Simulating Overtopping of seawall defences B.D. Rogers*, M.V. McCabe, P.K. Stansby, D.A. Apsley *RCUK Research Fellow School of MACE
Outline Introduction to Overtopping: • The need for numerical models Numerical Model 1: • Boussinesq-type model • Modification for Seawall Numerical Model 2: • Smoothed Particle Hydrodynamics (SPH) • Effect of the recurvewall Results: • Overtopping events and volumes
Prediction of Wave Overtopping • Physical Models • Empirical Data • Numerical Modelling?
Shallow Water and Boussinesq Equations with a Vertical Wall Boussinesq Terms Dissipation Terms Continuity Equation Momentum Equation Force Imposed by a Wall hwall Fwall u
Shallow Water And Boussinesq (SWAB) Model Validation 7 Wave Overtopping Volumes, Prototype Scale Field Data (from EA) = 3.41m, / = 0.04 H H L 0 0 m0 6 Laboratory Data SWAB Model without Force at Seawall SWAB Model with Force at Seawall /m) 5 3 4 Cumulative Volume (m 3 2 1 0 0 200 400 600 800 1000 1200 Time (s)
ExampleOvertopping and Beach Level at Walcott Link to Movie
Detailed modelling requires SPH Smoothed Particle Hydrodynamics (SPH) Overtopping, flooding and inundation Breaking waves on beaches Plunger Splash up (Photo courtesy of F. Raichlen) Radius of influence Very complex multi-phase multi-scale highly nonlinear problems
The Future: (Multi) Hybrid Chips • Dual-SPHysics (cpu & gpu) – SPEEDUPS of 100 for a Desktop machine = Supercomputer of 1000’s cores • Crespo et al.
In SPH, we know that overtopping is dependent on resolution, so with a much finer resolution this could well produce higher values 3m
Overtopping volumes from SPH Simulations • Results: • With the same bathmetry from the Boussinesq simulations: overtopping events of 2400 litres/m • With the Recurve wall: overtopping event of 540 litres/m • Comparison with Boussinesq & Eurotop
Thank you • Acknowledgements: • Maurice McCabe • Nicolas Chini • Peter Stansby • SeaZone – bathymetry below the low water line • Environment Agency (EA) – beach profile above the low water line