Roughness Coefficient for 2-D Simulation of Tsunami Inundation over Building Area

Abstract

In this study an equivalent roughness coefficient including the effect of drag caused by structures as well as a bottom friction is investigated for flooded building areas. In order to quantify the equivalent roughness coefficient for a given building area, the flows through regularly spaced unsubmerged square piers are simulated using the RANS equation model of FLOW-3D, a 3-dimensional computational fluid dynamics code. The Manning`s n-value is evaluated by applying the computed data into the Manning`s equation. The calculated Manning`s n-value is compared with the results obtained from both hydraulic experiments and the semi-analytical formula derived from momentum analysis including drag interaction effects, and a good agreement is achieved. It is found from the computational results that the Manning`s n-value is strongly dependent on the interval of piers. It is also found that the equivalent Manning`s n-value increased with 2/3 power of water depth.