长陡坡无压隧洞洞内阶梯消能试验研究

【作者】 杨红宣；

【导师】 王海军；

【作者基本信息】 昆明理工大学 ， 水利水电工程， 2012， 硕士

【摘要】 为探求适合长陡坡无压隧洞的内流消能措施,提出了隧洞长陡坡段采用沿程消能的阶梯消能形式,为进一步研究阶梯溢流消能效果,采用物理模型试验与理论分析相结合的方法,对陡坡段阶梯消能的水流特性、消能效果和陡坡段后底流消能工设置的必要性进行了研究。通过对不同台阶尺寸、不同单宽流量下陡坡段阶梯溢流面上水流流态的观测和分析,提出阶梯消能的关键在于合理选用台阶形式和尺寸,以力求在较长的流程上形成滑掠水流流态,合适的台阶尺寸和阶梯布置形式能够适应下泄较大范围单宽流量的泄洪消能工况。试验研究表明,在台阶尺寸一定的情况下,水流旋滚起始位置和充分掺气位置随单宽流量的增加而沿流向向下游下移。在陡坡段上端设置由小到大的过渡台阶能够有效改善阶梯进口段水流流态。根据实测流速,从传统水力学角度出发,对陡坡段阶梯的消能率进行了计算和分析,得出了消能率与台阶尺寸、单宽流量变化的关系：台阶尺寸一定时,阶梯溢流的消能率随流量(或单宽流量)的增大而减小,且消能率并不是随下泄流量的增大而线性减小,而是随流量的增大,消能率的减小速度会变慢；单宽流量不变时,消能率随台阶尺寸的增大而增大。长陡坡无压隧洞采用沿程消能的阶梯消能措施,能够有效降低洞内沿程水流流速,简化下游消能设施,以大大减小下游消力池的尺寸或省去消力池,从而可以大量节省工程投资。是值得采用和推广的长陡坡无压隧洞内流消能措施。更多还原

【Abstract】 In order to search the suitable energy dissipation measures in the long free-flow tunnel with steep slop, the energy dissipation by steps set on the bottom of the tunnel is put forward. Based on both the theory analysis and the scaled model experiments, the flow characteristics and energy dissipation effect in the tunnel with steep slop are investigated. The necessity of the energy dissipation by hydraulic jump on the end of the steep tunnel is experimented and discussed.The experimental observation and analysis show that the suitable type of steps and their size are the key factors to obtain the good flow patterns in the steep stepped tunnel. For the large ranges of unit flow discharges, the good flow pattern, the skimming flow, can be formed on the certain suitable steps in the tunnel for a long distance.For a certain step size, the experimental results show that both the beginning water rolling on the steps and the aeration point on the flow surface move down along the flow course with the increase of unit flow discharge. The several transition steps from small size to big size set on the start section of the steep tunnel can improve the flow pattern on this section.According to the measured velocity on the model, from the view of traditional hydraulics, the energy dissipation rate is calculated and analyzed. For a certain step size, the energy dissipation rate decreases quickly at first and then slowly with the increase of unit discharge and their relation is not linear. If unit discharge is unchanged, the energy dissipation rate increases with the increase of the step size.For the energy dissipation measure by steps set on the bottom of the long steep tunnel, flow velocity in the tunnel can be greatly reduced. The size of stilling basin can be small or even be not needed, so the investment of the project will be saved. This energy dissipation measure is worthy to put to use and promote for long free-flow tunnels with steep slop.更多还原