Author(s): Runye Zhu; Yuexia Zhou
Linked Author(s):
Keywords: Hydrochory; Random Vortex Method; Maxey-Riley equation; Seed capture; Capillary force
Abstract: In river stems, vegetation significantly influences river morphology and floating seed captured by vegetation patch affects vegetation distribution. After being captured by vegetation patch, seeds have a chance to germinate and start the succession loop. Capillary force is a major mechanism contributing to seeds capture in vegetation patch. In this study, we focus on the capture probability of floating seeds by a single vegetation stem. Previous flume tests show the capture probability is related to flow velocity and seed characteristics. However, physical flume tests were time-consuming to gain the capture probability. To tackle this problem, we developed a one-way coupled numerical model including a flow field solver based on the Random Vortex Method (RVM) and a seed transport solver based on a modified Maxey-Riley equation accounting for the capillary force. In the simulation, the vegetation stem was represented by a single circular cylinder (with diameter), and seeds (with diameter) were released from the upstream side of the cylinder. Results showed that once seeds were captured, escape was difficult, aligning with previous flume findings. When the ratio, the calculated capture probability agreed well with the experiment and probability calculated from a semi-empirical formula. However, accuracy declined with smaller diameter ratios due to deviations from the Maxey-Riley equation’s assumption. Our results show that the Maxey-Riley equation can be applied to the seed capture problem. However, to build a more general framework that can model seed capture when is small, further research is needed.
Year: 2024