Hydrodynamic Loading of Dutch terraced houses due to flood actions using Computational Fluid Dynamics

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Whenever a region - especially the coastal area - is affected by flood risk, it is essential for residential and life protection to gain knowledge about the mechanisms leading to the collapse of houses. There are empirical mortality functions to predict the mortality of population in the Netherlands directly affected by flooding, but due to probable changes in building quality it is necessary to investigate the fragility of the current building stock. For a detailed structural research containing collapse mechanisms, the resulting loads on buildings in case of flooding – depending on flow velocity, water height, building orientation, width, height etc. – should be known. In current research, several physical experiments have been conducted in order to gain information about hydrodynamic loads on houses in flood actions. The present project aims to set up a numerical model for assessing the flow-induced pressure loads on residences. The model is based on physical experiments already conducted in model scale: a dam break wave is generated, impacting on a model residence of typical Dutch dimensions; then the flow-induced pressure loads are determined. The focus is on the quasi-steady flow part after the initial wave impact. For moderate computational load Reynolds-averaged equations are used for the numerical model. The generated flow conditions and load magnitudes are compared to physical results in order to validate the numerical model. It can be shown that the results generated during the quasi-steady flow part conform with physical results largely. Appearing discrepancies may result from model constraints regarding strongly mixed interface regions of air and water. Finally, possible further model applications are demonstrated: the effect of urban density (realised by blockage ratio variation) on the resulting load is investigated; in addition, the experiment is scaled to prototype scale. Generally, the numerical model serves as a useful tool for load estimation induced by the quasi-steady part of a dam break wave. The model can be used to investigate further modifications; a large range of input variables like e.g. flow conditions, residence geometries, residence arrangements can be assessed to gain information about main interrelations or specific scenarios.