Numerical study of turbulence and wave damping induced by vegetation canopies |
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| Institution: | 1. Department of Civil and Environmental Engineering, Old Dominion University, Norfolk, VA, USA;2. Center for Applied Coastal Research, University of Delaware, Newark, DE, USA;3. Department of Water Resources and Environmental Engineering, Tamkang University, Taipei, Taiwan;4. Department of Marine Engineering Technology, Texas A & M University, Galveston, TX, USA;1. Center for Applied Coastal Research, University of Delaware, Newark, DE, USA;2. Department of Civil and Environmental Engineering, Old Dominion University, Norfolk, VA, USA;1. Dept. of Hydraulic Eng., Delft University of Technology, Stevinweg 1, 2628 CN Delft, The Netherlands;2. Flanders Hydraulics Research, Berchemlei 115, 2140 Antwerp, Belgium |
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| Abstract: | Vegetation canopies control mean and turbulent flow structure as well as surface wave processes in coastal regions. A non-hydrostatic RANS model based on NHWAVE (Ma et al., 2012) is developed to study turbulent mixing, surface wave attenuation and nearshore circulation induced by vegetation. A nonlinear k ? ? model accounting for vegetation-induced turbulence production is implemented to study turbulent flow within the vegetation field. The model is calibrated and validated using experimental data from vegetated open channel flow, as well as nonbreaking and breaking random wave propagation in vegetation fields. It is found that the drag-related coefficients in the k ? ? model Cfk and Cf? can greatly affect turbulent flow structure, but seldom change the wave attenuation rate. The bulk drag coefficient CD is the major parameter controlling surface wave damping by vegetation canopies. Using the empirical formula of Mendez and Losada (2004), the present model provides accurate predictions of vegetation-induced wave energy dissipation. Wave propagation through a finite patch of vegetation in the surf zone is investigated as well. It is found that the presence of a finite patch of vegetation may generate strong pressure-driven nearshore currents, with an onshore mean flow in the unvegetated zone and an offshore return flow in the vegetated zone. |
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