- 498 - International Journal of Sediment Research, Vol. 26, No. 4, 2011, pp. 498–512 International Journal of Sediment Research 26 (2011) 498-512 A process-based model for sediment transport under various wave and current conditions Chi ZHANG 1 , Jin-Hai ZHENG 2 , Yi-Gang WANG 3 , Meng-Tao ZHANG 4 , Dong-Sheng JENG 5 , and Ji-Sheng ZHANG 6 Abstract The purpose of this study is to investigate the capability of a newly developed process-based model for sediment transport under a wide variety of wave and current conditions. The model is based on the first-order boundary layer equation and the sediment advection-diffusion equation. In particular, a modified low Reynolds number k-İ model is coupled to provide the turbulence closure. Detailed model verifications have been performed by simulating a number of laboratory experiments, covering a considerable range of hydrodynamic conditions such as sinusoidal waves, asymmetric waves and wave-current interactions. The model provides satisfactory numerical results which agree well with the measured results, including the time-averaged/dependent sediment concentration profiles and sediment flux profiles, as well as the time series of concentration at given elevations. The observed influences of wave orbital velocity amplitude, wave period and sediment grain size are correctly reproduced, indicating that the fundamental physical mechanisms of those processes are properly represented in the model. It is revealed that the present model is capable of predicting sediment transport under a wide range of wave and current conditions, and can be used to further study the morphodynamic processes in real coastal regions. Key Words: Sediment transport, Wave, Current, Numerical model 1 Introduction An essential task for coastal scientists and engineers is to develop reliable sediment transport models to simulate and predict nearshore morphodynamic behaviors under the influences of sea level rise, coastal structures, and other human activities (Yan et al., 2000; Zheng et al., 2002; Zhang et al., 2009). In most coastal regions, sediment transport is predominantly driven by short wave motion. A better understanding of wave-induced sediment transport is crucially important in coastal engineering. Intensive studies have been conducted in this field using both experimental and numerical approaches. Initial studies mainly focused on the sediment movement under sinusoidal waves. The relationship between sediment incipientation and wave bottom boundary layer was investigated (Komar and Miller, 1973; Madsen and Grant, 1976). Many empirical formulas for sediment transport have been proposed for a half wave cycle (Einstein, 1972; Nielsen, 1992). However, the simplified sinusoidal wave approach cannot describe all important mechanisms. When waves approach the coast, the wave shapes are 1 Dr., State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, 1 Xikang Road, Nanjing 210098, China, E-mail: czhang_hhu@hotmail.com 2 Prof., Corresponding author, State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, 1 Xikang Road, Nanjing 210098, China, E-mail: jhzheng@hhu.edu.cn 3 Prof., 4 Bachelor, 6 Assoc. Prof., College of Harbor, Coastal and Offshore Engineering, Hohai University, 1 Xikang Road, Nanjing 210098, China 5 Prof., Center for Marine Geotechnical Engineering Research, Shanghai Jiao Tong University, Shanghai 200240, China; Division of Civil Engineering, University of Dundee, Dundee DD1 4HN, United Kingdom Note: The original manuscript of this paper was received in Oct. 2010. The revised version was received in Oct. 2011. Discussion open until Dec. 2012.