Impact of turbulence and secondary flow on the water surface in partially filled pipes
Impact of turbulence and secondary flow on the water surface in partially filled pipes
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DOI：
10.1063/5.0078564
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发表时间：
2022-03
影响因子：
4.6
通讯作者：
Yan Liu;T. Stoesser;H. Fang
中科院分区：
文献类型：
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作者：
Yan Liu;T. Stoesser;H. Fang
对不同填充度下的非完全填充管道内的湍流流动进行了大涡模拟（LES），研究了水面对湍流及其下二次流的响应，并利用实验和直接数值模拟数据对LES进行了验证。随着水深的增加，水面波动的幅度随着主二次流强度的增加而增加。瞬时水面和湍流下面的可视化显示，薄表面波产生的流动在较浅的情况下，而在较深的情况下，表面波的垂直速度波动的影响。水面波动h′的预乘谱进一步证明了表面波的起源。在浅流中，h′谱的峰值频率与u′谱和v′谱的峰值频率一致，而在深流中，h ′谱的峰值频率与w′谱的峰值频率更一致。此外，表面波的输运模式进行了研究的波数-频率谱。在波数-频率谱中观察到三种类型的表面波，即，(1)相速度等于表面速度的对流波，（2）无旋色散重力-毛细波，和（3）由二次流引起的驻波。
Large eddy simulations (LESs) of turbulent flow in partially filled pipes at various filling degrees are conducted to investigate the response of the water surface to the turbulence and the secondary flow below it. LESs are validated first using experimental and direct numerical simulation data. At increasing water depth, the magnitude of water surface fluctuations increases with increasing strength of the main secondary flow. Visualizations of the instantaneous water surface and the turbulent flow underneath reveal that thin surface waves are generated by flow meandering in the shallower case, whereas surface waves in the deeper cases are influenced by the vertical velocity fluctuation. Pre-multiplied spectra of the water surface fluctuation, h′, provide further evidence of the origin of the surface waves. In the shallow flow, the peak frequency of the h′ spectra is consistent with the peak frequency of the u′ and v′ spectra, while for deeper flows, it agrees more with the w′ spectra. Furthermore, the transport patterns of the surface waves are investigated by the wavenumber-frequency spectra. Three types of surface waves are observed in the wavenumber-frequency spectra, i.e., (1) convective waves with phase velocity equaling the surface velocity, (2) irrotational dispersive gravity-capillary waves, and (3) stationary waves caused by secondary currents.