and the other five methods of calculating the cavity length showed that the present method is much more reliable than the existing methods while the mean error of the method is less than others.
基金the Sustention of the Ministry of Education for Excellent Homecoming Researchers.
文摘This research is intended to provide academic reference and design guidance for further studies to determine the most effective means to reduce a ship’s resistance through an air-cavity. On the basis of potential theory and on the assumption of an ideal and irrotational fluid, this paper drives a method for calculating air cavity formation using slender ship theory then points out the parameters directly related to the formation of air cavities and their interrelationships. Simulations showed that the formation of an air cavity is affected by cavitation number, velocity, groove geometry and groove size. When the ship’s velocity and groove structure are given, the cavitation number must be within range to form a steady air cavity. The interface between air and water forms a wave shape and could be adjusted by an air injection system.
基金supported by the National Natural Science Foundation of China (Grant No. 51179114)the Innovative Project of Graduate Student in Jiangsu Province (Grant No. CXLX11_0443)
文摘It is well known that the effect of air entrainment for cavitation damage controls is related not only to the air discharge into aerator devices but also the flow regime of the cavity below them.On the basis of the hydraulic characteristics of the flow,the aerator devices were for the first time classified.The theoretical considerations were performed about the jet length and cavity flow regime with the influencing factors.Comparing with the behavior of the flow through the aerator of discharge tunnels,the flow regimes of the cavity below spillway aerators were experimentally investigated,and the empirical expressions were presented to identify the conversions of the cavity flow regimes,including fully filled cavity,partially filled cavity,and net air cavity.Some issues of the design of the aerator devices were suggested in the present work.
