強制跳水に関する研究(1) ―台形副ダムによる跳水特性―

Abstract

"Forced hydraulic jump" is defined as a jump which is formed forcibly by the stillingbasin appurtenances when the jump would he swept out due to insufficient tailwater depth.Although a great number of tests have been conducted on hydraulic-jump-type stilling basinswith various appurtenances, up to date, analytical data are not enough to explain the flowbehaviours in the basin and to develop a general design procedure of the structures.The object of the study described herein is to investigate the performance of the secondarydam with a trapezoidal shape under overflow condition, which is widely used as the stillingbasin structures of the flood-control projects. It is a peculiar phenomena exhibited in thistype of the basin that a stable jump formed in the basin abruptly changes into supercritical flowcondition at a certain discharge increase, and vice versa. In this paper, the flow characteristicsunder these critical states which represent a transition region between a normal jump and a"forced jump", are presented. Under a "jump-spray" critical state, the experimental datashows that a stable jump is formed in smaller length than that of a normal jump and that thepressure terms included in the momentum equations should be compensated for hydrostaticpressure distribution. Under "spray-jump" critical state, the theoretical solutions based onthe momentum and energy equations show good agreement with the experimental results.