Abstract Transformation of flow turbulence structure with cavitation occurrence, determination of the flow conditions favorable for nucleation of cavitation bubbles, influence of the statistical structure of turbulence on this process and the inverse effect of cavitation on the flow dynamics are challenging problems in modern fluid mechanics. The paper reports on the results of statistical processing of the velocity fields measured by a PIV technique in cavitating flow over a 2D symmetric hydrofoil for four flow conditions, starting from a cavitation-free regime and finishing by unsteady cloud cavitation. We analyze basic information on the statistical structure of velocity fluctuations in the form of histograms and Q-Q diagrams along with profiles of the mean velocity and turbulent kinetic energy. The research reveals that the flow turbulence pattern and distributions of turbulent fluctuations change significantly with the cavitation development. Under unsteady cloud cavitation conditions, the probability density function of the fluctuating velocity has a two-mode distribution, which indicates switching of two alternating flow conditions in a region above the hydrofoil aft part due to periodic passing of cavitation clouds. Behaviors of the mean and most probable velocities unexpectedly appear to be different with a monotonous increase of the incoming flow velocity. This finding must be caused by modification of the skewness coefficient of the fluctuating velocity.

中文翻译：

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二维水翼周围空化流速度场的统计结构

摘要 空化发生时流动湍流结构的转变、有利于空化气泡形核的流动条件的确定、湍流统计结构对这一过程的影响以及空化对流动动力学的反作用是现代流体力学中具有挑战性的问题。该论文报告了对通过 PIV 技术测量的速度场的统计处理结果，这些速度场在 2D 对称水翼上的空化流中有四种流动条件，从无空化状态开始，到不稳定云空化结束。我们以直方图和 QQ 图的形式分析速度波动统计结构的基本信息，以及平均速度和湍流动能的轮廓。研究表明，随着空化的发展，流动湍流模式和湍流波动的分布发生了显着变化。在非定常云空化条件下，脉动速度的概率密度函数具有双模态分布，这表明由于空化云的周期性通过，水翼船尾部上方区域的两种交替流动条件发生了切换。平均速度和最可能速度的行为出乎意料地似乎随着进入流速的单调增加而不同。这个发现一定是由波动速度的偏度系数的修改引起的。脉动速度的概率密度函数具有双模态分布，表明由于空化云的周期性通过，水翼船尾上方区域的两种交替流动条件发生了切换。平均速度和最可能速度的行为出乎意料地似乎随着进入流速的单调增加而不同。这个发现一定是由波动速度的偏度系数的修改引起的。脉动速度的概率密度函数具有双模态分布，表明由于空化云的周期性通过，水翼船尾上方区域的两种交替流动条件发生了切换。平均速度和最可能速度的行为出乎意料地随着进入流速的单调增加而不同。这个发现一定是由波动速度的偏度系数的修改引起的。