Fluid-Structure Interaction of a Partially Submerged Body: an Analytical Model for the Human Stability in Floodwaters

Climate change is increasing the number of extreme events, like floods or long-lasting rainfalls, in densely inhabited area, this focusing the attention on the safety of human being in flooded urban areas. The stability of people subjected to floodwaters is an important aspect to evaluate people’s safety. To this aim, many theoretical and experimental works analyze human stability using simplified and conservative approaches, although the role of body articulation and posture on human stability in floodwaters is relevant. We here propose simple analytical models to evaluate the effect of flood impact on a human body with different postures, composed by a two-dimensional frame of three beams, which represent different parts of the human body with variable orientation. The body stability is described by means of a dynamic equilibrium of the system, which accounts for a tilting moment generated by the toppling mechanism induced by floodwater conditions, and a resisting moment that changes with the body posture and the inertial characteristics of each beam. The model results are compared with recent laboratory experiments, where a human body at a quasi-natural scale was reproduced and subjected to several floodwater scenarios. Results show how the posture of the human body can provide a significant contribution to the stabilizing moment in the case of backward toppling.