Experimental and computational investigation of the trajectories of blood drops ejected from the nose

P. H. Geoghegan*, C. J.T. Spence, J. Wilhelm, N. Kabaliuk, M. C. Taylor, Mark C. Jermy

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

Blood expirated from the nose may leave a characteristic bloodstain at a crime scene which can provide important clues for reconstructing events during a violent assault. Little research has been done on the typical velocities, trajectories and size distribution that can be expected from expirated blood. An experimental fluid dynamics technique known as stereoscopic particle image velocimetry is used in this work to obtain the air velocity field inside and outside the nostrils during exhalation. A numerical model was then used to compute the trajectory of blood drops of 0.5 and 2 mm. The drops were tracked until ground plane impact below the nostril exit. Three heights were investigated, 1.5, 1.6 and 1.7 m. For an expiration flow rate of 32 l/min in vivo, there is a maximum exit velocity from the nostril of approximately 4 m/s, with a 0.5 m/s difference between nostrils. After the drops have traversed the distances investigated, drops of 0.5 and 2 mm in diameter from both nostrils are at a similar velocity. This implies that the gravitational acceleration after the drops leave the jet has the most influence on velocity. It is however shown that exit velocity does affect impact location. Drop size affects both impact location and impact velocity. An increase in height increases the distance traversed. Compared to the 2-mm drop, the 0.5 mm had a lower impact velocity, but its impact location in the ground plane was further from the nostril exit. Understanding the physics of expirated blood flight allows better interpretation of expirated stains at crime scenes.

Original languageEnglish
Pages (from-to)563-568
Number of pages6
JournalInternational Journal of Legal Medicine
Volume130
Issue number2
Early online date15 Mar 2015
DOIs
Publication statusPublished - 1 Mar 2016

Bibliographical note

© Springer-Verlag Berlin Heidelberg 2015.

Keywords

  • Bloodstain pattern analysis
  • Expirated blood
  • Forensic investigation
  • Nasal cavity
  • Stereoscopic particle image velocimetry

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    • 4 Article
    • 2 Conference contribution

    Experimental measurement of breath exit velocity and expirated bloodstain patterns produced under different exhalation mechanisms

    Geoghegan, P. H., Laffra, A. M., Hoogendorp, N. K., Taylor, M. C. & Jermy, M. C., 1 Sep 2017, In : International Journal of Legal Medicine. 131, 5, p. 1193-1201 9 p.

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  • Visualization of the air ejected from the temporary cavity in brain and tissue simulants during gunshot wounding

    Lazarjan, M. S., Geoghegan, P. H., Taylor, M. C. & Jermy, M. C., 1 Jan 2015, In : Forensic Science International. 246, p. 104-109 6 p.

    Research output: Contribution to journalArticle

  • Experimental investigation of the mechanical properties of brain simulants used for cranial gunshot simulation

    Lazarjan, M. S., Geoghegan, P. H., Jermy, M. C. & Taylor, M., Jun 2014, In : Forensic Science International. 239, p. 73-78 6 p.

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