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首页> 外文期刊>Experimental Thermal and Fluid Science: International Journal of Experimental Heat Transfer, Thermodynamics, and Fluid Mechanics >A comparative study of natural and ventilated supercavitation across two closed-wall water tunnel facilities
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A comparative study of natural and ventilated supercavitation across two closed-wall water tunnel facilities

机译：两种闭式墙隧道设施的自然和通风超洞穴的比较研究

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Despite half a century of experimental investigation into both natural and ventilated supercavitation, there are still significant discrepancies among the results, in terms of supercavity geometry and ventilation demand, etc., under approximately similar conditions from different water tunnel facilities. To understand the influences of the flow facilities on the supercavitation experiments, a systematic comparison is conducted using the results from two closed-wall water tunnels, i.e. the Saint Anthony Falls highspeed water tunnel and the Chuangnam National University Closed Tunnel. For both ventilated and natural supercavitation, the experimental conditions from the two facilities are designed to match over a wide range of Froude number and blockage ratio, etc. For the ventilated supercavitation, the cavitation number for generating a ventilated supercavity and the hysteresis process for sustaining a supercavity show a proper match across the two facilities while holding the Froude number and blockage ratio constant. However, the ventilation demand to form a supercavity shows a noteworthy difference across the facilities even under the same Froude number and blockage ratio. Such a difference in the ventilation requirement is attributed to the mismatch of Reynolds number, the detailed geometry of the cavitator models as well as the test section which influences the pressure distribution along the span of the super cavity. Similarly, for natural supercavitation, both facilities yield a similar vaporous cavitation number for the supercavity formation under the same Froude number and blockage ratio, as well as similar choking behavior, i.e. cavitation number stays constant despite the decrease of test section pressure once a natural supercavity forms. The theoretical analysis of the choking phenomenon explains the trend of cavitation number under choking and its dependence on cavitator geometry, Froude number as well as the pressure loss in the water tunnel. A geometry comparison is conducted for both natural and ventilated supercavities in the two facilities under the same Froude number, blockage ratio and cavitation number. The comparison results show differences in the normalized cavity total length across different facilities as well as supercavity types despite the similarities in the supercavity maximum diameter and half-length. These differences were attributed to the variance in the pressure and flow distributions from the different facilities and across ventilated and natural supercavitation. The natural supercavities from the two facilities are further compared with the estimated natural supercavitation in unbounded flow under the same cavitation conditions. The comparison result highlights the limitation of the conventional theory in capturing the cavity geometries in actual experiments. (C) 2017 Elsevier Inc. All rights reserved.
机译：尽管有半个世纪的实验调查既有天然通风超级潜力，但在超级沟壑几何和通风需求等方面仍存在显着的差异，在不同水隧道设施的大致相似条件下。要了解流动设施对超级渗流实验的影响，使用来自两个闭墙水隧道的结果进行系统的比较，即Saint Anthony瀑布高速水隧道和Chuangnam国家大学封闭隧道。对于通风和自然的超级挖掘，两个设施的实验条件旨在匹配通风超洞穴的广泛的FRoude号码和封闭比例等，用于产生通风超级沟壑的空化号和用于维持的滞后过程超级障碍在两个设施中显示适当的匹配，同时持有FRoude号码和阻塞比常数。然而，即使在相同的Froude号和封闭比例下，形成超级胸腔的通风需求表明了整个设施中的值得注意。通风需求的这种差异归因于雷诺数的不匹配，空穴模型的详细几何形状以及影响沿超级腔的跨度的压力分布的测试部分。类似地，对于天然超级挖掘，两个设施在相同的Froude号和堵塞比下，除了类似的窒息行为，即相同的窒息行为，即仍然是试验部分压力一旦天然超级障碍减少，空化数保持不变。形式。窒息现象的理论分析解释了窒息下的空化数及其对空穴几何，FRoude号码以及水隧道压力损失的依赖性。在相同的FRoude号码，阻塞比和空化数下，为两种设施中的天然和通风超级挤压性进行几何比较。比较结果表明，尽管超级沟率最大直径和半长度的相似性，但是在不同设施上的归一化腔总长度的差异差异。这些差异归因于来自不同设施的压力和流量分布的方差，以及通风和天然超级挖掘机。与在相同的空化条件下，两种设施的自然超级耐受者进一步与估计的自然超级空间相比。比较结果突出了传统理论在实际实验中捕获腔几何的限制。 （c）2017年Elsevier Inc.保留所有权利。

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