## 2 Materials and Methods
### Spray Parameters, Experimental Design and Settings Used During Trials  
Three different liquid flow rates (LFRs) were investigated, namely 1.00, 1.64 and 2.67 L min\({}^{-1}\). The intended LFR were obtained setting the liquid circuit pressure at 0.1 MPa and using the liquid flow regulator disc (a plastic disc with calibrated holes in its perimeter) in positions 3, 5 and 7, respectively (Table 1). As mentioned above, four HPs were tested in both pneumatic nozzle types, namely CP, AP, OP and XP (Table 1). The intended exact positions of liquid hose, relative to the spout, were guaranteed thanks to a support integral with the spout body (Figure 3a). Concurrently, four AS were tested, namely  
Figure 3: (**a**) Malvern Spraytech® laser diffraction system STP5342 for the measurements of droplet size spectra and (**b**) Testo 400 Pitot-tube-based anemometer for the measurements of airflow speed generated by both cannon-type and hand-type spouts. 81.3, 90.0, 100.2 and 109.2 m s\({}^{-1}\) for the cannon-type nozzle and 57.9, 64.6, 74.3 and 84.2 m s\({}^{-1}\) for the hand-type nozzle. The tested AS values were referred to the reference position (CP), since the increase in spout section diameter deeply affects the decrease of AS along the spout body [55]. The intended AS were obtained properly setting the test bench fan rotary speed to simulate real conditions during spray application. Therefore, the main complexity was to adjust the test bench to make sure it matched the working parameters present in a real sprayer. There are many pneumatic circuit parameters that could be compared in both the bench and the sprayer, but the most representative and the one that ensures an equivalency in the working conditions is the air pressure. Thus, air pressure measurements were done to adjust both systems for every kind of pneumatic nozzle. The fully explained details of the calibration for both cannon- and hand-type nozzles along with the calibration results can be found in [PERSON] et al. [53] and [PERSON] et al. [55]. The air pressure measurements were performed with a manometer with a measurement resolution of \(\pm 1\) mm H\({}_{2}\)O, which was attached to a plastic piece fixed to the nozzle in every case. These pieces were large enough to reach the central part of both air spouts. The air pressure was measured for different Power Take Off (PTO) speed values in order to match the intended AS values previously measured in the real sprayer. According to those measurements, for laboratory trials the test bench fan rotary speeds were set at 541, 598, 663 and 720 rev min\({}^{-1}\) for the cannon-type nozzle and at 488, 536, 609 and 677 rev min\({}^{-1}\) for the hand-type nozzle, respectively. The operating parameters assessed are listed in Table 1.  
The experimental design was completely randomized, as no restrictions were present when measuring the droplet parameters (D50, D10, D90, RSF and V100) for a given combination of values of the independent variables (HP, LFR and AS; Table 1) in each studied pneumatic nozzle. The treatment order was randomized to avoid possible influence of external factors not considered in the design. The dependent variables were the droplet size parameters (i.e., D50, D10 and D90), the droplet homogeneity, given by the RSF, and the droplet driftability, given by the V100 parameter. The trial began with the air spout placement, and it was conducted in two steps. In the first one, the airflow rate was established by adjusting the fan's rotary speed to the values obtained in the calibration [53; 55]. The air speed was then measured in different positions using the Pitot tube, as described before. In the second step, the spray was enabled, and a 30 s time was given to the system to stabilize. Once the time had passed, the laser diffraction instrument was settled at the most appropriate distance from the spout (50 cm in accordance to previous trials [55]), and a total of 30 measurements were taken at 1 Hz acquisition frequency.