Numerical Assessment of Tsunami Forces on Vertical Wall Structures: Impact of Inundation Depth and Incident Fluid Velocity

Abstract

This study evaluates the tsunami forces exerted on a terrestrial structure caused by a collision-induced tsunami. Conventionally, assessing these forces relies on the inundation depth of the colliding tsunami passing without the presence of the terrestrial structure. However, it is essential to consider the inundation depth and incident fluid velocity, as both significantly influence the resulting tsunami forces. In this research, ANSYS Fluent 17.2 is employed to simulate excitation sources using a Defined Function (UDF) code within a C++ framework. The dynamic meshing technique is adopted to replicate the interactions between the bore pressure of the tsunami and an idealised vertical wall structure across three distinct water levels. Computational Fluid Dynamics (CFD) modelling demonstrates the proposed methodology's capability to offer precise impact pressure distributions concerning geographical and temporal aspects. The findings reveal specific instances: at a water depth of 10 m, the maximum Froude number is attained at 3.5 and 6.9 seconds, corresponding to a maximum pressure value of 3.9x105 Pa at 3.85 seconds for a water flow velocity of 20 m/sec. Similarly, for a water depth of 12 m, the most significant Froude number is observed at 3.95 and 6.9 seconds, with a peak pressure value of 1.8x105 Pa at 4.6 seconds, associated with a water flow velocity of 15 m/s. Additionally, at a water depth of 14 m, the maximum Froude number is reached at 4.95 and 7.1 seconds, accompanied by a maximum pressure value of 7.4x104 Pa at 4.85 seconds for a water flow velocity of 10 m/s.