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首页> 外文期刊>Journal of Physical Oceanography >Measurements of Form and Frictional Drags over a Rough Topographic Bank
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Measurements of Form and Frictional Drags over a Rough Topographic Bank

机译：粗糙地形银行的形式和摩擦阻力的测量

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摘要

Pressure differences across topography generate a form drag that opposes the flow in the water column, and viscous and pressure forces acting on roughness elements of the topographic surface generate a frictional drag on the bottom. Form drag and bottom roughness lengths were estimated over the East Flower Garden Bank (EFGB) in the Gulf of Mexico by combining an array of bottom pressure measurements and profiles of velocity and turbulent kinetic dissipation rates. The EFGB is a coral bank about 6 km wide and 10 km long located at the shelf edge that rises from 100-m water depth to about 18 m below the sea surface. The average frictional drag coefficient over the entire bank was estimated as 0.006 using roughness lengths that ranged from 0.001 cm for relatively smooth portions of the bank to 1-10 cm for very rough portions over the corals. The measured form drag over the bank showed multiple time-scale variability. Diurnal tides and low-frequency motions with periods ranging from 4 to 17 days generated form drags of about 2000 N m(-1) with average drag coefficients ranging between 0.03 and 0.22, which are a factor of 5-35 times larger than the average frictional drag coefficient. Both linear wave and quadratic drag laws have similarities with the observed form drag. The form drag is an important flow retardation mechanism even in the presence of the large frictional drag associated with coral reefs and requires parameterization.
机译：跨地形的压差会产生与水柱中的水流相反的形式阻力，作用在地形表面粗糙度元素上的粘性和压力会在底部产生摩擦阻力。通过结合一系列底部压力测量值以及速度和湍流动力学耗散率的分布图，估算了墨西哥湾东花卉园岸（EFGB）的形状阻力和底部粗糙度长度。 EFGB是一个位于岸边的宽约6公里，长10公里的珊瑚堤，从水深100米上升到海面以下约18 m。使用粗糙度长度，整个堤岸的平均摩擦阻力系数估计为0.006，范围从堤岸相对光滑部分的0.001厘米到珊瑚上非常粗糙部分的1-10厘米不等。银行上的测量形式拖曳显示出多个时标变化。周期为4至17天的日潮和低频运动形成约2000 N m（-1）的阻力，平均阻力系数在0.03至0.22之间，是平均水平的5-35倍摩擦阻力系数。线性波动和二次阻力定律都与观测到的形式阻力相似。即使在存在与珊瑚礁相关的大摩擦阻力的情况下，阻力形式也是重要的阻滞机理，并且需要进行参数设置。

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