Author(s): Zhengdao Tang; Lei Huang; Yan Liu
Linked Author(s): Lei Huang
Keywords: Relative submergence; Boulder arrays; Turbulent structures; Bed shear stress decomposition; Large eddy simulation
Abstract: This paper investigates the influence of relative submergence (defined as the ratio of water depth to the diameter of boulders, k=H/D) on turbulent structures and decomposition of the bed shear stress in flow through boulder arrays. The Large Eddy Simulation (LES) method is employed to simulate the flow through boulders arrays at the relative submergence ranging from k=0.25 to 3.50, with the water surface simulated by the level set method (LSM). It is found that the wake of boulders, characterized by a recirculation flow and funnel vortices downstream of boulders, only exits at k≥0.75 and is more prominent at higher k. Two types of coherent structures are identified in the wake, i.e., the flapping of boulder wakes with a wavelength of approximately 2D at low k and the meandering of secondary flow with a wavelength of 10D at high k. These two coherent structures Concerning the bed shear stress, a low bed shear stress region occurs upstream of boulders at low k while it shifts to the wake of boulders at high k, which is responsible for the different deposition patterns at different k observed in Papanicolaou et al., (2018). Based on the double-averaging concept, the bed shear stress is decomposed into the turbulent shear stress borne by mobile sediments (
Year: 2024