Numerical and experimental modelling of dam break interaction with a sediment bed

McMullin, Nicholas (2015) Numerical and experimental modelling of dam break interaction with a sediment bed. PhD thesis, University of Nottingham.

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A dam break event is considered, taking place over a uniform sediment bed. Understanding and modelling the erosion that occurs when the fluid behind the dam collapses at release has important applications in coastline morphodynamics / beach erosion modelling.

A new coupled two dimensional Navier-Stokes solver and sediment transport model is presented with novel methods for dealing with non-converging solutions to the Navier-Stokes equations and a new adaptation to the Youngs [1982] volume-of-fluid reconstruction scheme. The implementation of a sediment transport model includes a new method for accounting for mass conservation for the transition of sediment between bed and flow as well as a novel method for accounting for the redistribution of material associated with the maintenance of the critical angle of repose or slope limit. The model is validated and then applied to a dam break simulation for various backwater and tailwater conditions.

Classical experimental realizations of dam break events have involved the rapid removal of a barrier in a flume [e.g. [Levin, 1952; Dressler, 1954; Bell et al., 1992])]. However, early-time flow analysis encounters two problems with this method. Firstly, the removal of the barrier creates a strong vortex sheet on the face of the static fluid immediately behind the barrier that is not present in either the idealized problem, or the motivating environmental problems. Secondly, the removal of the barrier cannot take place instantaneously and so a brief jet-like flow is initially induced through the opening between the base of the barrier and the sediment layer. We partially circumvent these difficulties with the classical experiments by implementing a novel dam break barrier release, using a barrier similar to the wrapped-fabric design of [Dalziel, 1993], which minimizes the initial vortical disturbance.

Three-dimensional stereoscopic Particle Image Velocimetry (PIV) measurements allow us not only to capture the velocity field in the laser-plane, but also perpendicular to it. These planar experimental results are compared to the results of the numerical study and the comparison is shown to be good while the simulation successfully converges.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Scase, M.M.
Dodd, N.
Keywords: Sediment transport, dam failures
Subjects: T Technology > TC Hydraulic engineering. Ocean engineering
Faculties/Schools: UK Campuses > Faculty of Engineering
Item ID: 29138
Depositing User: McMullin, Nicholas
Date Deposited: 02 Sep 2015 10:53
Last Modified: 14 Oct 2017 14:13

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