MEAN FLOW GENERATION ALONG A SLOPING REGION IN A ROTATING HOMOGENEOUSFLUID

Citation
Xz. Zhang et al., MEAN FLOW GENERATION ALONG A SLOPING REGION IN A ROTATING HOMOGENEOUSFLUID, J GEO RES-O, 101(C12), 1996, pp. 28597-28614
Citations number
27
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Oceanografhy
Journal title
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
ISSN journal
2169-9275 → ACNP
Volume
101
Issue
C12
Year of publication
1996
Pages
28597 - 28614
Database
ISI
SICI code
2169-9275(1996)101:C12<28597:MFGAAS>2.0.ZU;2-E
Abstract
The mean flow generated by an oscillatory (tidal) current normal to a long sloping region of constant cross section and finite height in a r otating homogeneous fluid is investigated analytically and by laborato ry experiments. The geometry is characterized by constant fluid depths h(s) and h(d) in the shallow (shelf) and deep regions, respectively, with the sloping region between being smooth and having a characterist ic width L. This physical system is characterized by the temporal Ross by number Ro(t) = omega/f, the Ekman number E, the geometric parameter s h(s)/h(d) and h(s)/L, and the normalized tidal excursion a(s)/L (or, alternatively, the Rossby number); here omega is the forcing frequenc y of the oscillatory current, f is the Coriolis parameter, and a(s) is the characteristic tidal excursion. The analysis assumes Ro(t) simila r to O(1), E much less than 1, h(s)/L much less than O(1), (h(d) - h(s ))/h(d) similar to O(1) (i.e., finite amplitude topography), and a(s)/ L similar to O(1) (i.e., finite amplitude tidal excursions). The analy sis is based upon a spectral method [Zimmerman, 1978] and predicts mea n flows along the depth contours of the topography with the shallow re gion on the right, facing downstream, for vertically upward, or northe rn hemisphere, rotation. The theoretical approaches used by other inve stigators using different frictional parameterizations for infinitesim al tidal excursions are also presented. The laboratory experiments wer e conducted in circular rotating test cells of 1.8 and 13.0 m diameter s in which continuous annular topographies of constant cross section w ere installed along the tank peripheries. The various theories were in qualitative support of the laboratory observations with respect to (1 ) mean flow direction, (2) location of most intense currents, and (3) dependence on the principal system parameters. Owing to the very small velocities associated with the mean flows generated and the inherent errors of the experiments, quantitative comparison could not be conclu sive. Predictions from the various theories give reasonable estimates of such quantities as mean Lagrangian displacements and Eulerian surfa ce transports.