通过相对比能计算台阶式溢洪道水头损失的研究

Calculation of head loss over stepped spillways with relative specific energy

水流比能是重要的水力参数,反映水流运动部分的能量。将台阶溢洪道与光滑溢洪道的断面比能进行对比分析,引入台阶相对比能的概念,准确反映台阶溢洪道与光滑溢洪道水头损失之间的差别。通过26.6?~48.0?坡角、0.5m^2.0m台阶高度的21组模型试验,分析了台阶溢洪道比能及相对比能与流程长度、单宽流量、台阶高度、坡度之间的关系。台阶溢洪道水流比能与这些参数关系比较复杂,不便分析应用,而台阶溢洪道相对比能与流程长度呈良好的线性关系而且斜率与单宽流量无关,与台阶高度、坡度呈递增关系,便于分析应用,试验资料证实了引入台阶溢洪道相对比能的必要性。提出计算台阶溢洪道水头损失的经验公式,为相关设计提供参考。

Specific energy is a foremost hydraulic parameter of stepped spillways, a measure of kinematic energy of moving water. This paper compares specific energies between stepped spillway and smooth spillway, and works out a new concept--relative specific energy that describes the difference of head loss between the two spillways. Model tests on skimming flows of 21 sets were conducted using a spillway slope range of 26.6°-48° and a step height range of 0.5-2.0m, focusing on the variations of specific energy and relative specific energy with the length of flow path, unit discharge, step height, and bottom slope. The results indicate that the specific energy varies with these parameters in a manner too complicated to apply practically while the relative specific energy that is independent of discharge, varies linearly with the length of flow path. Step height has a great influence on the relative specific energy that increases with it and spillway slope. The results prove the necessity of stepped spillway analysis adopting relative specific energy and its advantage in practical applications. An empirical formula for calculation of water head loss is given.