A determination of the frictional forces in a tidal current
A determination of the frictional forces in a tidal current
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DOI：
10.1098/rspa.1952.0175
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发表时间：
1952-09
期刊：
影响因子：
--
通讯作者：
K. F. Bowden;L. Fairbairn
中科院分区：
文献类型：
--
作者：
K. F. Bowden;L. Fairbairn
潮汐中的摩擦力是通过同时观测表面梯度和不同深度的水流而确定的。这些观测是在距离安格尔西岛红码头湾海岸几英里的地方进行的。这些梯度是由一对fafav型的公海潮汐计对海面高度的测量得出的，经过修改以提高精度。电流测量采用杜德森电记录电流计。每组观测延长超过24小时，并对它们进行半昼夜成分的谐波分析。这些分析的数据随后被用于动力学方程，给出底部摩擦力的振幅和相位，以及不同深度水中的内部剪切应力。获得了五套完整的记录，其中三套被认为给出了重要的结果。用F = kρU2表示底部摩擦力的振幅，其中U是从表面到底部的平均电流的振幅，ρ是水的密度，结果得到系数k的平均值为1⋅8 x 10─a。从表面到底部，发现水中的内摩擦应力随深度近似线性增加，并推导出相应的平均涡流粘度值。
The frictional forces in a tidal current have been determined from simultaneous observations of the surface gradients and the currents at various depths. The observations were made a few miles from the coast, off Red Wharf Bay, Anglesey. The gradients were derived from measurements of the surface elevations obtained by a pair of open-sea tide-gauges of the Favé type, modified to give increased accuracy. The Doodson electrically recording current meter was used for the current measurements. Each set of observations extended over 24 h, and they were subjected to harmonic analysis for the semi-diurnal constituent. The data from these analyses were then used in the dynamical equations, giving the amplitudes and phases of the frictional force at the bottom, and of the internal shearing stress in the water at various depths. Five complete sets of records were obtained, three of which are considered to have given significant results. Expressing the amplitude of the frictional force at the bottom in the form F ═ kρU2, where U is the amplitude of the mean current from surface to bottom, and ρ is the density of the water, the results give the coefficient k an average value of 1⋅8 x 10─a. The internal frictional stress in the water was found to increase approximately linearly with depth from the surface to the bottom, and the corresponding values of the mean eddy viscosity have been derived.