Large-eddy Simulation of the Formation and Evolution of Benthic Ripples

摘要

Our primary objective is to simulate the ripple climate on the bed of the inner shelf at depths on the order of 20 m and over domains ranging from centimeters to kilometers in support of the Ripples DRI experiments and analyses. Our secondary objective is to use simulation to better understand the physics of ripple formation and sediment transport in this environment. In order to simulate the formation and evolution of benthic ripples, we employ a large-eddy simulation code with suspended sediment and moving-bed modules. The suspended-sediment module follows that of Zedler and Street (2001, 2006), and is incorporated into the parallel large-eddy simulation code PCUI (Cui and Street, 2001; 2004) in order to perform high-resolution simulations of sediment- ripple dynamics on parallel computers. We have employed several modifications to the implementation of Zedler and Street, most notably the implementation of the bottom boundary condition for sediment, which does not require knowledge of the near-bed turbulence parameterization. This is outlined in Chou and Fringer (2008a). Our moving bed module responds to the high-resolution shear stress imposed by the fluid at the bed and moves the bed position zb according to the formula (Gessler et al., 1999; Wu et al, 2000).