Dynamics of vehicle debris during a flood. Incipient motion conditions and numerical experiments.

Chiara Arrighi, Juan Carlos Alcèrreca Huerta, Hocine Oumeraci, Fabio Castelli

Monday 29 june 2015

15:05 - 15:20h at Asia (level 0)

Themes: (T) Special session, (ST) Flood defences and flood risk: hydraulic engineering aspects

Parallel session: 2E. Special session: Flood Risk and Flood defences

Many of the recent flood events have illustrated why vehicle debris represents one the most exacerbating factors for flood risk in urban areas, particularly for people’s safety. In this study, the incipient motion conditions of flooded vehicles are investigated and discussed. A mobility parameter _V, depending on the shape and on the immersed weight of the vehicle, is introduced and represented in a non-dimensional diagram versus the Froude number of the flow. A 3-dimensional numerical model describing the flow for different regimes past a specific and detailed vehicle geometry is presented to clarify the contribution of drag and lift forces to the incipient motion of the vehicle. The results highlight the dominant influence of the Froude number on the forces coefficients with differences in the effects on the drag and lift coefficients. The numerical results are compared with recent experiments found in literature on partially submerged vehicles. The comparison confirms the crucial role of the friction coefficient and reveals the uncertainties introduced assuming the car as a rigid body. Moreover, a preliminary study of the dynamics of vehicle debris is presented. The estimated force coefficients and the knowledge of the vehicle-flow interaction may provide a useful tool for flood risk assessment and management in urban areas.