  The Social Force Model (SFM) is a suitable model for describing crowd
behaviors under emotional stress. This research analyzes the role of the body
force in the original SFM. We focused on the parameter associated with the body
stiffness (kn) and its impact on the pedestrian dynamics for two different
geometries: bottlenecks and corridors. Increasing kn produces opposite effects
on the crowd dynamics for each geometry: an increase of the crowd velocity for
bottlenecks, and a decrease for corridors. The former reflects the fact that an
increase in the stiffness reduces the overlap between pedestrians and, as a
consequence, the sliding friction is diminished. This phenomenon reduces the
number of blocking clusters close to the exit door. In the case of the
corridor, instead, due to the confining walls, the pedestrians get tight into a
lattice-like configuration due to space limitations. The friction interaction
with the walls determines the velocity of the whole crowd along the corridor.
Additionally, the corridor geometry generates a flux slowing down for very
crowded environments, as observed in many real-life situations. We also
explored the dimensionless parameters that arose from the reduced-in-units
equation of motion and tuned them to reproduce the qualitative behavior of the
empirical fundamental diagram.
