Experimental validation of a numerical model for predicting the trajectory of blood drops in typical crime scene conditions, including droplet deformation and breakup, with a study of the effect of indoor air currents and wind on typical spatter drop trajectories  N. Kabaliuk, M.C. Jermy, E. Williams, T.L. Laber, M.C. Taylor  Forensic Science International  Volume 245, Pages 107-120 (December 2014) DOI: 10.1016/j.forsciint.2014.10.020 Copyright © 2014 Elsevier Ireland Ltd Terms and Conditions

Fig. 1 Blood drop velocities versus sizes relative to the terminal velocity data for water drops ([27]). Forensic Science International 2014 245, 107-120DOI: (10.1016/j.forsciint.2014.10.020) Copyright © 2014 Elsevier Ireland Ltd Terms and Conditions

Fig. 2 Drop trajectory segment (left) and force balance segment diagram (right): initial drop velocity vo with initial inclination angles αo, βo and γo; L, H and Z are the lengths of drop trajectory along coordinate axes. Forensic Science International 2014 245, 107-120DOI: (10.1016/j.forsciint.2014.10.020) Copyright © 2014 Elsevier Ireland Ltd Terms and Conditions

Fig. 3 Diagram of a deformed drop with the diameters of major (perpendicular to the direction of drop motion) and minor (parallel) axes of the deformed drop dmax and dmin and its shape at equilibrium (the volumes of an undisturbed and deformed drop are Vo=(π/6)d03 and V=(π/6)dmax2dmin respectively. From volume conservation considerations (assuming no significant evaporation occurs): d03=dmax2dmin. The aspect ratio and cross-sectional (projected) area of a deformed drop are AR=dmin/dmax=d03/dmax3 and A=π4dmax2=π4d03/dmax3). Forensic Science International 2014 245, 107-120DOI: (10.1016/j.forsciint.2014.10.020) Copyright © 2014 Elsevier Ireland Ltd Terms and Conditions

Fig. 4 Interpolated and experimentally obtained [41] drag coefficients for drops at terminal velocities with the sphere and disk drag coefficients from Clift et al. [20] and Massey et al. [33]. Forensic Science International 2014 245, 107-120DOI: (10.1016/j.forsciint.2014.10.020) Copyright © 2014 Elsevier Ireland Ltd Terms and Conditions

Fig. 5 Comparison of numerical and empirical terminal velocities and corresponding deformation levels for water drops. The lower four data sets represent numerical predictions [50–54]. Forensic Science International 2014 245, 107-120DOI: (10.1016/j.forsciint.2014.10.020) Copyright © 2014 Elsevier Ireland Ltd Terms and Conditions

Fig. 6 Empirical and numerical fall velocity of a Ø4.94mm passive blood drop. The dataset extreme line was fitted through the measured velocity data extreme points. The black points are the moving average of the processed data. Forensic Science International 2014 245, 107-120DOI: (10.1016/j.forsciint.2014.10.020) Copyright © 2014 Elsevier Ireland Ltd Terms and Conditions

Fig. 7 Initial oscillations of passive blood drops observed experimentally. Forensic Science International 2014 245, 107-120DOI: (10.1016/j.forsciint.2014.10.020) Copyright © 2014 Elsevier Ireland Ltd Terms and Conditions

Fig. 8 Frequency and period of passive blood drop oscillations. Forensic Science International 2014 245, 107-120DOI: (10.1016/j.forsciint.2014.10.020) Copyright © 2014 Elsevier Ireland Ltd Terms and Conditions

Fig. 9 Passive blood drop shapes and aspect ratios after 1.5m of fall: (a) satellite, (b) needle and (c) hose connector drops. Standard deviation of the aspect ratio measurements was ±0.3. Forensic Science International 2014 245, 107-120DOI: (10.1016/j.forsciint.2014.10.020) Copyright © 2014 Elsevier Ireland Ltd Terms and Conditions

Fig. 10 Experimental and numerical results for the initial oscillation of a 5.34mm diameter passive blood drop. Initial distortion yo and distortion rate y˙o used for the simulation were 0.076 and 55s−1 correspondingly). Forensic Science International 2014 245, 107-120DOI: (10.1016/j.forsciint.2014.10.020) Copyright © 2014 Elsevier Ireland Ltd Terms and Conditions

Fig. 11 Superimposition of cast-off drop images. The disk rotates clockwise. Forensic Science International 2014 245, 107-120DOI: (10.1016/j.forsciint.2014.10.020) Copyright © 2014 Elsevier Ireland Ltd Terms and Conditions

Fig. 12 Weber number for the 0.4–4mm cast-off drops studied. Forensic Science International 2014 245, 107-120DOI: (10.1016/j.forsciint.2014.10.020) Copyright © 2014 Elsevier Ireland Ltd Terms and Conditions

Fig. 13 Empirical (bold solid and dashed black lines) and numerical cast-off blood drop trajectories at We=0.4 and 2. Forensic Science International 2014 245, 107-120DOI: (10.1016/j.forsciint.2014.10.020) Copyright © 2014 Elsevier Ireland Ltd Terms and Conditions

Fig. 14 Highly deformed impact drops observed: a–d=1.4mm, AR=0.67, We=9.7; b – 0.9mm, 0.86, 5.6; c – ‘liquid bag’ 1.54mm, 0.75, 10.4; d – 0.68mm, 0.92, 4.6; e – 0.9mm, 0.86, 5.8; f – 1.6mm, 0.37, 9; g – ‘liquid bag’ 1.5mm, 0.6, 8.4. Forensic Science International 2014 245, 107-120DOI: (10.1016/j.forsciint.2014.10.020) Copyright © 2014 Elsevier Ireland Ltd Terms and Conditions

Fig. 15 Aspect ratios versus Weber numbers for impact drops studied. Forensic Science International 2014 245, 107-120DOI: (10.1016/j.forsciint.2014.10.020) Copyright © 2014 Elsevier Ireland Ltd Terms and Conditions

Fig. 16 Examples of vibrational (a) and bag (b) impact blood drop breakup (drop movement is from left to right). Forensic Science International 2014 245, 107-120DOI: (10.1016/j.forsciint.2014.10.020) Copyright © 2014 Elsevier Ireland Ltd Terms and Conditions