In this paper the results of theoretical studies on suspendeds and transport under irregular waves in the ripple regime are presented. The results from the lDV model, which simulates the instantaneous velocity and sand concentration from close to the bed up to higher in the water column are obtained. | Vietnam Journal of Mechanics, NOST of Vietnam Vol. 22, 2000, No 2 (71 - 86) lDV MODEL FOR SUSPENDED SAND TRANSPORT UNDER WAVES IN RIPPLE REGIME DANG Huu CHUNG Institute of Mechanics, NCST of Vietnam ABSTRACT. In this paper the results of theoretical studies on suspended sand transport under irregular waves in the ripple regime are presented. The results from the lDV model, which simulates the instantaneous velocity and sand concentration from close to the bed up to higher in the water column are obtained. The model is based on the classical diffusion approach taking both the turbulence-related and the effective waverelated diffusion into account . It shows that the time-averaged sand concentrations can be simulated reasonably well in the ripple regime using calibrated equations . Especially, the proposed formula for the diffusion coefficient by wave, considerably improved the behaviour of vertical distribution of suspended sediment concentration. Finally, the waverelated suspended sediment transport in depth-integration is computed and compared with the measured data. The accuracy of the suspended transport was found to be strongly dependent on using measured data or predictive formula for concentration at the bed boundary. 1. Introduction The phenomenon o{ sediment transport is a complicated natural proces;:; and so far it has not been comprehensively understood. This problem attracts attentions of many researchers with different solutions of both mathematical and I physical models to achieve a better understanding of this process. The suspended sand rt rate in the coastal zone comprises two major components: the current-related transport component and the wave-related one. The current-related transport component is considered to be the convective sand transport carried by the mean currents such as tide, wind and wave-driven currents in the presence of short (high-frequency) surface waves acting as stirring agents. The wave-related sand is
