Modelling Storm Surge Wave Overtopping of Seawalls with Negative Freeboard (original) (raw)
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Wave overtopping models and seawall freeboards
Unless the maximum wave run-up, R max on the face of a seawall is greater than the freeboard of the structure, R c , then there is no overtopping (apart from wind-blown spray). This condition is satisfied in a new theoretical model of random wave overtopping developed by Hedges and Reis 1 .
COMPARISON OF NUMERICAL MODELS FOR WAVE OVERTOPPING AND IMPACT ON A SEA WALL
Coastal Engineering Proceedings, 2014
The paper discusses three different numerical models in a study of wave overtopping and impact on a sea wall. The models used are SWASH (based on the nonlinear shallow water equations), DualSPHysics and FLOW-3D (both based on the full Navier-Stokes equations). The models are validated against experimental measurements in a setup with a quay wall and berm in front of the sea wall. The two models based on the full Navier-Stokes equations provide good estimates of the wave impact on the sea wall. Moreover, reasonable agreement with experimental values of averaged overtopping discharges was found for the full test time series simulated with FLOW-3D. Notwithstanding the SWASH model provides reasonable estimates for the wave overtopping on a simple quay wall, at a significantly lower computational cost than the other two models, it clearly underrates the overtopping discharge in the case of a combination of a quay wall, berm and sea wall. Further investigation is needed to draw conclusions on the model accuracy of SWASH in such a case.
Numerical Analysis of Wind Effect on Wave Overtopping on a Vertical Seawall
Water
Onshore wind significantly affects wave run-up and overtopping, thereby representing a major variable to account for in the design process. The aim of this study is to analyze the ability of numerical models to properly reproduce the wind effect on the overtopping at vertical seawall and to use them to understand how the wind influences the overtopping process as well. We use the RANS model, FLOW-3D, and the NLSW model, SWASH; both model the action of wind through the shear stress that it exerts on the sea surface. Although a simplified modelling of wind has been adopted, the CFD model has led to physically consistent results. On the other hand, SWASH seems to be unsuitable for reproducing the enhancement of the overtopping rate due to wind. CFD numerical results show that the wind affects only the lower overtopping regime (i.e., q < 1 l/s/m); as the mean overtopping discharge decreases, the influence of wind increases. Specifically, wind plays a key role in pure “white overtoppi...
The Reduction of Wave Overtopping by Means of a Storm Wall
Coastal Engineering Proceedings
A second edition of the EurOtop manual, a manual on wave overtopping of sea defenses and related structures, became available as pre-release in October 2016 on the website www.overtopping-manual.com. One of the improvements in this manual is based on the material in the current paper: how wave walls can reduce wave overtopping discharges. The base data set for the original advice in the previous EurOtop from 2007 is compared to the new developed procedures and new (unpublished) data collected in the wave flume of Ghent University. The comparative study shows that the differences are due to hydraulic differences in the test program. The original dataset from 1994 has tests with the still water level SWL both above and below the foot of the wall and was analyzed with an average slope analysis, where the UGent dataset only has tests with SWL below the foot of the wall and the small wall on top of the dike slope did not influence the average slope so that the actual slope could be used....
Wave Runup and Overtopping at Seawalls Built on Land and in Very Shallow Water
Journal of Waterway, Port, Coastal, and Ocean Engineering, 2013
The current study proposes prediction formulas both for random wave runup and mean overtopping discharge at seawalls constructed on land or in very shallow water. Although several existing formulas for runup and overtopping use the incident wave characteristics at the toes of seawalls, this study adopts the equivalent deepwater wave characteristics and an imaginary seawall slope for easy application of the formulas, especially in relation to seawalls constructed on land. The prediction formulas for overtopping use the predicted runup values. For the wave runup prediction formulas two sets of experimental data are used; i.e., a new set of data and the data obtained in a previous study. For the wave overtopping prediction formulas, the experimental data measured in a previous study are used. Comparisons with measurements show good performances of both new prediction methods.
Coastal Engineering, 2000
A one-dimensional high-resolution finite volume model capable of simulating storm waves propagating in the coastal surf zone and overtopping a sea wall is presented. The model Ž. Ž. AMAZON is based on solving the non-linear shallow water NLSW equations. A modern upwind scheme of the Godunov-type using an HLL approximate Riemann solver is described which captures bore waves in both transcritical and supercritical flows. By employing a finite volume formulation, the method can be implemented on an irregular, structured, boundary-fitted computational mesh. The use of the NLSW equations to model wave overtopping is computationally efficient and practically flexible, though the detailed structure of wave breaking is of course ignored. It is shown that wave overtopping at a vertical wall may also be approximately modelled by representing the wall as a steep bed slope. The AMAZON model solutions have been compared with analytical solutions and laboratory data for wave overtopping at sloping and vertical seawalls and good agreement has been found. The model requires more verification tests for irregular waves before its application as a generic design tool.
Effect of Crest Elevations on the Overtopping Discharges Over Composite Seawall
Proceedings of ... Conference on Coastal Engineering, 2017
Overtopping discharges over a composite seawall model has been studied experimentally. Effect of crest elevations on the overtopping discharges was studied based on the new data set of 132 tests. Test data is compared to the existing formulas given by EurOtop Manual (2007) and EurOtop II Manual (2016). Results showed that both EurOtop Manual (2007) and EurOtop II (2016) formulas for composite seawalls are applicable to our test setup with a roughness coefficient of 0.55 which corresponds a rubble mound composite structure with two layers and an impermeable core. Vertical wall caused the composite structure act as an impermeable structure. Height of the storm wall was raised 2, 4, 6, 8, and 10 cm successively during the tests. Results showed that a reduction rate clearly depends on the wave steepness.
Design of the US Wave Overtopping Simulator
2009
The US Wave Overtopping Simulator has to simulate overtopping discharges up to 2 cfs/s/ft for wave conditions of respectively 8 ft with a peak period of 14 s and 3 ft with a period of 6 s. This requires a Simulator which is in size about three times larger than the existing Dutch one. This report describes the theory of waves overtopping the crest of a levee, the design of the Simulator, how to operate it and possible ways to measure hydraulics during testing. We know a lot about wave overtopping over levees, but still there are discrepancies between various formulae. First the existing theory is given about wave overtopping discharge and individual wave overtopping volumes. This leads to the distributions of wave overtopping volumes that have to be simulated by the Simulator. Then flow velocities, flow depths and flow times or durations of overtopping wave volumes at the crest of a levee have been discussed, including re-analysis of existing work and some recent research. The concl...
Comparisons of wave overtopping at coastal structures calculated with AMAZON, COBRASUC and SPHYSICS
The use of numerical models to calculate the mean overtopping discharges is, nowadays, more frequent in preliminary design of coastal structures, since they are more flexible than both empirical/semi-empirical and physical models and, once calibrated and validated, they can be applied reliably to a large range of alternative structure geometries and wave conditions. There are different models that can be used to calculate the mean overtopping discharges over a structure. The paper compares the output from three numerical models used to predict the mean overtopping discharges: AMAZON [1], based on solving the non-linear shallow-water equations; and two models based on Reynolds averaged Navier-Stokes equations, COBRAS-UC [2], a Eulerian model using the volume of fluid (VoF) method for surface capturing, and SPHysics [3], a Lagrangian model based on Smoothed Particle Hydrodynamics (SPH). The numerical results are also compared with experimental data obtained at the National Civil Engin...
Modeling Wave Overtopping on a Seawall with XBeach, IH2VOF, and Mase Formulas
Water
The advances in computational fluid dynamics have made numerical modeling a reliable complementary tool to the traditional physical modeling in the study of the wave overtopping phenomenon. This paper addresses overtopping on a seawall by combining the numerical models XBeach (non-hydrostatic and Surfbeat modes) and IH2VOF, and the Mase formulas. This work is structured in two phases: (i) phase I assesses the performance of numerical models and formulas in modeling wave run-up and overtopping on a seawall for a solid profile bottom and representative hydro-morphologic conditions of a study site in the Portuguese west coast; (ii) phase II investigates the effect of the profile bottom variation in the overtopping phenomenon for extreme maritime storm field conditions of the study site, considering a solid bottom and a varying sandy bottom. The results indicate that XBeach underestimates the wave energy, and the frequency and intensity of the overtopping occurrences predicted by IH2VOF...