On the threshold of motion of sediment grains: Turbulent fluctuation effects

Reza Barati, Seyed Ali Akbar Salehi Neyshabouri, Goodarz Ahmadi

Monday 29 june 2015

16:30 - 16:45h at Mississippi (level 1)

Themes: (T) Sediment management and morphodynamics, (ST) Sediment transport mechanisms and modelling

Parallel session: 3A. Sediment - Erosion

Particle movement will occur when the instantaneous fluid force on a particle is just larger than the instantaneous resisting force. One of the most important issues in this regard is the influence of turbulent fluctuation on threshold of motion. In this research, a series of numerical experiments was performed for studying the effects of turbulent fluctuation and turbulence structures on the initiation of sediment grains movement. A 3D Lagrangian numerical model was developed by considering various hydrodynamic forces such as non-linear drag force, the shear lift force, Magnus force, the buoyancy force, the added mass force, the history force and torque. The particle-particle interaction and particle-wall collision were included in the developed model using Discrete Element Method (DEM) and a random process, respectively. The fluid flow is described by 1D steady flow with 3D turbulent intensities. The verification of the model was implemented using different particle diameters and flow conditions. The results indicated that threshold of motion of sediment grains is strongly depends on stream-wise velocity fluctuations.