【摘要】 本文介绍了如何利用有限元法来计算管道边墙突体绕流的速度和压力分布,计算了下列各种突体的压力分布和最小压力系数:(1)不同相对突体高度和圆弧半径条件下的圆弧弓形和半弓形突体;(2)不同相对突体高度、圆化半径和坡度条件下的圆化三角形和斜坡形突体;(3)不同突体间距和个数条件下的多个突体。压力分布和最小压力系数的试验结果与计算结果吻合较好,最小压力系数和变压水洞中实测的初生空化数也很接近。文中系统地给出了最小压力系数与相对突体高度或突体坡度之间的关系曲线,根据这些曲线即可估算相应突体的初生空化数。由于各种突体圆化后能明显地降低初生空化数,因此对过流表面上的不平整突体应进行磨圆处理。通过计算对比,文中还给出了由于浇筑混凝土的模板等施工原因造成的多个突体,也可按单个突体的数据来估计它的初生空化数。更多还原

【Abstract】 A general review is given on the method of computing the velocity and pressure distribution along surface irregularities on the bottom of a pressure conduit by finite element method. The pressure distribution and minimum pressure coefficients Cpmin have been computed, covering different kinds of irregularities such as with:1. different heights A and radii of the circular arc R; 2.different heights, radii of the rounded corner and slopes of the irregularity x/y;3.different spacings l and number of distributed irregularities n.The computational and experimental results fairly agree. Curves showing Cpmin versus R/Δ or x/y are presented, from which the incipient cavi-tation number can be evaluated. In order to decrease the incipient cavita-tion number of surface irregularity, thus to prevent cavitation erosion, rounding off the sharp corners ought to be necessary.更多还原