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Figure 7: (a) Reconstruction of the trajectories of four bloodstains using straight trajectories vs. ballistic trajectories; the geometry (locations of the stains, of the victim, impact angles) in (a) is reproduced from teaching material graciously provided by H. McDonell. Drops size is assumed to be 3mm, implying velocities in the interval 5.3-7.5 m/s. (b) definition of the angle of impact o and directional angle y. flight of drops.

Figure 7 (a) Reconstruction of the trajectories of four bloodstains using straight trajectories vs. ballistic trajectories; the geometry (locations of the stains, of the victim, impact angles) in (a) is reproduced from teaching material graciously provided by H. McDonell. Drops size is assumed to be 3mm, implying velocities in the interval 5.3-7.5 m/s. (b) definition of the angle of impact o and directional angle y. flight of drops.

Related Figures (18)

Figure 1: BPA uses FD-based methods to reconstruct a bloodletting event. In the above crime scene investigated by one of the co-authors, C.M., various bloodstain patterns are visible, namely a poo (AE), transfer stains (AB), flow patterns (AA) and several drip stains (AD). Elliptical bloodstains (B. indicate the area of origin of a blood spatter, see section 5. For a description of what happened in the photographed crime scene, refer to section 8.
Figure 1: BPA uses FD-based methods to reconstruct a bloodletting event. In the above crime scene investigated by one of the co-authors, C.M., various bloodstain patterns are visible, namely a poo (AE), transfer stains (AB), flow patterns (AA) and several drip stains (AD). Elliptical bloodstains (B. indicate the area of origin of a blood spatter, see section 5. For a description of what happened in the photographed crime scene, refer to section 8.
Figure 2: Wetting angle 0 on a hydrophobic target (a, such as an oily, plastic or waxed surface) and on a hydrophilic target (b, such as clean glass). The wetting angle is measured at the three-phase line, which is the location where the air (A), the liquid (L) and the solid (S) meet. Drop impact and stain formation depend on wettability. Figure 2: Wetting angle Gon a hydrophobic target (a, such as an oily, plastic or waxed surface) and on a
Figure 2: Wetting angle 0 on a hydrophobic target (a, such as an oily, plastic or waxed surface) and on a hydrophilic target (b, such as clean glass). The wetting angle is measured at the three-phase line, which is the location where the air (A), the liquid (L) and the solid (S) meet. Drop impact and stain formation depend on wettability. Figure 2: Wetting angle Gon a hydrophobic target (a, such as an oily, plastic or waxed surface) and on a
Table 2: Forces and typical dimensionless parameters used to describe FD phenomena, with typica magnitudes in BPA cases.
Table 2: Forces and typical dimensionless parameters used to describe FD phenomena, with typica magnitudes in BPA cases.
Figure 3: Determination of the drag force as a function of the velocity of a drop moving through quiet air. Dimensional plot (a) versus non-dimensional plot (b). Note that in (b) all the datapoints collapse onto the single line of Eq. (3) when reported using dimensionless numbers. In the photographs, the general flow direction is from left to right, and particles added to the fluid (from [32, 33], with permission from publisher) follow the fluid flow around a sphere. that one dimensionless curve replaces several dimensional curves.
Figure 3: Determination of the drag force as a function of the velocity of a drop moving through quiet air. Dimensional plot (a) versus non-dimensional plot (b). Note that in (b) all the datapoints collapse onto the single line of Eq. (3) when reported using dimensionless numbers. In the photographs, the general flow direction is from left to right, and particles added to the fluid (from [32, 33], with permission from publisher) follow the fluid flow around a sphere. that one dimensionless curve replaces several dimensional curves.
Figure 4: Semi-dimensionless plot to determine the impact velocity of a falling droplet as a function of droplet diameter, dy, and initial droplet velocity, v9, for a vertical path (trajectory) of 1m. The initial velocity points downwards. Note that both axes are non-linear to better display the data, and that detailed instructions to use the plot are in Appendix B. Both the impact velocity (thin contours in the body of the plot) and the initial velocity are given in a non-dimensional manner, as ratios over the terminal velocity. The terminal velocity Vierminal iS the violet curve, with values on the vertical axis, right. The thick lines delineate various physical regimes, identified with squared numerals and described in Table 3 and point b below.
Figure 4: Semi-dimensionless plot to determine the impact velocity of a falling droplet as a function of droplet diameter, dy, and initial droplet velocity, v9, for a vertical path (trajectory) of 1m. The initial velocity points downwards. Note that both axes are non-linear to better display the data, and that detailed instructions to use the plot are in Appendix B. Both the impact velocity (thin contours in the body of the plot) and the initial velocity are given in a non-dimensional manner, as ratios over the terminal velocity. The terminal velocity Vierminal iS the violet curve, with values on the vertical axis, right. The thick lines delineate various physical regimes, identified with squared numerals and described in Table 3 and point b below.
Figure 5: Early attempts of visualizing drop impact. (A-B) show various shapes assumed by a drop of milk impacting on a glass target, as sketched in 1876 by Worthington, without a camera, but with the help of an electrical spark generator and of his retinal persistence. Hand-drawn sketches show ring accumulation during the impact, splashing and the formation of spines [53, 54].
Figure 5: Early attempts of visualizing drop impact. (A-B) show various shapes assumed by a drop of milk impacting on a glass target, as sketched in 1876 by Worthington, without a camera, but with the help of an electrical spark generator and of his retinal persistence. Hand-drawn sketches show ring accumulation during the impact, splashing and the formation of spines [53, 54].
Figure 6: (a-c) High-speed visualization of the cascade of events leading to the formation of drops during the breakup of a liquid sheet, reproduced with permission from the Midwest Forensic Center [49, 73]. Plateau- Rayleigh instabilities tend to minimize surface area and can break a liquid jet into drops, as in picture (d) reproduced with permission [74, 75].
Figure 6: (a-c) High-speed visualization of the cascade of events leading to the formation of drops during the breakup of a liquid sheet, reproduced with permission from the Midwest Forensic Center [49, 73]. Plateau- Rayleigh instabilities tend to minimize surface area and can break a liquid jet into drops, as in picture (d) reproduced with permission [74, 75].
Figure 8: Examples of how uncertainties on physical parameters influence the determination of the area of origin of a blood spatter: (a) Effect of uncertainty in the impact angle; (b) effect of uncertainty in impact velocity; (c) effect of uncertainty in drop diameter; d) estimated heights of area of origin for initial conditions reported in Figure 7 and Figure 8. In figures (a-c), the baseline case is the same as in Figure 7, while a representative error of +10% is assumed for the overestimation curve, and of -10% for the underestimation curve.
Figure 8: Examples of how uncertainties on physical parameters influence the determination of the area of origin of a blood spatter: (a) Effect of uncertainty in the impact angle; (b) effect of uncertainty in impact velocity; (c) effect of uncertainty in drop diameter; d) estimated heights of area of origin for initial conditions reported in Figure 7 and Figure 8. In figures (a-c), the baseline case is the same as in Figure 7, while a representative error of +10% is assumed for the overestimation curve, and of -10% for the underestimation curve.
Figure 9: Fluid Dynamics instabilities tell about the impact conditions. The number of spines radiating from the edge of a stain increases with the impact velocity (a), from [107]. In (b), [14] shows the dependency of the number of spines on the Weber number. Weber numbers, see Figure 9b.
Figure 9: Fluid Dynamics instabilities tell about the impact conditions. The number of spines radiating from the edge of a stain increases with the impact velocity (a), from [107]. In (b), [14] shows the dependency of the number of spines on the Weber number. Weber numbers, see Figure 9b.
Figure 11: A magnified stain reveals a wealth of features; some of these features, such as cracks in the corona, | are of interest to determine the impact or drying conditions. Images from [156], permission requested. blood had flowed between her breasts and into her clothing.
Figure 11: A magnified stain reveals a wealth of features; some of these features, such as cracks in the corona, | are of interest to determine the impact or drying conditions. Images from [156], permission requested. blood had flowed between her breasts and into her clothing.
Related topics:
GravitationForensic ScienceBloodstain Pattern AnalysisBlood ViscosityDimensionless NumberDroplet Formation
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