Model Description

The numerical model is an extended research version of Delft3D. Delft3D is a comprehensive numerical model suite, which includes a wave driver, hydrodynamic flow, sediment transport, and morphologic response modules ( The extensions to Delft-3D include a more sophisticated wave driver and sediment transport model to account for the effects of wave groupiness and corresponding infragravity waves on the near shore morphology (Reniers et al., 2000; Ad Reniers is presently a National Research Council Post-doctoral fellow at the Naval Postgraduate School under the direction of Prof. Thornton). The new wave and roller module, operating on the time scale of wave groups, are coupled to a depth-averaged flow model using the non-linear shallow water equations to predict the time dependent flow field. Sediment is stirred by the short-wave orbital motion and wave breaking induced turbulence, which is then transported by the mean and infragravity flow field. Divergences in the sediment transport pattern result in bed-level changes, which in turn affect the hydrodynamics. This is all done within the same time-step (as opposed to the modular set-up commonly used in Delft-3D). Typical wave periods associated with the infragravity waves are in the order of twenty seconds to a number of minutes. The spatial scales associated with the infragravity waves can be of the same order as the observed patterns present in the bathymetry (O(50) m and larger (Holman and Bowen, 1982), hence their potential importance in the near shore morphology.

Figure 1. The bathymetric evolution (changes with respect to the initial infinitely long, plane sloping beach in m) after approximately 12 days showing a barred beach (denoted by the dark blue) intersected by irregularly spaced rip-channels (qualitatively similar to field site conditions shown in Figure 1 of the ripex homepage). The average rip-spacing is in the order of 250 m. The arrows are mean current (averaged over sea-swell band) velocities showing rip currents.


Most recent update of this page: 23 December 2002 
Comments? Contact Web Page Administrator
Material contained herein is made available for the purpose of peer review and discussion and does not necessarily reflect the views of the Department of the Navy or the Department of Defense.

Privacy and Security Notice
External Links Notice