Abstract
Physical modelling of vegetated flows is an essential component of process-based investigations into vegetation
ecohydraulics. The vast majority of research into vegetated flows has employed rigid model vegetation, so that
the canopy’s geometry (i.e. its height and frontal area) is invariant and easy to quantify. Here, we demonstrate
that embedding realism (in the form of flexibility and buoyancy) in the model vegetation can have a profound
impact on the hydrodynamics. Specifically, we compare rates of vertical mixing in two types of model canopy
(with identical heights and frontal areas) subjected to oscillatory flow over a range of realistic wave heights and
periods. The two types of canopy were: (1) a rigid canopy consisting of wooden dowels, and (2) an array of
flexible, buoyant model plants designed to mimic a meadow of the seagrass Posidonia australis. Dynamic
similarity between the model and real seagrass was achieved by matching the two dimensionless ratios of the
dominant forces that govern plant motion (rigidity, buoyancy and drag). Results demonstrate a significant
difference in flow structure between the two canopies and a significant reduction in the rate of vertical mixing in
a flexible canopy, relative to the rigid analogue. Thus, while the use of dynamically-scaled vegetation models
adds a layer of modelling complexity, it represents a step towards a more faithful recreation of flow and mixing
in these systems.
ecohydraulics. The vast majority of research into vegetated flows has employed rigid model vegetation, so that
the canopy’s geometry (i.e. its height and frontal area) is invariant and easy to quantify. Here, we demonstrate
that embedding realism (in the form of flexibility and buoyancy) in the model vegetation can have a profound
impact on the hydrodynamics. Specifically, we compare rates of vertical mixing in two types of model canopy
(with identical heights and frontal areas) subjected to oscillatory flow over a range of realistic wave heights and
periods. The two types of canopy were: (1) a rigid canopy consisting of wooden dowels, and (2) an array of
flexible, buoyant model plants designed to mimic a meadow of the seagrass Posidonia australis. Dynamic
similarity between the model and real seagrass was achieved by matching the two dimensionless ratios of the
dominant forces that govern plant motion (rigidity, buoyancy and drag). Results demonstrate a significant
difference in flow structure between the two canopies and a significant reduction in the rate of vertical mixing in
a flexible canopy, relative to the rigid analogue. Thus, while the use of dynamically-scaled vegetation models
adds a layer of modelling complexity, it represents a step towards a more faithful recreation of flow and mixing
in these systems.
Original language | English |
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Title of host publication | Proceedings of the 11th International Symposium on Ecohydraulics |
Editors | J.A. Webb, J.F. Costelloe , R. Casas-Mulet, J.P. Lyon , M. Stewardson |
Place of Publication | Melbourne, Australia |
Publisher | Engineers Australia |
ISBN (Print) | 9780734053398 |
Publication status | Published - 2016 |
Event | 11th International Symposium on Ecohydraulics - Melbourne, Australia, Melbourne, Australia Duration: 7 Feb 2016 → 12 Feb 2016 |
Conference
Conference | 11th International Symposium on Ecohydraulics |
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Country/Territory | Australia |
City | Melbourne |
Period | 7/02/16 → 12/02/16 |