Water waves in coastal areas are generally non- linear, exhibiting asymmetric velocity profiles with different amplitudes of crest and trough. The behaviors of the bound- ary layer under asymmetric waves are of great ...Water waves in coastal areas are generally non- linear, exhibiting asymmetric velocity profiles with different amplitudes of crest and trough. The behaviors of the bound- ary layer under asymmetric waves are of great significance for sediment transport in natural circumstances. While pre- vious studies have mainly focused on linear or symmetric waves, asymmetric wave-induced flows remain unclear, par- ticularly in the flow regime with high Reynolds numbers. Taking cnoidal wave as a typical example of asymmetric waves, we propose to use an infinite immersed plate oscillat- ing cnoidally in its own plane in quiescent water to simulate asymmetric wave boundary layer. A large eddy simulation approach with Smagorinsky subgrid model is adopted to investigate the flow characteristics of the boundary layer. It is verified that the model well reproduces experimental and theoretical results. Then a series of numerical experiments are carried out to study the boundary layer beneath cnoidal waves from laminar to fully developed turbulent regimes at high Reynolds numbers, larger than ever studied before. Results of velocity profile, wall shear stress, friction coeffi- cient, phase lead between velocity and wall shear stress, and the boundary layer thickness are obtained. The dependencies of these boundary layer properties on the asymmetric degree and Reynolds number are discussed in detail.展开更多
基金financial support to this work from the National Natural Science Foundation of China (Grants 11172307 and11232012)973 Program (2014CB046200)
文摘Water waves in coastal areas are generally non- linear, exhibiting asymmetric velocity profiles with different amplitudes of crest and trough. The behaviors of the bound- ary layer under asymmetric waves are of great significance for sediment transport in natural circumstances. While pre- vious studies have mainly focused on linear or symmetric waves, asymmetric wave-induced flows remain unclear, par- ticularly in the flow regime with high Reynolds numbers. Taking cnoidal wave as a typical example of asymmetric waves, we propose to use an infinite immersed plate oscillat- ing cnoidally in its own plane in quiescent water to simulate asymmetric wave boundary layer. A large eddy simulation approach with Smagorinsky subgrid model is adopted to investigate the flow characteristics of the boundary layer. It is verified that the model well reproduces experimental and theoretical results. Then a series of numerical experiments are carried out to study the boundary layer beneath cnoidal waves from laminar to fully developed turbulent regimes at high Reynolds numbers, larger than ever studied before. Results of velocity profile, wall shear stress, friction coeffi- cient, phase lead between velocity and wall shear stress, and the boundary layer thickness are obtained. The dependencies of these boundary layer properties on the asymmetric degree and Reynolds number are discussed in detail.
