Numerical Simulation Of Sedimentation And Circulation In Rectangular Marina Basins

Shear-induced circulation and sedimentation of cohesive particles in rectangular marina basins are simulated using finite difference and finite element techniques, respectively. The solutions consider the effects of varying basin length, basin width, entrance width, entrance placement, number of entrances, suspended sediment concentration at the entrance, entrance boundary velocity, and strength of transverse dispersion. The results are presented in graphical form to facilitate the estimation of basin-averaged velocities and sedimentation rates for a variety of simple marina configurations. Slotta and Nobel's (1977) basin-flushing guidelines are recommended for use jointly with these results to warn of undesirable flushing characteristics. The shear-driven vortex circulation may be enhanced by increasing the relative entrance width or decreasing either the basin width or length. Sedimentation varies directly with the entrance width, the concentration of suspended sediment at the entrance boundary, and the strength of transverse dispersion. It varies inversely with the entrance boundary velocity, basin length, and basin width. A square plan view with a single entrance, centrally located in the breakwater, produces both maximum basin-averaged circulation and maximum sedimentation. An optimum balance beween basin area, circulation, and sedimentation should be achieved through increasing the basin length rather than width. Basins with length/width ratios greater than unity and an entrance located downstream of the center of the breakwater will have lower sedimentation rates than an upstream entrance; an upstream entrance is preferable for basins with lower aspect ratios. For a given total entrance width, multiple entrances can be used to measurably improve the velocity distribution without significantly increasing the basin-averaged sedimentation rates. Grant no. 04-7-158-44085