Reynolds Stress Modelling Of Open Channel Flow With Suspended Vegetation

Theoharris Koftis, Panayotis Prinos

Thursday 2 july 2015

15:20 - 15:35h at Amazon (level 1)

Themes: (T) Water engineering, (ST) River and coastal engineering

Parallel session: 12B. Engineering - River

Suspended vegetation refers to aquatic canopies that are found in the free surface and extend down forming a gap between the canopy and the bed. Such canopies are commonly found in aquaculture, mussel culture for instance and in ponds where exotic species of suspended vegetation (e.g. Eichhornia crassipes, Pistia stratiotes and Salvinia molesta) cover the water surface. In this work the effect of suspended vegetation on open channel flow is studied numerically. The VARANS (Volume-Averaged-Reynolds-Averaged-Navier-Stokes) equations are solved numerically in conjunction with the Reynolds Stress Model (RSM) of Ayotte et al. (1999) turbulence model modified by Souliotis and Prinos (2011). The effect of the vegetation density, defined by the parameter _ as the frontal area per unit volume, on the mean velocities and turbulence characteristics is investigated by varying the vegetation density from 1.272 to 0.477. Also the effect of the relative gap (height of the gap hg beneath the canopy over the total flow depth H) is studied with values of hg/H varying from 0.125 to 0.5. Numerical results are compared with experimental measurements of Plew (2011). Mean velocities and shear stresses are found in good agreement for all cases. Discrepancies found between numerical and experimental normal stresses are discussed.