Bedform dynamics from coupled bed-flow direct numerical simulations
The project focuses on coupled direct numerical simulations between flow and a deformable bed in a horizontally periodic, turbulent open channel at a shear Reynolds number of 180. The feedback between the temporally and spatially evolving bed and the flow is enforced via the immersed boundary method. Using the near-bed flow field, we provide evidence on the role of locally intense near-bed vortical structures during the early stages of bed formation, from the emergence of quasi-streamwise streaks to the formation of incipient bedform crestlines. Additionally, we take a new look at a number of defect-related bedform interactions, including lateral linking, defect and bedform repulsion, merging, and defect creation, and show that the underlying mechanisms, in these flow-aligned interactions, are very similar to each other. Consequently, the interactions are labeled differently depending on the geometry of interacting structures and the outcome of the interaction.