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琴键堰(P.K堰)是目前水库大坝溢洪道升级改造新技术中出现的堰型,它能有效解决现有水库极端致灾因子条件下泄流能力急剧增加的问题。设计P.K堰首先要研究其泄流能力特性,它直接关系到PMF条件下最大水库水位或库容的确定。本文首先对最近两年发表的P.K堰泄流能力公式进行了对比,然后结合已有试验数据,通过量纲分析和多参数优化,给出了推荐公式,并利用该公式对P.K堰的泄流特性和超泄能力进行了研究。结果表明,当上游水头较小,一般H/P<0.2时,P.K堰流量系数较大,超泄比系数大于3,泄流量增量比较明显,随着上游水头的增大,堰的总宽度对泄量起主要作用,其泄量增大的优势也越来越弱,实用范围内的超泄比在1.2~3.5之间。本文给出公式的预测值跟已发表的试验值符合良好,平均误差在5%~8%,比Machiels公式误差更小,该公式可供P.K堰泄流能力评估和优化设计时参考。
The piano weir (P.Kirn) is a weir type in the new technology of the spillway upgrading and renovation of the reservoir dam, which can effectively solve the problem of drastic increase of the discharge capacity under the existing extreme disaster hazard factor of the reservoir. Design P.K weir first to study its discharge capacity characteristics, which is directly related to the determination of the maximum reservoir water level or storage capacity PMF conditions. In this paper, we firstly compare the discharge capacity of PK weir published in the last two years. Then, combining with the existing experimental data, we give the recommended formula through dimension analysis and multi-parameter optimization, Properties and over-venting capacity were studied. The results show that when the upstream head is small and the general H / P <0.2, the flow coefficient of the PK weir is larger and the coefficient of excess discharge is more than 3, and the discharge increment is obvious. As the upstream head increases, the total width of the weir Plays a major role in the discharge, the advantage of its increased discharge is getting weaker and harder, within the practical range of the venting ratio between 1.2 ~ 3.5. In this paper, the predicted value of the formula is in good agreement with the published test values. The average error is between 5% and 8%, which is smaller than the Machiels’ formula. This formula can be used as a reference for the assessment and optimization design of the discharge capacity of P.Kyan.