高拱坝坝身泄洪雾化数值预报方法验证分析

Verification and analysis of the numerical prediction method for flood discharge atomization at the orifice of a high arch dam

数学模型应用于高拱坝坝身泄洪雾化预报,一直缺少原型观测资料的系统验证,分析结果可靠性存疑。本文基于小湾水电站拱坝的孔口泄洪雾化实测数据,针对数学模型的随机溅水基本理论进行验证,针对海拔高程与气温影响进行敏感性分析。研究表明:通过综合考虑泄洪风场、大坝、河谷地形、海拔与气温等因素共同影响,数学模型可以真实反映泄洪雾化空间风场与降雨强度变化,其可靠性满足工程实践要求;数学模型的降雨强度分析值与实测值相对误差在10%以内,在降雨强度较大的核心区,数学模型的相对误差较小,在降雨强度较小的远区,相对误差较大,原因在于随机数学模型分析过程中,雾化核心区内雨滴数量众多,统计结果更加精确;海拔高程与气温的上升,使得泄洪雾化区内降雨强度分布坦化,一般以降雨强度300~500 mm/h为界,低于该值的区域,海拔高程每上升1000 m,降雨强度增幅20 mm/h,气温每上升10℃,降雨强度增幅8 mm/h;由于实际工程岸坡主要分布于200 mm/h以下地区,因此气象条件的影响不容忽视。

The mathematical model applied to the flood discharge atomization prediction of high arch dams still lacks the verification of the prototype observation data,and the reliability of the analysis results is doubtful.Therefore,the systematic verification and analysis have been conducted on the stochastic splash simulation theory and method of the mathematical model,based on the field atomization observation data of the dam orifice operation in Xiaowan hydropower station.The sensitivity analysis on the influence of altitude and temperature on the atomized rainfall distribution was also conducted.The research result has shown that:(1)By comprehensively considering the combined effects of factors such as flood discharge wind field,dam,valley topography,altitude,and temperature,the mathematical model can really reflect the change of wind field and rain intensity in the discharge atomization space,and its reliability meets the requirements of engineering practice.(2)The relative error between the analysis value and the measured value of rainfall intensity is less than 10%.In the core region with high rainfall intensity,the calculation error of the mathematical model is small,and in the far region with low rainfall intensity,the error is relatively large.The reason for this is that during the analysis process of the stochastic mathematical model,there are more dense raindrops in the atomized core area,so the statistical results are more accurate.(3)The rise of altitude and temperature flattens the longitudinal distribution of atomized rainfall,and the partition value of rainfall intensity is generally 300-500 mm h.In the region below the value,the rainfall intensity increases by 20 mm h for every 1000m rise in altitude,and increases by 8mm h for every 10℃rise in temperature.In practical engineering,the bank slope atomization protection area is mainly distributed in the area below 200 mm h,so the influence of meteorological conditions can not be ignored.