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Wind Drag Coefficient in Large Shallow Lakes: Experimental Study and Modeling Application

Author(s): Lingwei Chen; Chen Zhang

Linked Author(s): Chen Zhang

Keywords: Wind drag coefficient; Surface wave; Physical experiment; Hydrodynamic model; Large shallow lake

Abstract: For large shallow lakes, wind stress is of particular significance in the hydrodynamic process, which affects lake water quality and ecosystem profoundly, and is imposed in the wind speed and the wind drag coefficient Cd terms in hydrodynamic models. Although many attempts have been made over oceans to describe the wind drag coefficient, there are few studies in the case of shallow lakes. Consequently, the Cd variability in shallow lakes due to unique wind and wave fields arises great concerns. In this study, a physical experiment was done to figure out the development of the drag coefficient in shallow water at light winds. A new drag coefficient expression was proposed based on the dimensional analysis and experimental results. The physical experiment obtained a minimum drag coefficient that was within the range reported in previous datasets at light winds. The expression we proposed indicated the importance of not only the wind but also the surface wave states in Cd variability. Furthermore, the hydrodynamic results of the shallow Upper Klamath Lake Model (UKLM) were validated by the new expression, compared with the traditional formula over oceans. The modified UKLM showed accurate flow velocities which were more consistent with site observations than that using the traditional formula. Thus, the new Cd expression that relies on wind and waves is recommended to predict the hydrodynamic process of large shallow lakes at light winds.


Year: 2023

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