Blade dynamics in combined waves and current
Blade dynamics in combined waves and current
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DOI：
10.1016/j.jfluidstructs.2019.03.020
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发表时间：
2019-05-01
影响因子：
3.6
通讯作者：
Nepf, Heidi
中科院分区：
文献类型：
--
作者：
Lei, Jiarui;Nepf, Heidi
沉水植物（SAV），如海草，是灵活的，并重新配置（弯曲），以响应波浪和电流。叶片运动和重新配置修改流体动力阻力。修改后的阻力可以通过有效叶片长度l（e）来描述，其被定义为导致与长度为l的柔性叶片相同的阻力的刚性叶片的长度。在许多自然环境中，SAV暴露于波浪和电流的组合。本研究推导并使用实验室测量结果，以验证基于柯西数的波浪和水流组合的有效叶片长度的新预测，柯西数描述了由于叶片刚度引起的水动力阻力与恢复力的比率。使用暴露于周期为2 s的波浪以及波速（U-w）和流速（U-C）范围内的叶片的力测量值和数字图像来估计有效叶片长度。测量结果还用于验证叶片运动的数值模拟。一旦验证，模拟被用来扩大研究的参数空间，以更广泛的波条件，特别是较长的波周期。当U-C < 1/4U（w）时，叶片运动和水动力阻力以波动为主。当U-C > 2U（w）时，叶片运动和水动力阻力主要由水流控制。(C)2019爱思唯尔有限公司版权所有。
Submerged aquatic vegetation (SAV), such as seagrass, is flexible and reconfigures (bends) in response to waves and current. The blade motion and reconfiguration modify the hydrodynamic drag. The modified drag can be described by an effective blade length, l(e), which is defined as the length of a rigid blade that results in the same drag as a flexible blade of length l. In many natural settings SAV is exposed to combinations of waves and current. This study derived and used laboratory measurements to validate new predictions of effective blade length for combined waves and current based on a Cauchy number, which describes the ratio of hydrodynamic drag to the restoring force due to rigidity of blade. Force measurements on and digital images of blades exposed to waves with a 2-s period and with a range of wave velocity (U-w) and current speed (U-C) were used to estimate the effective blade length. The measurements were also used to validate a numerical simulation of blade motion. Once validated, the simulation was used to expand the investigated parameter space to a wider range of wave conditions, and in particular longer wave periods. Forth U-C < 1/4U(w), the blade motion and hydrodynamic drag were wave-dominated. For U-C > 2U(w) the blade motion and hydrodynamic drag were current-dominated. (C) 2019 Elsevier Ltd. All rights reserved.