Ripple Morphodynamics in Oscillatory Flows

摘要

The long-term goal of our research is to improve our understanding of ripple morphodynamics in wave-current, boundary-layer flows. Our main focus is on the study of sediment transport in oscillatory boundary layers in the presence of unidirectional currents and the associated bed morphology (i.e. 2D and 3D ripples). We hope to improve currently available bed state prediction tools. To this end, both wave-induced and wave-current-induced oscillatory flow conditions are simulated in a Large Wave-Current Flume (LWCF) and in a Large Oscillating Water Sediment Tunnel (LOWST) built and equipped with an ONR DURIP Awards N00014-01-1-0540 and N00014-06-1- 0661. This effort studies the configuration of a uniform sand bed for a given regular oscillatory flow condition. In particular: the identification of dimensionless parameters controlling the transition between two and three dimensional ripples; the development of orbital, suborbital or anorbital ripples; and the occurrence of low steepness ripples. Attention is also directed to the hydro- and sediment dynamics of the flow over self formed ripple beds. The main objective is the development of a bedform predictor as a function of flow conditions and sediment characteristics.