L. Soldini

Topographically controlled, breaking-wave-induced macrovortices. Part 1. Widely separated breakwaters

In this and the companion paper (Part 2) we examine experimentally, computationally, and analytically the behaviour of breaking-wave-induced macrovortices during startup conditions. Widely separated breakwaters and rip current topographies are chosen as opposite ends of the parameter space. Part 1 examines generation mechanisms using phase-resolving and phase-averaged approximations, and suggests several simple predictive relations for general behaviour. Vortex trajectories and shedding periods for wave breaking on widely spaced breakwaters are also considered in detail. Results show broad agreement with theoretical trajectories. Predictions of vortex shedding periods on breakwater heads show excellent agreement with computations. Part 2 examines startup macrovortices on rip current topographies using computations and laboratory experiments, and changes in behaviour as the system transitions from wide to narrow gap width.

Topographically controlled, breaking-wave-induced macrovortices. Part 2. Changing geometries

This is the second part of a series examining the behaviour of breaking-wave-induced macrovortices. The first part examined theoretically general behaviours during startup conditions, and gave computational results for macrovortex generation and their evolution on widely spaced breakwaters. In this paper, we extend and test qualitatively and quantitatively some of the basic results of Part 1, in particular the initial longshore vortex transport for a wide range of geometries ranging from narrow rip current topographies to isolated breakwaters. Accounting for the presence of a shoreline is found to be necessary for the representation of longshore vortex transport. Results show vortex motion ranging from strongly offshore in the case of a narrow rip current, to strongly longshore in the case of an isolated breakwater. Even with the significant approximations inherent in the analytical predictions, numerical computations using time-domain Boussinesq-type equations and laboratory experiments confirm the trends. Part 3 examines the horizontal mixing features of wave-induced flows over isolated (single-breakwater configuration) or multiple (ripcurrent configuration) submerged structures.

Numerical modeling of the influence of the beach profile on wave run-up

AbstractAn analysis of the run-up over different beach profiles is performed to evaluate the influence of the seabed shape on shore flooding. The analysis was carried out on the basis of numerical solutions of the nonlinear shallow water equations. The chosen solver was shown to provide reliable (both quantitatively and qualitatively) run-up results by comparing numerical solutions (of both solitary and regular waves) with the only available analytical solution forced by a localized topographic change. The run-up patterns on both a natural beach profile and three simpler and schematic profiles derived from it were evaluated. Different wave conditions (both random and groups) were used for a total amount of 96 different cases of inundation. Results are expressed in terms of both maximum (Zmax) and steady-state (Zsteady) run-up. It is found that both types of run-up depend on the offshore variable H0L0, as suggested by several available studies, and that, for all tested cases, random waves induce the larges...

Working of Defense Coastal Structures Dissipating by Macroroughness

The working features of innovative coastal defense structures that can dissipate the energy of incoming waves by the action of large-scale bottom unevennesses (rigid blades covering the lower half of the water depth) were investigated by means of a laboratory experimental campaign. The goal of the study was to characterize the ability of the structures to efficiently reduce the wave height with a minimal change in the mean water superelevations. Similar wave height reductions were achieved for both vertical and inclined blades; their efficiency was slightly superior to that of traditional submerged rubble-mound breakwaters of the same cross-shore extension. For the incident waves examined, very low mean water elevations were observed inshore of the structures, with the inclined blades producing the smallest values. These results suggest that the structures analyzed here could represent an alternative to submerged rubble-mound breakwaters from a hydrodynamic point of view to protect coastlines prone to erosion with minimal risk of dangerous rip currents.

Summertime conditions of a muddy estuarine environment: the EsCoSed project contribution.

As part of the Estuarine Cohesive Sediments (EsCoSed) project, a field experiment was performed in a highly engineered environment, acting as a natural laboratory, to study the physico-chemical properties of estuarine sediments and the associated hydro-morphodynamics during different seasons. The present contribution focuses on the results obtained from the summertime monitoring of the most downstream part of the Misa River (Senigallia, Italy). The measured hydrodynamics suggested a strong interaction between river current, wave forcing and tidal motion; flow velocities, affected by wind waves traveling upstream, changed significantly along the water column in both direction and magnitude. Surficial salinities in the estuary were low in the upper reaches of the estuary and exceeded 10 psu before the river mouth. Montmorillonite dominated the clay mineral assemblage, suggesting that large, low density flocs with high settling velocities (>1 mm s(-1)) may dominate the suspended aggregate materials.

Modelling the Effects of Structures on Nearshore Flows

The effects of defense structure on nearshore water flows are analyzed by means of an efficient and robust flow solver. This is both flexible enough to incorporate bathymetric data typically collected in field surveys and accurate enough to allow for a detailed description of important flow features. Such a tool is believed to be capable of providing useful information for design activities of coastal structures like submerged breakwaters.

Shock trains on a planar beach: quasi-analytical and fully numerical solutions

This study, part of the Special Issue dedicated to the 70th anniversary of Professor Efim Pelinovsky, focuses on a topic that has been central in Professor Pelinovsky’s research, i.e. the analytical and numerical modelling of shallow water waves. We specifically focus on the evolution of trains of shock waves on a planar beach. Antuono (J Fluid Mech 658:166–187, 2011) has, for the first time, proposed a quasi-analytical solution for a train of shock waves forced by a constant Riemann invariant. The present contribution clarifies the validity of such solution and its value for benchmarking nonlinear shallow water equation solvers. Hence, the same tests of Antuono (J Fluid Mech 658:166–187, 2011) have been run by means of the solver of Brocchini et al. (Coast Eng 43(2):105–129, 2001) revealing surprisingly and reassuring good agreements. This provides significant support to the mentioned analytical solution and allows to critically analyse the eventual discrepancies, due to the practicalities of running numerical shallow water solutions (e.g. influence of the boundary conditions, of the numerical resolution, etc.).

Parallel computing for nearshore hydrodynamics

We present the results of an ongoing research about the use of parallel computing for the numerical modelling of nearshore hydrodynamics. An overview is given on strategies for building a parallel, small supercomputer and performing parallel computing. We mainly focus our analysis on the parallelization of the code used to numerically solve the Nonlinear Shallow Water Equation (NSWE) and on the evalution of the performance gained by using a parallel code.