Author(s): J. Gu; C. W. Li
Linked Author(s): Chi Wai Li
Keywords: Instantaneous discharge; Particle cloud; Initial dumping regime; Cross-flow; Buoyancy
Abstract: Artificial instantaneous discharge of dredged sediments in ambient waters is usually subjected to cross flow action. In shallow waters the initial discharge condition can be significant to the deposition pattern. The determination of the characteristics of this problem is thus important before environmental impact assessment can be made. In the present study, a series of laboratory experiments has been carefully conducted to investigate the transport and mixing of an isolated sand cloud in cross-flow. The results show that in the initial flow regime the effect of cross-flow and the associated turbulence on the cloud size is not important as compared to the effect of the unbalanced forces in the vertical direction including buoyancy due to the density difference between the sand cloud and the ambient flow, gravity as well as drag force on the particles. The transient variation of the vertical frontal position is close to that of a thermal in stagnant ambient water, which indicates that the frontal position is governed by the total buoyancy. The lateral width however displays a smaller value. This is probably due to that the cross-flow destroys the double vortices occurred in stagnant ambience, and the heavy particles are relatively unaffected by the ambient turbulence due to cross-trajectory effect.