Flow behaviour around spur dyke founded in cohesive sediment mixtures

Abstract

This paper presents the results of flow and turbulence characteristics measured by a down-looking 16 MHz micro acoustic Doppler velocimeter around partially submerged spur dyke founded in a clay–gravel sediment mixture. Velocity and turbulence data were collected at various cross-sections at the wake and upstream sides of the spur dyke within and outside of the scour hole. The longitudinal velocity, turbulence intensities and Reynolds stresses were measured and quantitative analysis was carried out. Very small values of the longitudinal velocity component (negative) were obtained within the scour hole whereas larger values were obtained beyond the scour hole region. Turbulence intensities and Reynolds stresses were larger within the scour hole in the wake zone of the spur dyke. Bursting events, including outward interaction, ejection, inward interaction and sweep, were also analysed around the spur dyke. Quadrant analysis of the velocimeter data showed that the values of outward and inward interaction were higher within the scour hole around the spur dyke compared with the values of ejection and sweep events, while outside of the scour hole, the values of ejection and sweep events were higher than the values of outward and inward interaction events.