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Numerical and experimental investigation of flow and scour around a circular pile
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2005
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The study numerically and experimentally investigates flow around a vertical circular pile in a steady current. A three‑dimensional numerical model, validated with laser‑Doppler anemometry and hot‑film shear‑stress data, is coupled to a morphologic model that includes bed‑load transport and sand‑slide mechanics to predict scour around the pile. The simulation reproduces the main scour features, matching upstream equilibrium scour depth with experiments while showing up to 30 % discrepancy downstream, and indicates that bed‑shear‑stress amplification is markedly reduced in equilibrium compared to the initial flat bed.
The flow around a vertical circular pile exposed to a steady current is studied numerically and experimentally. The numerical model is a three-dimensional model. The model validation was achieved against new experimental data (which include two-component laser-Doppler anemometry (LDA) flow measurements and the hot-film bed shear stress measurements, and reported in the present paper) and the data of others, and a The amplification of the bed shear stress around the pile (including the areas under the horseshoe vortex and the lee-wake region) was obtained for various values of the previously mentioned parameters. The steady-state flow model was coupled with a morphologic model to calculate scour around a vertical circular pile exposed to a steady current in the case of non-cohesive sediment. The morphologic model includes (i) a two-dimensional bed load sediment-transport description, and (ii) a description of surface-layer sand slides for bed slopes exceeding the angle of repose. The results show that the present numerical simulation captures all the main features of the scour process. The equilibrium scour depth obtained from the simulation agrees well with the experiments for the upstream scour hole. Some discrepancy (up to 30%) was observed, however, for the downstream scour hole. The calculations show that the amplification of the bed shear stress around the pile in the equilibrium state of the scour process is reduced considerably with respect to that experienced at the initial stage where the bed is plane.