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Full-Text Articles in Engineering
Sediment Patterns From Fluid-Bed Interactions: A Direct Numerical Simulations Study On Fluvial Turbulent Flows, Nadim Zgheib, S. Balachandar
Sediment Patterns From Fluid-Bed Interactions: A Direct Numerical Simulations Study On Fluvial Turbulent Flows, Nadim Zgheib, S. Balachandar
Mechanical Engineering Faculty Publications and Presentations
We present results on the initial formation of ripples from an initially flattened erodible bed. We use direct numerical simulations (DNS) of turbulent open channel flow over a fixed sinusoidal bed coupled with hydrodynamic stability analysis. We use the direct forcing immersed boundary method to account for the presence of the sediment bed. The resolved flow provides the bed shear stress and consequently the sediment transport rate, which is needed in the stability analysis of the Exner equation. The approach is different from traditional linear stability analysis in the sense that the phase lag between the bed topology, and the …
Direct Numerical Simulation Of Transverse Ripples: 2. Self-Similarity, Bedform Coarsening, And Effect Of Neighboring Structures, Nadim Zgheib, J. J. Fedele, D. C. J. D. Hoyal, M. M. Perillo, S. Balachandar
Direct Numerical Simulation Of Transverse Ripples: 2. Self-Similarity, Bedform Coarsening, And Effect Of Neighboring Structures, Nadim Zgheib, J. J. Fedele, D. C. J. D. Hoyal, M. M. Perillo, S. Balachandar
Mechanical Engineering Faculty Publications and Presentations
Coupled bed-flow direct numerical simulations investigating the early stages of pattern formation and bedform (ripple) interactions were examined in a previous paper (Part 1), making use of the resolved flow field. In this paper (Part 2), we compare our results to published experimental data and provide an extensive quantitative analysis of the bed using spectral analysis and two-point correlations. The effect of the mobile rippled bed on the flow structure and turbulence is investigated locally (at specific streamwise locations) and over the entire computational domain. We show that developing ripples attain a self-similar profile in both the shape and the …
Direct Numerical Simulation Of Transverse Ripples: 1. Pattern Initiation And Bedform Interactions, Nadim Zgheib, J. J. Fedele, D. C. J. D. Hoyal, M. M. Perillo, S. Balachandar
Direct Numerical Simulation Of Transverse Ripples: 1. Pattern Initiation And Bedform Interactions, Nadim Zgheib, J. J. Fedele, D. C. J. D. Hoyal, M. M. Perillo, S. Balachandar
Mechanical Engineering Faculty Publications and Presentations
We present results of coupled direct numerical simulations between flow and a deformable bed in a horizontally periodic, turbulent open channel at a shear Reynolds number of Reτ = 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, …