Experimental and theoretical study of wave–current turbulent boundary layers
Experimental and theoretical study of wave–current turbulent boundary layers
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DOI：
10.1017/jfm.2014.746
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发表时间：
2015-01
影响因子：
3.7
通讯作者：
Jing Yuan;O. Madsen
中科院分区：
文献类型：
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作者：
Jing Yuan;O. Madsen
摘要利用最先进的振荡水洞(OWT)产生流动和粒子图像测速系统对湍流波-流边界层流动进行了实验研究。在正弦波作用下的水流速度剖面显示了广泛使用的Grant-Madsen模型所提出的双对数剖面结构。然而，对于有非线性波存在的弱流，非线性波连续半周期内湍流的不对称性所产生的边界层流动污染甚至完全破坏了双对数剖面结构。为了解释实验结果，建立了一个半解析模型，该模型采用了一种严格的方法来解释时变湍流涡粘性。该模型可以准确地预测湍流不对称流动，从而成功地预测了非线性波浪试验中嵌入的平均速度和正弦或非线性波存在时的水流速度分布。由于波传播引起的Longuet-Higgins流在OWT流中不存在，也不包括在半解析模型中，因此有必要进一步扩展这一研究在沿海环境中的应用。
Abstract An experimental study of turbulent wave–current boundary layer flows is performed using a state-of-the-art oscillating water tunnel (OWT) for flow generation and a particle image velocimetry system for velocity measurements. The current velocity profiles in the presence of sinusoidal waves indicate a two-log-profile structure suggested by the widely-used Grant–Madsen model. However, for weak currents in the presence of nonlinear waves, the two-log-profile structure is contaminated or even totally obliterated by the boundary layer streaming which is produced by the asymmetry of turbulence in successive half-periods of nonlinear waves. To interpret experimental results, a semi-analytical model which adopts a rigorous way to account for a time-varying turbulent eddy viscosity is developed. The model can accurately predict turbulence asymmetry streaming, which leads to successful predictions of the mean velocity embedded in nonlinear-wave tests and the current velocity profiles in the presence of either sinusoidal or nonlinear waves. Since the Longuet-Higgins-type streaming due to wave propagation is absent in OWT flows and not included in the semi-analytical model, future work is necessary to extend this study for applications in the coastal environment.