| Summary: | The extensive research on the influence of sea dike geometry on tsunami-induced scour indicates the necessity for a suitable model that can forecast the scour depth behind coastal structures and thus minimize the damaging effect of a high category tsunami occurrence. Current attempts to study this phenomenon have not gained worldwide acceptance and have been limited to unproven analytical methods, and either laboratory or numerical methods. These indicate the need for a verifiable predictive expression that links both the sediment characteristics and coastal defence geometry. A comprehensive laboratory experiment was conducted to better understand the propagation mechanism of tsunami waves around four varying dikes sizes; two of which were modelled after dikes in Iwanuma and Soma cities in Japan that were affected by the 2011 Great Eastern Japan Earthquake and Tsunami. This investigation contributed to the understanding of the influence of dike dimensions on the flow variables. Afterwards, the mechanism of the induced local scour at the landward region was studied in detail because of the destructive impact it could have on the stability of the structures. These led to the development of a predictive scour model, from which a tsunami-induced scour resilient structure can be proposed. Also, using the particle size analysis, the median grain size and permeability properties of the sediment grain were determined and used to form the boundary condition of the expression. The two-dimensional CFD analyses of the wave propagation and associated induced scour were investigated using ANSYS Fluent software package and sedFoam-2.0 solver respectively, and the results validated against the laboratory data showed good agreement. The Reynolds-Averaged Navier-Stokes (RANS) modelling approach with Realizable k-ε turbulence model and scalable wall function for wall modelling were employed for the wave flow, while turbulence-averaged Eulerian two-phase flow equations with the kinetic theory of granular flows for intergranular stress models and a k-ε turbulence model were used for the numerical implementation of the sediment scour.
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