冲刷漏斗纵剖面形态数值模拟技术研究

提出σ坐标系垂向分层的优化方法,较好地解决了传统σ坐标变换用于底孔泄流数值模拟时存在网格边界变化的问题;采用一维水流模型为立面二维模型提供自由水面边界,即"动刚盖法"确定自由表面;根据坝前趋孔水流的流动特性和水下纵坡稳定性受力分析,分别导出σ坐标系下床面泥沙边界条件和底孔泄流初期河床滑塌的判别式。在此基础上建立底孔泄流条件下立面二维水流泥沙数学模型,并将之应用于有刚性护坦条件下冲刷漏斗形成的数值模拟。模拟结果表明,漏斗冲刷平段长度、漏斗纵坡等数值试验结果与水槽试验基本一致,验证了模型的合理性和可靠性。

Numerical simulation study on longitudinal profile of scouring funnel

An optimized method is put forward for the conventional sigma coordinate system which will cause a dynamical change size of an orifice and have difficulty in the specifying the free surface boundary condition.And 1D flow model is adopt ed to determine the vertical 2D free surface boundary, namely, "movable rigid-lid" used to get the boundary condition.Based on the flow characteristic in front of the bottom orifice and stability analysis of the underwater slope, it introduces the boundary condition of sediment exchange near the riverbed and the expression for the critical condition of riverbed sliding in the initial stages of the bottom orifice outflow respectively.So a vertical 2D flow and sediment mathematical model for bottom orifice outflow is proposed.It is validated by the flume experimental data for the riverbed deformation of scouring funnel shape with rigid apron.Satisfactory agreement is obtained in the length of scouring even segment and the slope of scouring funnel.It shows the rationality and reliability of this proposed model.