Development of a RANS Numerical Model for Nearshore Morphodynamics

Abstract:

Beach profile evolution is of great importance for the estimation of changes in the coastline. It is also tightly related to the impact of extreme events and their consequences. Some of the aspects of the cross-shore evolution are not well known. This leads to important uncertainties in the predictions provided by numerical models. Currently, different techniques (empirical formulae, physical modeling, numerical modeling and field campaigns) are being used to study the beach profile evolution, aiming to provide a better understanding of the interaction between nearshore hydro and morphodynamics, and how do they result in the bathymetry evolution. Each of these techniques has its limitations in terms of precision, cost or quality and resolution of the obtained results.

The main objective of this work is to develop a numerical model that offers a compromise between precision and computational cost for the simulation of nearshore processes, providing a new tool for the detailed analysis of the cross-shore beach profile evolution. It is also intended to restrict the input parameters to the physical properties of the sediment, resulting in a more predictive model.

The numerical model consists of a 2D RANS hydrodynamic model (IH2VOF) coupled with a newly developed One-Phase Eulerian sediment transport module which accounts for both bedload and suspended mechanisms. The hydrodynamic model has also been parallelized to run on multiple CPU cores, resulting in better computing capabilities.

The model has been validated with experimental results of the generation and development of a breaker bar, showing a good agreement for the resulting cross-shore profile as well as the involved hydrodynamics. The computational cost has been significantly reduced if compared with similar models. Besides, an analysis of the resulting data has been performed to provide extra insight into the interaction between hydrodynamics and morphology.