Coherent Structures in Oscillating Turbulent Boundary Layers Over a Fixed Rippled Bed
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Coherent structures generated by oscillating turbulent boundary layers with or without a unidirectional current over a fixed, rippled bed are presented. The effect of ripple height and current intensity on the characteristics of these structures was investigated using a series of large-eddy simulations performed at Re α = 23,163. These flows are typical in coastal regions where complex wave-current interactions occur. A cartesian flow solver was used with the rippled bed represented using the immersed boundary (IMB) method. Results are presented for three ripple steepness values and two current magnitudes. Three different types of coherent structures were identified with their size, shape and evolution largely depending on ripple steepness, while, their potential effect on sediment transport is discussed.
KeywordsLES Oscillatory boundary layer Coherent structures Finite difference methods Immersed boundary method
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