摘要
为研究弯道出流横向流速的衰减规律,通过量纲分析建立了量纲一衰减长度的经验公式,采用系列数值试验的结果率定了该经验公式,分析了各因素影响程度以及衰减长度分布规律,并与理论公式进行了对比。试验发现雷诺数Re和弗劳德数Fr对衰减长度影响极小;衰减长度,横向上凹岸区最大,中间次之,凸岸区最小;垂向上近底区最大,近水面区次之,最小值位于中间。典型理论公式计算的衰减长度的垂向分布,与试验结果定性一致,但由于忽略横比降的影响,导致其在近底区偏小。结果表明:该经验公式考虑因素较理论公式更为全面;衰减长度在不同区域不同;采用相似模型研究弯道出流的环流衰减长度时,需要保证阻力相似,但一定条件下,可以放弃Fr和Re相似。
The attenuation process of transverse velocity in the straight outlet section downstream of a bend was investigated. An empirical equation of dimensionless attenuation length （DAL） was established via dimensional analysis. A series results of numerical experiments were adopted to calibrate this equation, as well as to analyze the impact of all factors and the distribution law of DAL. In addition, results were compared with theoretical predictions. The experiments show that Re and Fr have little effect on DAL. Horizontally, the DAL in concave-bank zone is the largest, followed by that in central zone, and the minimum value is in convex-bank zone. Whereas, vertically its value in near-bottom zone is the largest, followed by that in near-surface zone, and the minimum value is in central zone. The vertical distribution of DAL predicted by a typical theoretical equation is qualitatively in accordance with the experimental result. However, disregarding the impact of transverse slope caused its under-prediction near the bottom. Results show that considerations of the empirical equation in this paper are more comprehensive than those of the theoretical equations, and DAL varies horizontally and vertically. When using hydraulic model to investigate the attenuation process of transverse velocity, the similarity law of resistance should be followed, whereas the similarity law of Fr and Re can be neglected at specific conditions.
出处
《水科学进展》
EI
CAS
CSCD
北大核心
2014年第3期392-400,共9页
Advances in Water Science
基金
国家自然科学基金资助项目(51109194
51039004)~~
关键词
弯道出流
流速衰减
数值模拟
量纲分析
相似律
bend outflow
velocity attenuation
numerical simulation
dimensional analysis
similarity law
