Flow patterns in upstream and downstream straight tubes of sudden-changed areas in a horizontal straight pipe were experimentally examined. Both sudden-expansion cross-section (SECS) and sudden-contraction cross-secti...Flow patterns in upstream and downstream straight tubes of sudden-changed areas in a horizontal straight pipe were experimentally examined. Both sudden-expansion cross-section (SECS) and sudden-contraction cross-section (SCCS) were investigated. The flow pattern maps upstream and downstream were delineated and compared with those in straight tubes with uniform cross-sections. The effects of the SECS and SCCS on flow patterns were discussed and analyzed. Furthermore, flow pattern transition mechanisms resulting in occurrences of different flow patterns were simply discussed and some transition criteria for the flow pattern transitions were deduced by using the non-dimensionlized analysis method.展开更多
溢流坝下游收缩断面水深 hc 的计算对水工消能设计十分重要． 目前常用的方法有试算法、图解法和迭代法，这些方法计算精度不高，人工计算量大或要求较高的计算数学的理论知识等，不便于在生产实际中推广应用． 为此，把 hc 的计算问题...溢流坝下游收缩断面水深 hc 的计算对水工消能设计十分重要． 目前常用的方法有试算法、图解法和迭代法，这些方法计算精度不高，人工计算量大或要求较高的计算数学的理论知识等，不便于在生产实际中推广应用． 为此，把 hc 的计算问题归结为非线性优化问题，用作者研制的加速遗传算法 （AGA） 来处理． 应用 AGA 方法的实例计算结果说明 AGA 比常用方法简便 计算精度高且具有通用性．展开更多
基金the National Natural Science Foundation (No.59995460)
文摘Flow patterns in upstream and downstream straight tubes of sudden-changed areas in a horizontal straight pipe were experimentally examined. Both sudden-expansion cross-section (SECS) and sudden-contraction cross-section (SCCS) were investigated. The flow pattern maps upstream and downstream were delineated and compared with those in straight tubes with uniform cross-sections. The effects of the SECS and SCCS on flow patterns were discussed and analyzed. Furthermore, flow pattern transition mechanisms resulting in occurrences of different flow patterns were simply discussed and some transition criteria for the flow pattern transitions were deduced by using the non-dimensionlized analysis method.
文摘溢流坝下游收缩断面水深 hc 的计算对水工消能设计十分重要． 目前常用的方法有试算法、图解法和迭代法，这些方法计算精度不高，人工计算量大或要求较高的计算数学的理论知识等，不便于在生产实际中推广应用． 为此，把 hc 的计算问题归结为非线性优化问题，用作者研制的加速遗传算法 （AGA） 来处理． 应用 AGA 方法的实例计算结果说明 AGA 比常用方法简便 计算精度高且具有通用性．
