Stochastic Uncertainty in a Dam-Break Experiment with Varying Gate Speeds
Stochastic Uncertainty in a Dam-Break Experiment with Varying Gate Speeds
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DOI：
10.3390/jmse9010067
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发表时间：
2021-01
影响因子：
2.9
通讯作者：
H. Takagi;F. Furukawa
中科院分区：
文献类型：
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作者：
H. Takagi;F. Furukawa
在溃坝水流试验中，由于试验过程繁琐，很少对闸门开启速度的固有特性进行研究。对于这些机制的随机分析，本研究涉及290个流量测试，通过不同的门速度在0.20和2.50米/秒之间的水槽中进行的溃坝;四个压力传感器嵌入在水槽床记录高频底部压力。对获得的数据进行处理，以确定浇口速度和最大压力之间的统计关系。它们之间的相关性在离门最近的传感器（Ch 1）和离门最远的传感器（Ch 4）处特别显著，皮尔逊系数r分别为0.671和-0.524。四分位距（IQR）表明，最大压力的统计变异性在Ch 1最大，在Ch 4最小。当闸门打开得更快时，闸门附近会出现更高的压力和更大的不确定性。然而，压力大小和不确定性都随着溃坝流向下游传播而减小。最大压力出现在长期波动压力阶段;然而，被认为是统计异常值的实例出现在短期和脉冲压力阶段。通过使用高速摄像机图像进行的目视分析，还发现了一些可能导致底部压力显著变化的独特现象。例如，爆炸性水射流在闸门提升后立即增加垂直加速度，从而延缓溃坝水流的传播。由于侧壁的存在，产生了两个边缘波，其表现类似于船舶尾流，导致水流的强烈水平混合。
Uncertainties inherent in gate-opening speeds are rarely studied in dam-break flow experiments due to the laborious experimental procedures required. For the stochastic analysis of these mechanisms, this study involved 290 flow tests performed in a dam-break flume via varying gate speeds between 0.20 and 2.50 m/s; four pressure sensors embedded in the flume bed recorded high-frequency bottom pressures. The obtained data were processed to determine the statistical relationships between gate speed and maximum pressure. The correlations between them were found to be particularly significant at the sensors nearest to the gate (Ch1) and farthest from the gate (Ch4), with a Pearson’s coefficient r of 0.671 and −0.524, respectively. The interquartile range (IQR) suggests that the statistical variability of maximum pressure is the largest at Ch1 and smallest at Ch4. When the gate is opened faster, a higher pressure with greater uncertainty occurs near the gate. However, both the pressure magnitude and the uncertainty decrease as the dam-break flow propagates downstream. The maximum pressure appears within long-period surge-pressure phases; however, instances considered as statistical outliers appear within short and impulsive pressure phases. A few unique phenomena, which could cause significant bottom pressure variability, were also identified through visual analyses using high-speed camera images. For example, an explosive water jet increases the vertical acceleration immediately after the gate is lifted, thereby retarding dam-break flow propagation. Owing to the existence of sidewalls, two edge waves were generated, which behaved similarly to ship wakes, causing a strong horizontal mixture of the water flow.