Abstract
This study examines the turbulence in wall-wake flow downstream of an isolated dunal bedform. The streamwise flow velocity and Reynolds shear stress profiles at the upstream and various streamwise distances downstream of the dune were obtained. The results reveal that in the wall-wake flow, the third-order moments change their signs below the dune crest, whereas their signs remain unaltered above the crest. The near-wake flow is featured by sweep events, whereas the far-wake flow is controlled by the ejection events. Downstream of the dune, the turbulent kinetic energy production and dissipation rates, in the near-bed flow zone, are positive. However, they reduce as the vertical distance increases up to the lower-half of the dune height and beyond that, they increase with an increase in vertical distance, attaining their peaks at the crest. The turbulent kinetic energy diffusion and pressure energy diffusion rates, in the near-bed flow zone, are negative, whereas they attain their positive peaks at the crest. The anisotropy invariant maps indicate that the data plots in the wall-wake flow form a looping trend. Below the crest, the turbulence has an affinity to a two-dimensional isotropy, whereas above the crest, the anisotropy tends to reduce to a quasi-three-dimensional isotropy.
Highlights
Turbulent flow over dunal bedforms fascinates researchers
This study puts into focus the turbulence in wall-wake flow downstream of an isolated dunal
This The study puts into focus the turbulence wall-wake flow of flow an isolated dunal bedform
Summary
Turbulent flow over dunal bedforms fascinates researchers. The topic is important from the viewpoint of intrinsic scientific reasons, and owing to its far-reaching applications in engineering. A 5 cm down-looking Vecrtino probe (acoustic Doppler velocimetry), called Vectrino plus, In a natural streamflow, an isolated dunal bedform acts as a bluff-body, producing wall-wake was used to capture the instantaneous three-dimensional flow velocity components along the flume flow at its downstream. The wall-wake flow downstream of an isolated dunal bedform in an approach wall-shear flow, being in (x, y, z) before and after decontaminating the data in Run 1, respectively, at a relative streamwise different from a free-wake flow, is rather intricate. The Sdf (kw ) curves of decontaminated shedding downstream of bed-mounted bluff-bodies in both near- and far-wake flows were studied signals compare well with Kolmogorov ‘–5/3’ scaling law in the inertial subrange for kw ≥ 30 rad s−1. This study puts into focus the flow and turbulence characteristics downstream of an isolated two-dimensional dunal bedform over a rough bed in order to advance the present state-of-the-art.
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