Geometry‐induced residual eddies in estuaries with curved channels: Observations and modeling studies

Abstract

[1] Observations using a vessel-based acoustic Doppler current profiler conducted in two tidal channels with significant curvatures have shown persistent residual eddies. The residual eddies are clearly related to the bend of the channel. For a channel bending toward the north, the residual eddy on the east side of the channel tends to be clockwise, and the residual eddy on the west side of the channel tends to be counterclockwise. Water in these tidal channels is mostly well mixed or weakly stratified. Motivated by these observations, an analytic model is developed to study tidally induced mean circulation in a curved channel with arbitrary depth variations. A sinusoidal channel is used to simulate the effect of curved channels. A series of experiments with different parameters have shown consistently that a pair of residual eddies around the curvature exists. By analyzing the model results, it is found that advection is a major contributor to the residual eddies. Although the pressure gradient and the nonlinear wave propagation may not be negligible, especially for long channels, it is the advection that generates the vorticity of the residual eddies. The conclusion is true for both short and long channels. Here the division between a short and long channel is 0.6 of a quarter of the tidal wavelength. In addition, we also analyzed results from a finite volume numerical model for Lake Pontchartrain, which has curved tidal channels. The results demonstrate similar residual eddies as shown by the analytical model and the observations.

Effect of tropical cyclones on residual circulation and momentum balance in a subtropical estuary and inlet: Observation and simulation

“…Residual circulation can be created owing to physical characteristics of the estuary and inlet bathymetry [Kjerfve, 1978]. Li et al [2008] showed that curvature of the channel is responsible for the creation of residual flow for both short and long channels by increasing the advection significantly. In addition, the residual circulation could be created as a result of different forces like bottom friction [Winant, 2008], Coriolis [Valle-Levinson et al, 2003], density gradient [Fischer, 1976], nonlinear advection terms [Murty et al, 1980;Pingree and Maddock, 1977] and wind forcing [Janzen and Wong, 2002].…”

A Numerical Approach to Predict Water Levels in Ungauged Regions—Case Study of the Meghna River Estuary, Bangladesh

“…These nonlinear hydrodynamic phenomena were exposed due to spatial variation of riverbed resistance and the amplitude of semidiurnal tides. Earlier studies stated that tidally-driven river flow dynamics have relied on bed resistance and variable depth [50,51]. Inward flux was found to be high in the southern zones at those stations that are close to the bay and higher outward flux was found in the western channels and near the upstream regions.…”

Multi-scale modeling of Puget Sound using an unstructured-grid coastal ocean model: from tide flats to estuaries and coastal waters

“…The detailed theoretical aspects of the model are presented in Chen et al (2006). The model has been used to simulate the circulation and physical processes in estuaries, coastal waters, and open oceans Xue et al 2009;Li et al 2008;Huang et al 2008;Zhao et al 2006;Isobe and Beardsley 2006;Aoki and Isobe 2007;Weisberg and Zheng 2006a); wetting and drying processes in tide flats (Zheng et al 2003;Yang and Khangaonkar 2009); physical-biological interactions (Tian et al 2009;Ji et al 2008Ji et al , 2009Chen and Rawson 2005); storm surges (Weisberg and Zheng 2006b;Qi et al 2009); and nearshore restoration (Yang et al 2010a, b).…”