中文摘要：

引言 孔结构参数是孔射流的重要影响因素之一，相关文献报道主要涉及孔径板厚比d／t对孔流系数Co的影响，也有文献报道了孔倾角的影响，其他孔结构参数的研究未见报道。因此，本项目开展了不同孔结构参数下孔流特性的系统研究。前期工作首先考察了d和t对垂直圆孔射流的影响，研究结果表明，d和t对Co的作用是协同的，

英文摘要：

The behavior of the fluid flowing through vertical sharp-edged orifices with the same crosssection area but different geometry was investigated experimentally on typical ＂large orifice＂ and ＂small orifice＂ . The profiles of orifice discharge coefficient curves of circular, elliptical, square, rectangular and triangular orifices were similar, and the profile of the circular one is the highest and that of the triangular one is the lowest. It can be concluded that the orifice＇s geometry has some effect on orifice discharge, but it is not the key parameter, because it doesn＇t change the orifice＇s flow mechanism essentially. The effects of the orifice＇s geometry on energy losses were evaluated based on the analysis of the hydraulic radius of orifice, interfacial tension in acute angle, and penetrating phenomenon of jet flow through non-circular orifices, which might complement the flow mechanism of the circular orifice the authors studied before. Afterwards, the orifice flow was simulated with CFD software Fluent 6.2 in order to investigate the effect of orifice＇s geometry on velocity distribution and energy losses of orifice discharge. It can be seen from the simulated flow field that the geometry of orifice had little effect on the overall range and velocity distribution of the contributing flow region in front of the orifice, and the energy dissipation in front of the orifice still could be calculated by the hemisphere model. It may help to understand that the difference of mechanical energy losses in orifice flow appears after flowing into the orifice.