Reynolds stress modeling of vegetated open-channel flows

Abstract

The Reynolds stress model is applied to open-channel flows with vegetation. For the computation of pressure-strain term, the Speziale, Sarkar, and Gatski's model is employed. Mellor and Herring's model and Rotta's model are used for diffusion and dissipation rate of Reynolds stress, respectively. Flow structures of open-channels under two vegetative conditions are simulated, namely submerged and emergent plants. Plain open-channel flows are also simulated for comparisons. Computed profiles are compared with the results from the κ-ε model and the algebraic stress model as well as measured data available in the literature. For the plain open-channel flow and the open-channel flow with emergent vegetation, the Reynolds stress model is observed to simulate the non-isotropic nature of the flows better than the algebraic stress model and the κ-ε model. For the open-channel flow with submerged vegetation, it is found that the Reynolds stress model predicts the mean flow and turbulence quantities best compared with the other models. Sediment transport capacity of vegetated open-channel flows is also investigated by using the computed profiles. It is shown that the isotropic turbulence model underestimates the suspended load seriously.