Near wake of emergent vegetation patches in shallow flow

¹ Karlsruher Institut für Technologie, Institut für Hydromechanik, Kaiserstr.12, D-76131 Karlsruhe - Germany
² Institut de Mécanique des Fluides de Toulouse (IMFT), UMR 5502, 2 Allée du Professeur Camille Soula, F-31400 Toulouse - France
³ University of Hull, School of Environmental Sciences, HULL, HU6 7RX - Great Britain

^* e-mail: sina.wunder@kit.edu ^** e-mail: michele.trevisson@kit.edu ^*** e-mail: olivier.eiff@kit.edu

Abstract

Vegetation patches are particularly diffcult to quantify in terms of flow resistance due to their complex geometry and topological behaviour under hydrodynamic loading. They not only influence the water level and mean velocities due to the drag they exert, but they also affect the turbulence and hence all transfer processes such as the sediment transport dynamics in the surrounding area. Existing studies dealing with the interaction of flow and vegetation concern mostly measurements of the drag of single plants followed by analyses of the flow through and above homogeneous canopies. However, studies of the flow around single patches are uncommon and are mostly restricted to arrays of cylindrical elements. For leafy plants there is very limited information and understanding of how the flow evolves through and around the plants. This work aims at filling these gaps via complementary physical lab-scale and numerical experiments of the flow through and around an artificial vegetation patch. The experimental work focuses on PIV measurements in the wake of the patches whereas the method of large-eddy simulation is employed to provide additional insights of the flow inside the patch. Here we focus on results based on the PIV measurements.