## 5 Results
### Comparison with Human Vapers
#### 5.3.1 DTL Vaping  
The evolution of a vaping jet/puff system for a vapor following the DTL style can be appreciated in the sequence of frames displayed in Figure 3. While this style is followed by a minority of vapers (see Section 2.1.2), its large volume of exhaled air and ECA and large distance spread make it suitable to illustrate the evolution of the jet/puff system associated with vaping. Figure 3 contains five images corresponding to the stages of jet/puff formation and evolution in a sequence given by the following time frames from top to bottom (the filmed sequence is available in Supplementary Material SM(3))  
First FrameThe starting jet thrusted by the linear momentum of the exhalation has a rough conical shape with dispersion angle comparable to \(\alpha\sim 15\,^{\circ}\), as described in Section 5.2 and depicted in Figure 1.  
Second FrameAs more ECA and exhaled air are injected, the shape of the frontal development of the starting jet becomes deformed by entrainment of surrounding air, which initiates the formation of a turbulent vortex. The jet areas close to the injection source (vaper's mouth) remains close to the initial conical shape.  
Third FrameEntrainment from surrounding air generates more turbulent mixing, giving rise to the slow formation of a puff as a deformed ellipsoidal shape that slowly separates from the fully developed stating jet, since fluid and ECA injection continues.  
Fourth FrameAs the injection wanes, the starting jet weakens, gradually losing its straight conical shape. The puff becomes fully developed and evolves forward, giving rise to more air entrainment and turbulent mixing.  
Fifth FrameAs injection stops, the starting jet is gone and the puff structure begins to disperse.  
As shown by the frames depicted in Figure 3 and in the video from where this sequence was taken (see video DTL1 in SM(3)), the simple hydrodynamical model presented and discussed in Sections 4 and 5.2 provides a reasonably good approximation to real life vaping, at least up the fourth frame before the final dispersion of the puff when injection ends (this is also true for MTL vaping with a tank device as we show further ahead). Evidently, the horizontally thrusted jet/puff system generated by this vapor (following DTL vaping style) reaches over 2 m of horizontal displacement, which up the puff dispersion final stage remains quite directionally collimated. This corresponds to the upper displacement curves in Figure 2, indicating a probable exhalation velocity of \(U_{0}\sim 4\)-5 m/s and total fluid injection of over 2 L. However, not all vapers doing DTL style thrust the jet/puff system such large distance spreads and injected fluid volumes, since these parameters should also depend on the lung capacity of the vapor, which varies in direct proportion to body size. The vapor of Figure 3 has a large lung capacity, as he is 1.86 m tall and weighs 110 kg. In the video DTL2 in SM(3), his vaping exhalation is compared to that of a vapor 1.70 m tall weighing 74 kg, whose jet/puff system has a much shorter spread barely surpassing 1.5 m, corresponding (from the results in Figure 2) to probable exhalation velocity \(U_{0}\sim 2.5\,\) m/s and total fluid injection of 1.5 L.  
Figure 3: Formation and evolution of the vaping jet/puff system. The images denote from top to bottom a sequence of time frames of a vaping jet/puff system associated with the intense DTL style. Each frame is explained in the main text. The video footage is available in SM(3)