3D Modal Solution for Tidally Induced Lagrangian Residual Velocity with Variations in Eddy Viscosity and Bathymetry in a Narrow Model Bay
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In this study, we examine the results obtained by the Finite-volume Coastal Ocean Circulation Model (FVCOM) regarding the effects of eddy viscosity and bathymetry on the three-dimensional (3D) Lagrangian residual velocity (LRV) in a narrow bay. The results are cast in terms of two nondimensional numbers: the ratio of friction to local acceleration (δ) and the ratio of the minimum depth over shoals to the maximum depth in the channel (ε). The ratio δ depends on the eddy viscosity and mean depth. For a given eddy viscosity, when ε > 0.5, the along-estuary LRV tends to be vertically sheared and when ε < 0.5, the exchange is laterally sheared. When ε << 1, the structure of the 3D, depth-integrated, and breadth-averaged LRV changes only slightly as δ increases. For ε values between 0.33 and 0.5, the structure of the 3D LRV is mainly laterally sheared. In the same ε range, the 3D and depth- integrated LRV exhibit reversed structures from high to low δ values. In addition, the breadth-averaged LRV weakens the typical twolayered circulation when δ decreases. When ε is 1, the two-layered vertical structure reverses direction, and a three- layered vertical structure develops in the outer bay as δ decreases.
Key wordseddy viscosity bathymetric effects Lagrangian residual velocity 3D narrow bay
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We express our sincere thanks to the developers of the FVCOM model. This study was supported by the National Natural Science Foundation of China (No. 41676003) and the National Natural Science Foundation of China–Shandong Joint Fund for Marine Science Research Centers (No. U1606402).
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