The Influence of Three?Dimensional Topography on Turbulent Flow Structures Over Dunes in Unidirectional Flows

Dunes are the most prevalent bedform present in sand-bedded rivers and their morphology typically comprises multiple scales of three-dimensional topography. However, our understanding flow over dunes is predicated largely on two-dimensional models, a condition which rare nature. Here, we results Large Eddy Simulations static, dune field, using two- three- dimensional topographic realisation, to investigate interaction between bed topography turbulent structures. We show that bedforms increases velocity stoss slope reduces size leeside separation zone as compared 3D Flow generates twice many vortices bedforms, these longer, wider taller than counterparts. Turbulence dominated by hairpin-shaped Kelvin-Helmholtz instabilities interact with brink point region crest down lee slope, generate high shear stresses for long durations. These used propose new conceptual model showing differences bedforms. The findings highlight how size, stacking coherent structures into larger superstructures may be critical sediment entrainment, dictate relationship event duration magnitude drives impulses at bed. This will ultimately lead an increased three-dimensionality morphology.