Impact of hydrodynamic forces on a static vehicle at varying Froude numbers under partial submergence and subcritical flow conditions

Roads are often the first assets affected by inundations which usually ends up as a serious hazard to the traffic. A vehicle, when submerged in floodwaters, is affected by several hydrodynamic forces, namely frictional, buoyancy, lift and drag forces. An understanding of the relevant forces involved is necessary to attempt to characterize the stability thresholds of vehicles in floodwaters. With that regards, a series of flume experiments were conducted on a static scaled model vehicle, Volkswagen Scirocco (1:24) which ensured the similarity laws. To assess the limiting thresholds that could lead to the stability failure modes, the vehicle was controlled to be partially submerged under the subcritical flow conditions. The vehicle was placed at the same domain with different orientations, namely 0°, 45°, 90°, 135°, 180°, 225°, 270°, 315° and 360° for each run to reduce inconsistencies in the test data. Based on the varying hydraulic variables assessed from the experimental runs, the hydrodynamic forces were theoretically estimated. Later, the relation between the hydrodynamic forces at varying Froude numbers was determined. From the study outcomes, an inverse relation of Froude number with respect to buoyancy force was noticed. On the other hand, an increment in the lift force slightly increased the Froude number. Similarly, a positive trend between the drag and frictional forces with respect to the Froude number was witnessed.