Patrick Comiskey, Ph.D.
Assistant Professor
- Milwaukee WI UNITED STATES
- Mechanical Engineering Department
Dr. Patrick Comiskey is an assistant professor in the Mechanical Engineering Department.
Education, Licensure and Certification
B.S.
Mechanical Engineering
Milwaukee School of Engineering
2014
Ph.D.
Mechanical Engineering
University of Illinois at Chicago
2019
Areas of Expertise
Accomplishments
Faydor Litvin Graduate Honor Award, University of Illinois at Chicago
2017
Graduate Student Council Travel Award, University of Illinois at Chicago
2018
Graduate College Student Presenters Award, University of Illinois at Chicago
2018
Chancellor’s Student Service Award, University of Illinois at Chicago
2018
Social
Selected Publications
A data set of bloodstain patterns for teaching and research in bloodstain pattern analysis: Gunshot backspatters
Data in BriefDaniel Attinger, Yu Liu, Ricky Faflak, Yalin Rao, Bryce A Struttman, Kris De Brabanter, Patrick M Comiskey, Alexander L Yarin
2019
This is a data set of blood spatter patterns scanned at high resolution, generated in controlled experiments. The spatter patterns were generated with a rifle or a handgun with varying ammunition. The resulting atomized blood droplets travelled opposite to the bullet direction, generating a gunshot backspatter on a poster board target sheet. Fresh blood with anticoagulants was used; its hematocrit and temperature were measured. The main parameters of the study were the bullet shape, size and speed, and the distance between the blood source and target sheet. Several other parameters were explored in a less systematic way. This new and original data set is suitable for training or research purposes in the forensic discipline of bloodstain pattern analysis.
Determining the region of origin of blood spatter patterns considering fluid dynamics and statistical uncertainties
Forensic Science InternationalDaniel Attinger, Patrick M Comiskey, Alexander L Yarin, Kris De Brabanter
2019
Trajectory reconstruction in bloodstain pattern analysis is currently performed by assuming that blood drop trajectories are straight along directions inferred from stain inspection. Recently, several attempts have been made at reconstructing ballistic trajectories backwards, considering the effects of gravity and drag forces. Here, we propose a method to reconstruct the region of origin of impact blood spatter patterns that considers fluid dynamics and statistical uncertainties. The fluid dynamics relies on defining for each stain a range of physically possible trajectories, based on known physics of how drops deform, both in flight and upon slanted impact. Statistical uncertainties are estimated and propagated along the calculations, and a probabilistic approach is used to determine the region of origin as a volume most compatible with the backward trajectories.
Hydrodynamics of forward blood spattering caused by a bullet of general shape featured
Forensic Science InternationalPM Comiskey, AL Yarin, Daniel Attinger
2019
A generalized model for the chaotic disintegration of a liquid due to an arbitrarily shaped projectile is proposed. In particular, the model uses percolation theory to predict the fragmentation process of blood, resulting in forward spatter to determine the number of droplets, as well as their sizes and initial velocities resulting from the flow field generated by a 7.62 × 39 mm and a 0.45 auto bullet. Blood viscoelasticity, which slows down the initial velocities of the droplets, is accounted for. The main physical mechanisms responsible for the chaotic disintegration of blood in the case of forward spattering are (i) the Rayleigh-Taylor instability associated with denser blood accelerating toward lighter air and (ii) a cascade of instability phenomena triggered by the original Rayleigh-Taylor instability because the Reynolds number is of the order of 107.
Self-similar turbulent vortex rings: interaction of propellant gases with blood backspatter and the transport of gunshot residue
Journal of Fluid MechanicsPM Comiskey, AL Yarin
2019
Self-similar turbulent vortex rings are investigated theoretically in the framework of the semi-empirical turbulence theory for the modified Helmholtz equation. The velocity and vorticity fields are established, as well as the transport of passive admixture by turbulent vortex rings. Turbulent vortex rings of propellant gases originating from the muzzle of a gun after a gunshot are an important phenomenon to consider in crime scene reconstruction. In this work, it is shown that this has a significant repercussion on the outcome of backward blood spatter resulting from a gunshot. Turbulent vortex rings of propellant gases skew the distribution of bloodstains on the ground and can either propel blood droplets further from the target, or even turn them backwards towards the target.
Hydrodynamic focusing in porous media and its ramifications on the critical penetration depth
Physics of FluidsPM Comiskey, C Staszel
2021
The effect of hydrodynamic focusing through a surface with multiple pores is investigated. The flow field of a single drop impacting a surface with n number of pores is established by solving the Laplace equation as a result of an instantaneous pressure impulse with complex analysis. The liquid velocity penetrating into the pores is derived and applied to find the critical penetration depth at which the impacting liquid ceases motion. It was found that the liquid penetration velocity rapidly diminishes as the number of pores increases. Implications for liquids splashing onto garments and the corresponding critical thickness such that liquid does not completely penetrate are discussed.
