REYNOLDS AVERAGED SIMULATION OF TURBID-DENSITY CURRENT

摘要

The deposition behavior of fine sediment is an important phenomenon, and yet is unclear to engineers concerned about reservoir sedimentation. Turbidity current with uniform velocity and concentration enters the channel via a sluice gate into a lighter ambient fluid and moves forward down-slope. During the last few years, the v~2 - f turbulence model has become increasingly popular due to its ability to account for near-wall damping without use of damping functions. In addition, it has been proved that the v~2 - f model to be superior to other RANS methods in many fluid flows where complex flow features is present. This model strongly can simulate the anisotropic behavior of flow especially near the wall region. Due to low Reynolds number turbulence of turbidity current, (its critical Reynolds no. is about 1000), and the nature of this current which like a wall jet, Eddy-viscosity concept cannot simulate this flow accurately. The accuracy of Reynolds averaged Navier-Stokes (RANS) turbulence models in predicting 2-D turbidity current is examined. In this work, a steady turbidity current is simulated by the ε - k , ε - k RNG, two-layer ε — k and modified v~2 - f model and all of these models are compared with experimental data. Results show that all the isotropic models produce a weak outcome on this current but with improving the ability of models the results become better. The deposition of particles and the effects of the concentration on their fall velocity are also investigated.