基于CCHE的重力沉砂池结构布置参数比选研究

为了提高重力沉砂池水沙分离效率,对重力沉砂池相关结构参数进行优化使各项结构参数取得较优值,并研究了侧向溢流堰长度与位置对重力沉砂池最终水沙分离效率的影响,且取得较优的侧堰长度与位置。基于CCHE软件采用混合掺长紊流模型建立CCHE2D重力沉砂池数学模型,得到重力沉砂池内水流流速、泥沙沿程分布及最终水沙分离效率,在已有研究成果基础上分析得到较优的重力沉砂池侧向溢流堰长度及位置。研究结果表明:改变侧向溢流堰长度及位置可将传统重力沉砂池水沙分离效率显著提高。当溢流堰长度取4 m并向上游移动1 m时可将水沙分离效率提高至71.20%。当侧向溢流堰向上游移动一段距离可以阻挡由沉砂池末端产生回流、漩涡等流态而卷起的泥沙,避免其流向清水池,从而提高重力沉砂池水沙分离效率。移动距离不可过前,否则距离过于靠前由于沉砂池边壁的阻挡容易使沉砂池末端形成一段"死水区",使沉砂池有效沉降距离减少,从而降低重力沉砂池水沙分离效率。

CCHE-based study on parameter comparison and selection for structural layout of gravity sedimentation basin

In order to enhance the efficiency of water and sediment separation in gravity sedimentation basin，the relevant structural parameters of gravity sedimentation basin are optimized，and then better values of all the structural parameters are obtained， while the influence from the length and the position of lateral overflow weir on the final separation efficiency of water and sediment in gravity sedimentation basin is studied，from which better length and position of the weir are obtained． Based on the CCHE ( center for computation hydroscience and engineering model) ，the mathematical model CCHE2D for gravity sedimentation basin is established with the hybrid mixing-length turbulent model，and then the flow velocity，the on-way distribution and the watersediment separation efficiency inside gravity sedimentation basin are obtained，thus the better length and the position of lateral overflow weir are obtained from the analysis made on the basis of the existing study results concerned． The study result shows that the water-sediment separation efficiency of the conventional gravity sedimentation basin can be significantly enhanced by means of changing both the length and the position of lateral overflow weir． When the length of 4m is taken for the overflow weir and the weir moves upstream by 1m，the water-sediment separation efficiency can be increased up to 71. 20%． When the lateral overflow weir moves upstream by a certain distance，the turbulent sediment rolled up by the flow patterns of backflow，vortex，etc． at the end of sedimentation basin can be blocked for avoiding it flowing into clean-water basin，thus enhancing the water-sediment separation efficiency of gravity sedimentation basin． The moving distance cannot be too far ahead，otherwise a dead-water zone is prone to be formed at the end of the sedimentation basin due to the blocking of the side wall of the basin and makes the effective settling distance decreased，and consequently decreases the water-sediment separation efficiency of gravity sedimentation basin as well．