The Fluid Dynamics of Droplet Impact on Inclined Surfaces with Application to Forensic Blood-Spatter Analysis

As submitted by the applicant: Blood-spatter analysis is a technique used in crime-scene reconstruction to ascertain the point of origin of a bloodstain as well as the method of its creation, e.g., dripping, wiping, or low-to-high-speed impact caused by anything from blunt trauma to cast-off to gunshot wounds. The focus of this research is to study the fluid dynamics associated with droplet impact on planar surfaces of variable roughness, wettability, and absorbency oriented at various angles with respect to the velocity vector of the approaching droplet. In particular, the research will use a coordinated program of careful laboratory experimentation and numerical simulations to examine the influence of multiple parameters associated with droplet impact, with the focus being on the final, steady-state shape of the stain, given its importance to crime-scene reconstruction. The primary problem of interest to the forensic-science community is to determine from the pattern left by the impact of a blood droplet on a surface the droplet size, speed, and angle of impact. Thus, the main goals of the proposed work are to: a) quantify the effects of the surface inclination angle, roughness, wettability, and absorbency, and the initial droplet size and speed on the final observed bloodstain patterns, and b) provide data for the future development of simplified, but relevant phenomenological models of droplet spreading and splashing that can be directly used by practitioners in the field of forensic science. ca/ncf