Dynamic reconfiguration of aquatic plants and its interrelations with upstream turbulence and drag forces

Abstract

This article explores the interrelations between flow, fluctuating drag forces, and dynamic reconfiguration experienced by four freshwater plant species in response to turbulent open-channel flow. The study is based on experiments conducted in a laboratory flume using single specimens of Ranunculus penicillatus, Fontinalis antipyretica, Myriophyllum alterniflorum, and Callitriche stagnalis. A significant correlation between drag fluctuations, plant movements, and upstream turbulence was found. The data also revealed that the plants in general exhibited spatial flapping-like motion, with the propagation velocity of perturbations along the plant being approximately constant and comparable to the upstream flow velocity. The analysis of statistical moments, spectra, cross-correlations, and coherence functions provided strong support to the conclusion that the dynamic reconfiguration directly affects the drag force exerted on the plants, in addition to the effect of the upstream turbulence.

Keywords:

• Aquatic vegetation
• drag
• dynamic reconfiguration of plants
• open-channel flow
• turbulence

Acknowledgements

The authors thank Dr Stuart Cameron for his help with the video processing, and the Associate Editor and three anonymous reviewers for providing their detailed and helpful comments. The research was partly supported by the Leverhulme Trust, grant F/00152/Z “Biophysics of flow–plant interactions in aquatic systems”, and was stimulated by the Scientific Research Network WO.027p11N.