Blood backspatter drops moving toward the shooter can land behind the victim due to interaction with propellant gases

The theoretical/numerical results of the present work reveal a significant interaction of the oncoming vortex ring of propellant muzzle gases with backward blood spatter, especially in cases of the short-range shooting, it is shown that there is even possibility that a blood drop from the backspatter will fully turn around by a powerful turbulent vortex ring and land behind a victim. Such a theoretically predicted outcome is confirmed by experimental data of fully reversed drop trajectories observed in the experiments. A parametric study conducted in this work reveals the totality of the outcomes of the vortex ring interaction with the backward blood spatter and the resulting deflections and landing locations of blood drops. Furthermore, a secondary vortex ring is considered here too to account for a continuous effect of the propellant gas. The trajectories of multiple blood drops whose initial conditions are determined by the Rayleigh-Taylor instability are predicted up to their landing locations on the floor accounting for the gravity force and the drag force they experience from the surrounding air and the vortex ring/rings propagating from the rifle in the opposite direction. The pair of parameters which characterize the self-similar turbulent vortex rings, namely α associated with the semi-empirical turbulence model used and the vortex impulse P₀, can be established using the experimental data for each type of weapon.