Author(s): Qian-Lu Xiao; Qing Feng
Linked Author(s):
Keywords: No keywords
Abstract: The flow field structure of the wave-current interaction is one of the essential issues for estuarine and coastal hydrodynamics, which is directly related to the nearshore pollutant transport, nutrient transport and biophysical processes. Based on the vertical two-dimensional Navier-Stokes equation, the theoretical study is carried out with the velocity decomposition method and the momentum flux caused by the wave motion is fully considered. The Airy wave theory is adopted to simplify the corresponding formula in the governing equation of velocity profile. According to the general theory of dielectric wave, the wave-induced multi-source oscillatory energy propagation mode is established, which explains in essence the influence of water particle oscillatory under wave-surface on the vertical turbulent structure. This mode is applied in the deduction of the momentum transfer coefficient considering the influence of the water particle oscillatory and the flow turbulence induced by the bed shear stress based on the Prandtl mixing theory. A new analytic formula of velocity profile under wave-current is derived, which is composed of Logarithmic function and Rayleigh distribution function. By comparison of the experimental results, the predicted values of the deduced formulas are in good agreement with the measured values, indicating that deduced formulas could response the effects of wave dynamics and momentum transfer coefficient on the velocity profile for waves following and opposing currents. Also, our formula is practical compared to other wave- current models. Furthermore, the formula could also be appropriate to characterize the flow velocity distribution in the rigid submerged vegetation zone under combined wave and current flows. The presence of the canopy can significantly reduce the mean flow velocity and result in a uniform profile in the height of the plant stems, and a distinctive shear layer exists near the canopy top in pure current and current with following wave. This study could help to implement increasingly accurate evaluation for the nearshore dynamic environment and provide theoretical basis for the forcing mechanism of wave-current interaction on aquatic ecosystems.
Year: 2022