Waves and currents over a fixed rippled bed: 3. Bottom and apparent roughness for spectral waves and currents
Waves and currents over a fixed rippled bed: 3. Bottom and apparent roughness for spectral waves and currents
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固定波纹床上的波浪和水流：3. 光谱波和水流的底部和表观粗糙度
DOI：
10.1029/1999jc900114
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发表时间：
1999
影响因子：
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通讯作者：
O. Madsen
中科院分区：
文献类型：
--
作者：
P. Mathisen;O. Madsen
本文是一系列的三个，介绍了实验的结果，旨在验证使用一个单一的底部粗糙度长度尺度的波浪和水流在粗糙的床。虽然前两篇论文集中在单色波和电流边界层流所经历的底部粗糙度，本文提出了额外的实验，调查使用的等效波表示扩展这些结果的频谱波和电流边界层流的结果。在一个20米长的波浪水槽中产生了由五个分量模拟的谱波和海流，水槽底部有固定的波纹。通过消除侧壁耗散和波-波相互作用的影响，从单个波分量的总衰减测量值确定由于底部摩擦引起的衰减。这些衰减估计用于建立代表性的摩擦系数，与现有的涡流粘度模型结合使用，以确定底部粗糙度。光谱波（在存在和不存在电流的情况下）所经历的底部粗糙度与单色波的底部粗糙度相匹配。当这些实验确定的底部粗糙度与涡流粘度模型结合使用时，对单个波分量的衰减预测与测量结果非常吻合。当波边界层厚度被定义为预测的速度赤字在波边界层的自由流速度的5%以内的高度时，在同向波的存在下，预测和测量的速度分布之间获得了极好的一致性。因此，这些实验表明，一个单一的底部粗糙度，当与一个等效的波表示，充分的特点是单色和光谱波流边界层流动在一个固定的波纹床。
This paper is the third in a series of three that presents the results of experiments designed to verify the use of a single bottom roughness length scale for waves and currents over a rough bed. While the first two papers concentrated on the bottom roughnesses experienced by monochromatic wave and current boundary layer flows, this paper presents the results of additional experiments that investigate the use of an equivalent wave representation to extend these results to spectral wave and current boundary layer flows. Spectral waves, simulated by five components, and currents were generated in a 20-m-long wave flume with a fixed rippled bottom. Attenuation due to bottom friction is determined from total attenuation measurements for individual wave components by removing the effects of sidewall dissipation and wave-wave interactions. These attenuation estimates are used to establish representative friction factors, which are used in conjunction with an existing eddy viscosity model to determine bottom roughnesses. The bottom roughnesses experienced by spectral waves (in the presence and absence of a current) match the bottom roughnesses for monochromatic waves. When these experimentally determined bottom roughnesses are used in conjunction with the eddy viscosity model, predictions of attenuation for individual wave components closely match measurements. When the wave boundary layer thickness is defined to be the height at which the predicted velocity deficit in the wave boundary layer is within 5% of the free stream velocity, excellent agreement is obtained between predicted and measured velocity profiles for currents in the presence of codirectional waves. Therefore these experiments show that a single bottom roughness, when used in conjunction with an equivalent wave representation, adequately characterizes both monochromatic and spectral wave-current boundary layer flows over a fixed rippled bed.
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