奈特入口基台边界层分离与内波产生研究

K. Lamb
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引用次数: 45

摘要

本文报道了奈特湾海底分层潮流的数值模拟结果。采用非流体静力的二维模型,该模型通过使用垂直涡流粘度/扩散系数参数(仅在底部附近为非零),结合了无滑移的底部边界条件。在无粘模式运行中,快速形成较大的背风波,并迅速破裂,导致退潮初期形成高阻力状态和强下坡射流。无滑移底边界条件的使用导致边界层从基台顶部附近分离。这在气流发展的初始阶段显著降低了背风波的振幅。对于大多数模型运行,最终形成一个大的背风波,分离点沿着基岩的背风方向移动到背风波的下游位置。与非粘滞模型相比,过渡到这种高阻力状态的时间明显延迟。基台上方的分层减弱,底部上方的涡流粘度/扩散系数,以及基台下游(向海)一侧的致密水池,都有助于延迟过渡到高阻力状态,并可以完全消除这种状态。在一个使用底部上方垂直涡流粘度参数化的模型中,垂直扩散系数的降低消除了高阻力状态的形成。这表明,至少在某些情况下,夹带进入背风波会导致其增长,并导致形成高阻力状态。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
On boundary–layer separation and internal wave generation at the Knight Inlet sill
This paper reports results of numerical simulations of stratified tidal flow over the Knight Inlet sill. A non–hydrostatic, two–dimensional model is used, which incorporates a no–slip bottom boundary condition through the use of a vertical eddy viscosity/diffusivity parametrization that is non–zero only near the bottom. In inviscid model runs, a large lee wave is rapidly formed, which quickly breaks, leading to the formation of a high–drag state and a strong downslope jet in the early stages of the ebb tide. The use of a no–slip bottom boundary condition results in boundary–layer separation from near the top of the sill. This significantly reduces the amplitude of the lee wave during the initial stages of the flow development. For most model runs, a large lee wave is ultimately formed and the separation point moves down the lee of the sill to a position immediately downstream of the lee wave. The transition to this high–drag state is significantly delayed compared with inviscid model runs. Weakened stratification immediately above the sill, inclusion of an eddy viscosity/diffusivity above the bottom and a pool of dense water on the downstream (seaward) side of the sill can all contribute to a delay in the transition to a high–drag state, and can eliminate it entirely. For one model run using a vertical eddy viscosity parametrization above the bottom, a reduction of the vertical diffusivity eliminated the formation of a high–drag state. This suggests that at least in some cases entrainment into the lee wave can cause its growth and result in the formation of a high–drag state.
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期刊介绍: Proceedings A publishes articles across the chemical, computational, Earth, engineering, mathematical, and physical sciences. The articles published are high-quality, original, fundamental articles of interest to a wide range of scientists, and often have long citation half-lives. As well as established disciplines, we encourage emerging and interdisciplinary areas.
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