Laboratory observations of sand ripple evolution using bimodal grain size distributions under asymmetric oscillatory flows

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ABSTRACT Calantoni, J., Landry, B.J. and Penko, A.M., 2013. Laboratory observations of sand ripple evolution using bimodal grain size distributions under asymmetric oscillatory flows The heterogeneity of sand beds has been suggested to significantly impact the resulting sand ripple morphodynamics. However, the majority of previous experiments for sand ripple morphodynamics were conducted using only unimodal grain size distributions. Here we performed a series of ripple growth and transition experiments in a small oscillatory flow tunnel in the Sediment Dynamics Laboratory at the U.S. Naval Research Laboratory. Sand beds were constructed from mixtures of two unimodal sands median grain sizes of 0.30 mm (blue) and 0.70 mm (white), respectively. Experiments were performed with compositions of bimodal mixtures with percent by mass of 10/90, 25/75, 50/50, 75/25, 90/10. Additionally, similar experiments were performed for each of the unimodal cases (i.e., 100/0, 0/100). For each experiment, starting from a plan...