Purpose

This paper aims to focus on the cavitating flow around the Clark-Y hydrofoil when the dissolved air is taken into account as the third phase. As the RNG k-epsilon model yields poor prediction due to overestimation of viscosity, the modification approaches including density corrected method, filter-based model and filter-based density correction model are used, and the turbulence model is modified. Also, the numerical results are compared with the experimental data.

Design/methodology/approach

The cavitating flow is known as a complex multi-phase flow and appeared in the regions where the local pressure drops under saturation vapor pressure. Many researches have been conducted to analyze this phenomenon because of its significant impact on the erosion, vibration, noise, efficiency of turbomachines, etc.

Findings

The experiments are conducted in a rectangular test section equipped with Clark-Y hydrofoil providing cavity visualization, instantaneous pressure and vibration fluctuations. The simulations are carried out for different cavitation numbers with and without dissolved air. The Fast Fourier Transform, continues wavelet transform and temporal-spatial distribution of gray level are implemented to extract and compare the shedding frequency of experiments and numerical predictions and cavitation evolution. It is concluded that the flow structure, shedding frequency and time-averaged characteristics are highly influenced by the dissolved air. Also, the numerical prediction will be more satisfactory when the modified turbulence models are applied.

Originality/value

To the best of the authors’ knowledge, the originality of this study is the modification of the turbulence model for better prediction of cavitating flow, and the validation of numerical results with corresponding experimental data.

中文翻译：

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修正湍流粘度对水翼周围三相云空化脱落动力学的评价——数值/实验分析

目的

本文旨在关注将溶解空气作为第三相考虑时Clark-Y水翼周围的空化流。针对RNG k-epsilon模型高估黏度导致预测效果不佳的问题，采用密度修正法、基于滤波器的模型和基于滤波器的密度修正模型等修正方法，对湍流模型进行了修正。此外，将数值结果与实验数据进行了比较。

设计/方法/途径

空化流被称为复杂的多相流，出现在局部压力低于饱和蒸汽压的区域。由于这种现象对涡轮机的腐蚀、振动、噪声、效率等有重大影响，许多研究已经对其进行分析。

发现

实验在配备 Clark-Y 水翼的矩形测试部分进行，提供空腔可视化、瞬时压力和振动波动。在有和没有溶解空气的情况下，针对不同的空化数进行模拟。应用快速傅立叶变换、连续小波变换和灰度级时空分布来提取和比较实验和数值预测和空化演化的脱落频率。得出的结论是，流动结构、脱落频率和时间平均特性受溶解空气的影响很大。此外，当应用改进的湍流模型时，数值预测将更令人满意。

原创性/价值

据作者所知，这项研究的独创性在于修改了湍流模型以更好地预测空化流，并用相应的实验数据验证了数值结果。