【作者】 邹鹏飞；

【导师】 王均星；

【作者基本信息】 武汉大学 ， 水工结构工程， 2004， 硕士

【摘要】 挑流消能是水电工程中重要的消能方式之一。挑射水流对岩石河床的冲刷问题，从宏观上看主要是入射水流的冲击能力和河床基岩的抗冲能力两者相互作用的结果。本文从以上两个方面着手，主要对挑流消能冲坑内的水流脉动特性和冲刷机理进行了研究。 针对入射水流的冲击能力，引用斜向淹没冲击射流的研究成果，分析了淹没射流的扩散规律，壁面压强的特征和脉动压强的成因；通过冲坑底部脉动压强的试验研究，运用数理统计和频谱分析方法论述了淹没射流冲坑底部的脉动压强及其分布特性，概化出冲坑内脉动压强载荷的波动表达方式。 针对岩石河床的抗冲能力，探讨了考虑阻力的岩块起动的判别条件。采用Ansys有限元软件的模态分析模块分析了冲坑岩块的振动特性。引入瞬变流模型，探讨了岩缝内脉动压力波的传播规律和脉动上举力的成因，推导了可能最大脉动上举力的计算公式和考虑阻力的岩块振动位移与脉动上举力之间的统计关系式。运用岩块起动的动力方程进行了瞬态动力分析，得到了冲坑岩体在脉动水压力作用时的动应力分布规律，推求出考虑阻力的平衡冲刷深度的预报公式。 本文所取得的研究成果可为水工设计和研究冲刷问题提供参考。更多还原

【Abstract】 Energy dissipation of ski-jump type is very important in the hydroelectric power engineering. In the macroscopic view, the scouring by jet fluids on the rocky river beds results from the combined action of the impulsive forces of the incident fluids and the scour resistances of the river bedrocks. According to above two sides, the characteristics of pressure fluctuations in the scour pit and the mechanism of scouring by jet fluids are researched in this thesis.As far as the impulsive forces of the incident fluids are concerned, based on the mainly researching results of the oblique-submerged turbulent impinging jet, the diflusive characteristics for a submerged turbulent impinging jet, the pressure features at the bottom of the scour pit and the cause of generating fluctuating pressures are analysed. According to the model experiments, fluctuating pressures and their distribution at the bottom of the scour pit by submerged turbulent impinging jet are discussed by use of the methods of mathematical statistice and spectrum analysis. The wave equation of the fluctuating pressures at the bottom of the scour pit is generalized.As far as the scour resistances on the rocky river beds are concerned, the lifting conditions considered resisting forces for rock blocks in the scour pit are investigated. The vibration naturals for rock blocks are obtained through modal analytical module of finite element software-Ansys. By leading-in the model for transient flow, the mechanism of fluctuating pressure transmission in cracks of the bed rock and the cause of generating fluctuating uplift are discussed. A predicting formula for the maximum fluctuating uplift on rock blocks in a scour pool is deduced. A statistical relational expression considered resistance forces about vibration displacement and fluctuating uplift forces of rock blocks is put forward. The regularities of distribution about dynamic stress by fluctuating pressures of the rock masses at the bottom of the scour pit are gained through transient dynamic analysis. The predicting formula considered resistance forces for the limiting scour depth is obtained.These results in this thesis have reference value for the hydraulic design and the scouring.更多还原