Linear and nonlinear frequency-domain modelling of oscillatory flow over submerged canopies

IF 1.7 3区工程技术 Q3 ENGINEERING, CIVIL

Journal of Hydraulic Research Pub Date : 2023-09-03 DOI:10.1080/00221686.2023.2231433

Otto E. Neshamar, Niels G. Jacobsen, Dominic A. van der A, Tom O'Donoghue

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Abstract

An analytical and experimental study of flow velocities within submerged canopies of rigid cylinders under oscillatory flows is presented, providing insights into the momentum transfer mechanisms between the different flow harmonics. The experimental dataset covers an unprecedented wide range of flow amplitudes with in-canopy velocity reductions ranging between 0.2 and 0.8 of the free stream velocity (from inertia- to drag-dominated in-canopy flow). Results from the analytical model with nonlinear drag compare favourably to the experimental data. Having application of theories for free surface waves over canopies in mind, the effects of linearization of the drag are analysed by comparing sinusoidal and nonlinear model predictions. Finally, a unified prediction formula for in-canopy velocities for sinusoidal, velocity-skewed, and velocity-asymmetric free stream velocities is presented. The formula depends on two non-dimensional parameters related to inertia and drag forces, and the unified formula allows for easy assessment of the maximum in-canopy velocity.

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淹没树冠上振荡流动的线性和非线性频域建模

本文对振荡流动条件下刚性圆柱淹没冠内的流动速度进行了分析和实验研究，为不同流动谐波之间的动量传递机制提供了见解。实验数据集涵盖了前所未有的大范围流动幅度，冠层内流速降低幅度在自由流速度的0.2 - 0.8之间(从惯性到阻力主导的冠层内流动)。考虑非线性阻力的分析模型计算结果与实验数据吻合较好。考虑到树冠上自由表面波理论的应用，通过比较正弦模型和非线性模型预测，分析了阻力线性化的影响。最后，给出了正弦波、速度偏转和速度不对称自由流速度的冠层内速度统一预测公式。该公式依赖于与惯性和阻力有关的两个非维度参数，统一的公式可以方便地评估最大舱内速度。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Journal of Hydraulic Research 工程技术-工程：土木

CiteScore

4.90

自引率

4.30%

发文量

审稿时长

6.6 months

期刊介绍： The Journal of Hydraulic Research (JHR) is the flagship journal of the International Association for Hydro-Environment Engineering and Research (IAHR). It publishes research papers in theoretical, experimental and computational hydraulics and fluid mechanics, particularly relating to rivers, lakes, estuaries, coasts, constructed waterways, and some internal flows such as pipe flows. To reflect current tendencies in water research, outcomes of interdisciplinary hydro-environment studies with a strong fluid mechanical component are especially invited. Although the preference is given to the fundamental issues, the papers focusing on important unconventional or emerging applications of broad interest are also welcome.