A Laboratory Study of Nonlinear Western Boundary Currents, with Application to the Gulf Stream Separation due to Inertial Overshooting*
A Laboratory Study of Nonlinear Western Boundary Currents, with Application to the Gulf Stream Separation due to Inertial Overshooting*
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非线性西边界流的实验室研究，应用于惯性超调引起的湾流分离*
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
I. Ellingsen
中科院分区：
文献类型：
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作者：
S. Pierini;P. Falco;G. Zambardino;T. McClimans;I. Ellingsen
在一个直径为5米的旋转水池中，通过物理模拟实验研究了非线性西边界流（WBCs）的各种动力学特征。活塞的运动与速度，可以低至5 0.5毫米秒21诱导一个水平的无剪切流的均匀的水，流过地形β斜率，经历向西强化。首先，白细胞的字符为各种程度的非线性进行了研究。通过向上变化，可以模拟从高度非线性惯性Charney状态到弱非线性状态的流动。在第一种情况下，依赖的纬向长度尺度上被认为是在协议与查尼的理论;对于较弱的流量，一个显着不同的功能依赖出现描述的初始过渡到线性，粘性的情况下。这提供了一个前所未有的覆盖范围的非线性白细胞依赖于振幅参数的实验数据。WBC分离的楔形大陆过去的海角（模拟哈特拉斯角），由于惯性过冲，然后进行了分析。通过增加流速，确定了一个关键的行为，根据这个行为，一个非常小的向上变化标志着从沿着海岸经过海角的WBC过渡到与海角分离而没有任何实质性偏转的WBC（几乎动态地类似于全尺寸的墨西哥湾流），就像墨西哥湾流延伸区一样。分析了大陆偏角的重要影响。最后，定性的影响倾斜的侧壁沿着直海岸被认为是：偏转的流远离西墙，由于保持位涡的趋势明显出现。
Various dynamical aspects of nonlinear western boundary currents (WBCs) have been investigated experimentally through physical modeling in a 5-m-diameter rotating basin. The motion of a piston with a velocity up that can be as low as up 5 0.5 mm s 21 induces a horizontally unsheared current of homogeneous water that, flowing over a topographic beta slope, experiences westward intensification. First, the character of WBCs for various degrees of nonlinearity is investigated. By varying up, flows ranging from the highly nonlinear inertial Charney regime down to a weakly nonlinear regime can be simulated. In the first case, the dependence of zonal length scales on up is found to be in agreement with Charney’s theory; for weaker flows, a markedly different functional dependence emerges describing the initial transition toward the linear, viscous case. This provides an unprecedented coverage of nonlinear WBC dependence on an amplitude parameter in terms of experimental data. WBC separation from a wedge-shaped continent past a cape (simulating Cape Hatteras) due to inertial overshooting is then analyzed. By increasing current speed, a critical behavior is identified according to which a very small change of up marks the transition from a WBC that follows the coast past the cape to a WBC (nearly dynamically similar to a full-scale Gulf Stream) that separates from the cape without any substantial deflection, as with the Gulf Stream Extension. The important effect of the deflection angle of the continent is analyzed as well. Finally, the qualitative effect of a sloping sidewall along a straight coast is considered: the deflection of the flow away from the western wall due to the tendency to preserve potential vorticity clearly emerges.