Large eddy simulation and direct numerical simulation of a fixed spherical particle on a wall in a turbulent open channel flow

Large Eddy Simulation (LES) and Direct Numerical Simulation (DNS) of open channel flow over a stationary particle has been performed at a Reynolds number of Re-tau = 498. Different from modelling the sediment transport this study concentrates on an individual particle and investigates the interaction between turbulence coherent structure, with special emphasis given to the characterisation of the drag and lift forces acting on a particle. LES and DNS using immersed boundary method were performed to examine the characteristics of hydrodynamic forces acting on a particle due to turbulent flow whilst stationary on a wall. Numerical results found the presence of a single particle stationary on a wall modified the mean velocity profile and turbulence quantities in the vicinity of the particle. The intensity of the particle force fluctuations change as the size of the particle increases or decreases furthermore, the effect of the wall is strongest when the particle is in contact. The instantaneous and mean velocity predictions around the sphere provide a reasonably accurate prediction of the mean drag obtained from the both simulations. The velocity flow field around the particle is in agreement with experimental data, which has been used to validate the results. Additionally, we present here the instantaneous numerical results on the particle and surrounding turbulent flow, which provide a strong correlation between particle entrainment and turbulent structures.