CFD Simulation of a Tsunami Impacting a Coastal City Including Numerous Buildings

Abstract

This work has been performed within the framework of the national project Tandem (2014–2017), with the aim to improve knowledge about tsunami risk on the French coasts. In this project, Principia works especially on the validation of the in-house EOLE CFD software for the simulation of tsunamis. The code solves 3D multi-phase flows on multi-blocks structured meshes coupled with a free surface tracking VOF model. Many validations have been carried out on academic test cases of wave generation, propagation, run-up and submersion. A focus has been especially done on the ‘macro-roughness’ modelling, namely the influence of buildings of significant size on the tsunami wave propagation. Two different approaches for the ‘macro-roughness’ modelling have been studied and compared, the classical projected boundary method, where only the building’s walls are discretized and its influence on the flow is taken into account by the no-slip boundary condition applied on these walls, and the immersed boundary method where a solid colour function assigns the solid/fluid ratio in each cell of the mesh. Due to their different nature, both methods present specific advantages and drawbacks (meshing set-up and topological constraint, accuracy, CPU time). Comparisons are carried out between the two macro-roughness models, and with a test case for which data issued from an experience on a city at a 1/50 scale are available.