PyroCLAST: a new experimental framework to investigate overspilling of channelized, concentrated pyroclastic currents
PyroCLAST: a new experimental framework to investigate overspilling of channelized, concentrated pyroclastic currents
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DOI：
10.1007/s00445-022-01623-y
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发表时间：
2022-12
影响因子：
3.5
通讯作者：
V. Gueugneau;S. Charbonnier;O. Roche
中科院分区：
文献类型：
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作者：
V. Gueugneau;S. Charbonnier;O. Roche
当小体积的集中火山碎屑流 (CPC) 遇到传播方向的突然变化时，通常会导致通道范围内发生意外且致命的溢出。我们展示了通过新的实验设施 PyroCLAST 获得的第一个结果，该设施是为了研究此类溢出的机制而建造的。该装置由一个5米长的水槽组成，在距水源的中间距离处有45°的谷弯，其倾斜角从3°到15°不等。直径为 45–90 µm 的玻璃珠最初在储液器中流化，并通过垂直滑动门快速释放到水槽中。使用摄像机记录实验，并使用粒子图像测速仪测量母通道化和漫滩流速和排放率的时间演变。当水流与坡度为 9 至 15° 的弯道相互作用时，就会产生溢出，产生前溅水和溢流。结果表明，坡度角通过增加流量排放速率有利于溢流的形成，导致沿超过通道侧壁的弯曲（即超高）的流量厚度局部增加。此外，在恒定的初始条件下，高的渠道坡度角和流量有利于离散的内部流动脉冲的发展，并且发现渠道化流量的跳动与河岸沉积物的跳动之间呈正相关。本研究收集的数据也将构成未来 CPC 数值模型基准测试的参考数据集。
Small-volume concentrated pyroclastic currents (CPCs) are often responsible for unpredicted and deadly overspills from channel confines when they encounter an abrupt change in propagation direction. We present the first results obtained with a new experimental facility, PyroCLAST, built to investigate the mechanisms of such overspills. The apparatus consists of a 5-m-long flume with a 45° valley bend at mid-distance from the source, and whose slope angle varies from 3 to 15°. Glass beads of 45–90-µm diameter are initially fluidized in a reservoir and rapidly released into the flume through a vertical sliding gate. Experiments are recorded using video cameras to measure the temporal evolution of both the parent channelized and overbank flow velocity and discharge rate, using particle image velocimetry. Overspills are generated when the flows interact with the bend, at slope angles of 9 to 15°, generating a front splash and an overbank flow. Results demonstrate that the slope angle favors the formation of overspill by increasing the flow discharge rate, causing a local increase of the flow thickness along the bend (i.e., superelevation) that overtops the channel sidewall. Moreover, under constant initial conditions, a high channel slope angle and discharge rate favor the development of discrete, internal flow pulses, and a positive correlation is found between the runout of the channelized flows and that of overbank deposits. Data collected in this study will also constitute a reference dataset for future benchmarking of CPC numerical models.