Influence of forces on vehicle’s instability in floodwaters

Flood hazards to vehicle have become more frequent and noticeable in the recent years. Therefore, this paper aims at estimating the forces observed on a partially submerged vehicle in floodwater, namely frictional, buoyancy, lift and drag forces. An understanding of the relevant forces involved is necessary to attempt to characterize the instability thresholds of vehicles in floodwater flows. With that regards, a model vehicle with the scale ratio of 1:24 was used and a series of flume experiments were conducted. While determining the vertical pushing force, the influence of lift force was found insignificant due to sub-critical state of the flow. Moreover, the critical water depth at which the up-thrust force governed was observed when the water depth exceeded 0.042 m. Below critical depth, the vehicle stability governed unless the drag force imposed by the flowing water was lower than the frictional force between the tires and floodplain surface. Keywords: Hazard, Vehicle instability, Partially submerged vehicle, Floodwater