Improved Numerical Computing Method for the 3D Tidally Induced Lagrangian Residual Current and Its Application in a Model Bay with a Longitudinal Topography
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An improved method for computing the three-dimensional (3D) first-order Lagrangian residual velocity (uL) is established. The method computes tidal body force using the harmonic constants of the zeroth-order tidal current. Compared with using the tidal-averaging method to compute the tidal body force, the proposed method filters out the clutter other than the single-frequency tidal input from the open boundary and obtains uL that is more consistent with the analytic solution. Based on the new method, uL is calculated for a wide bay with a longitudinal topography. The strength and pattern of uL are mostly determined by the parts of the tidal body force related to the vertical mixing of the Stokes’ drift and the Coriolis effect, with a minor contribution from the advection effect. The geometrical shape of the bay can influence uL through the topographic gradient. The magnitude of uL increases with the increases in tidal energy input and vertical eddy viscosity and decreases in terms of the bottom friction coefficient.
Key wordsLagrangian residual current tidal body force numerical method dynamics
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This study was supported by the National Natural Science Foundation of China (No. 41676003) and the NSFC Shandong Joint Fund for Marine Science Research Centers (No. U1606402).
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