Abstract Cavitation phenomena, produced when a flow is accelerated through a restriction, are of fundamental importance because of the large pressure oscillation they induce on pipelines. This paper presents an experimental investigation of various cavitation regimes produced at the exit of an orifice and its downstream propagation and attenuation. A cylindrical and a conical orifice are investigated over a range of cavitation number σ = 0.2 - 1 , keeping the ratio between saturation pressure ( P sat ) and downstream pressure ( P dw ) at two different values ξ = P sat / P dw = 0.05 , 0.3 . The range of operating conditions allows to investigate cavitation from the inception to the cloud, the developed, and the super-cavitation regime. For each configuration, the experimental analysis includes flow rate measurements, pressure signals via fast pressure transducers, and high-speed videos. The videos are analyzed using Multiscale Proper Orthogonal Decomposition (mPOD), to extract the coherent patterns that arise during the cloud cavitation and the developed cavitation regimes. The simultaneous analysis of the high-speed video in the proximity of the orifice and the time-resolved downstream pressure signal allows highlighting the effect of the cavitation intensity on the downstream evolution of these fundamental flows.

中文翻译：

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通过孔板的空化流的光谱和模态分析

摘要 当流动通过限制加速时产生的气穴现象具有重要意义，因为它们会在管道上引起大的压力振荡。本文介绍了在孔口出口处产生的各种空化状态及其下游传播和衰减的实验研究。在空化数 σ = 0.2 - 1 的范围内研究圆柱形和锥形孔口，将饱和压力 ( P sat ) 和下游压力 ( P dw ) 之间的比率保持在两个不同的值 ξ = P sat / P dw = 0.05 , 0.3 . 操作条件的范围允许研究从开始到云、发展和超级空化状态的空化。对于每种配置，实验分析包括流速测量、压力信号通过快速压力传感器和高速视频。使用多尺度适当正交分解 (mPOD) 分析视频，以提取在云空化和发展的空化机制期间出现的相干模式。孔口附近的高速视频和时间分辨的下游压力信号的同时分析可以突出空化强度对这些基本流动的下游演变的影响。