Experimental study on relation between scour and complex 3D flow field

In this paper, scour and flow fields around two spur dikes with different submergence ratios located in a 90 degrees developed bend were experimentally investigated. The spur dike and scour rate around the low submerged spur dike are higher than those around the high submerged condition. The ejection and sweep events are the predominant events in the upstream region of the spur dike. The larger peak of the power spectrum and the higher frequencies of sweep and ejection events in the low-submerged condition increase the scour rate at the early stages of the scour process. Interaction events are the main events in the downstream recirculation zone and may be the principal reasons for the sediment deposition process. The scour initiation region cannot be predicted using variance of the vertical velocity component. However, the estimation of the bed shear stress using the Reynolds stresses can predict the scour initiation region correctly. Strong relationships between the scour rate and triple correlations, quadrant analysis, turbulent kinetic energy flux, and power spectrum were found because the scour rate increases in the low submergence condition by the latter parameters increments. (C) 2017 Sharif University of Technology. All rights reserved.