Study on Effects of Submerged Vegetation on Gravity Currents Dynamics

Abstract:

To study the movement characteristics of gravity currents propagated submerged vegetation, taking the vegetation in natural rivers as prototype, and front velocity of gravity currents represented velocity of gravity currents. The results showed that gravity currents propagated the short vegetation (length 30 cm, height 3 cm), it ridded on the top of vegetation and moved forward, and then contain the typical contour outflow the vegetation; presented a movement process that accelerated first, followed by uniform forward, then decreased , and finally slowed down. When gravity currents propagated the long vegetation (length 80 cm, height 6 cm), part of it was blocked behind the vegetation and only a part of gravity currents out of vegetation and moved forward, represented the process of first accelerating, then uniform velocity, then rapidly decelerating, and finally slow velocity. The movement process of gravity currents was divided into slumping phase and selfsimilar phase, and the blocking effect of vegetation can reduce the position of slumping phase translated into selfsimilar phase, and transform position was negatively related to the barrier effect of vegetation, but it was not related to the density of gravity currents. The vorticity values at the interface between gravity currents and environmental water was positive, and it was negative at the interface with horizontal bed. When the vegetation had a strong blocking effect, the mixing and entrainment effect was weak after gravity current propagated out of vegetation, and the outflow positively correlated with the density of gravity currents.