组合面Combination of surface
水工建筑物中某些局部结构的表面常由几种曲面和平面相交或相切组合而成,这种表面称为组合面,如图9.29中的引水管进口和尾水管。水电站及抽水机站的引水管道或隧洞通常是圆形断面,而安装闸门处需要做成矩形断面。为使水流平顺过渡,在矩形断面与圆形断面之间,通常采用渐变段过渡,使断面逐渐变化,如图9.30所示。
The surface of some local structures in hydraulic buildings is usually formed by several curved surfaces and intersecting or tangential combinations of planes, which is called composite surface, as shown in FIG. 9.29, water inlet and draft pipe. The diversion pipes or tunnels of hydropower stations and pumping stations are usually circular sections, while rectangular sections are needed at the installation of gate gates. In order to smooth the transition of water flow, a transition section is usually used between the rectangular section and the circular section to gradually change the section, as shown in FIG. 9.30.

详细分析渐变段表面的组成和电站尾水管弯曲段表面的组成。
The composition of the surface of the gradient section and the curved section of the draft tube of the power station are analyzed in detail.

