Impact flow and bed layering on equilibrium depth of scour at elliptical guide banks

Abstract

In the paper is present study the equilibrium scour at elliptical guide banks at different Fr number of the open flow, contraction, uniform or stratified bed model. A new approach for calculation equilibrium depth of scour at elliptical guide banks is elaborated and method for calculation equilibrium depth of scour bed at elliptical guide banks is presented. Analysis of the test, calculation and computer modelling results is made to estimate impact on relative equilibrium depth of scour: Fr number of the flow, local Froude number- FrVl, FrVequil, flow contraction, relative time, thickness and sequence of the bed layers. Relative equilibrium depth of scour is increasing with increase of Fr number of the open flow, local FrVl number, FrV equil at equilibrium depth of scour, relative time of scour, flow contraction and with different thickness and sequence of the bed layers. Calculation equilibrium depth of scour with the approach flow velocity and using the grain size only on the top of the bed or for the next layer calculate depth of scour with the same velocity, as it accepted nowadays, and neglecting changes of the flow parameters during the scour, bed layering can lead to wrong results and damages and losses.