The study reports an experimental investigation on the mechanism of the formation and development of isolated ripple zones over sand bed under unidirectional surface wave propagation. The ripple formation emerges due to the occurrence of vortices at the near-bed region under propagating wave fronts. A number of ripple patches are noticed after 100 cycles of the surface wave. To characterise these patches, Hilbert transform is used. These patches develop as a function of the number of wave cycles following Power law. Further, the rate of development of these patches increases with the increase of surface wave frequency as also reported in the literature. It is revealed that non-isolated turbulence singularity (random phase fractal signal) governs the erosion and deposition of sediment particles at the trough and crest of a progressive ripple front. The anti-phase behaviour of turbulence signal increases the wave excitation energy which may enhance the sediment erosion and transportation rate. However, it is hypothesized that the out-of-phase behaviour with moderate wave excitation energy contributes to the sediment deposition. Due to this, the frontal portion of the ripple does not attain a stable form and develops further.
Volume 131, 2022
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