## 3 Results
From Figure 4a, it can be observed that at the fourth sampling line, the number of droplets with a diameter less than or equal to about 2 microns reaches its peak value. However, the quantity of droplets with \(d_{d}\ \geq 3\) um remains unchanged for droplets of all sizes, unlike the corresponding characteristic depicted in Figure 4b. In the latter case, the number of droplets is significantly higher in value in contrast to the former one. It was observed that the quantities of droplets with all sizes fluctuate, and the maximum value was reached for droplets with diameters of up to about 4 microns. The red lines in Figure 4a,b. correspond to the droplet quantity that was measured at the first sampling line. The green line represents the number of droplets that was measured at the fourth sampling line.The comparison of measurement data (Figure 4a) marked with red and green line, respectively, leads to the conclusion that the droplets with \(d_{d}\ \leq\ 4\) microns must have been separated from the main flow. In addition, it was noticed that the amount of droplets fluctuates nonlinearly and its content at the second sampling line is lower than at the third one. The reason for this is the hydraulic stabilization of the flow. In the area of flow development, the fluid's velocity profile changes, and it fluctuates in both perpendicular and parallel directions to the flow direction. A steady-state velocity profile is achieved after the boundary layer thickness reaches the radius of the pipe at the end of this section of the channel. Figure 4b. introduces an opposite trend, where the mass content of droplets is the highest in value at the fourth sampling line, and the characteristics obtained for other sampling lines vary linearly, unlike Figure 4a. Supplementary characteristics are included in the Appendix C, and the difference in measured values of DSD and DQ between adjacent sampling lines for \(n\) = 5 Hz are depicted in Figure A6. As can be observed in Figure 5, the change in the value of \(Tu\) against the length of the \(SCh_{1}\) channel is nonlinear for fan frequency equal to 4 and 5 Hz. The fan frequency being increased to 6 Hz causes the \(Tu\) volatility along the channel to become linear, as observed. Figure 4: DSD and DQ at four sampling lines for fan frequency: (**a**). \(n\) = 5 Hz and (**b**). \(n\) = 6 Hz. Figure 6 depicts the variation in \(T\!u\) against the fan frequency. The outcomes obtained for the second sampling line acknowledge that nonlinear variation in \(T\!u\) occurs. Correlations of \(T\!u\) with fan frequencies and with the speed of the gas flow are presented in Figures 6 and 7. The assertion that the turbulence factor value always increases as the speed increases is incorrect (Figures 5-7). Figure 5: Variation in turbulence intensity against the length of the \(SCh_{1}\) channel. Figure 6: Turbulence intensity as a function of \(n\). The dependency of the amount of both the airborne and larger droplets (up to about 20 microns) that exist in the core of the flow is influenced by the turbulence intensity. An appropriate correlation is presented in Figures 8-10. Figure 8: Quantity of sub-micron droplets, few-micron droplets, and larger droplets present in the core of the flow against turbulence intensity at \(n~{}=~{}6~{}~{}\mathrm{Hz}\). Figure 7: Turbulence intensity as a function of the mean speed of the airflow. It was noticed that \(Tu\) influences small droplets' presence in the flow (Figures 8 and 10). The impact of \(Tu\) on a droplet separation is also nonlinear (Figures 8 and 9). At low fluid flow speed, the boundary layer is the thickest. Figure 11 presents a correlation of the BL thickness and the maximum speed of the airflow obtained for individual fan frequencies. It was observed that for \(Tu_{max}\), a minimum amount of micron and sub-micron droplets occurred in the flow (\(dN_{min}\)) (Figure 8), though \(Tu_{max}\) was reached at the lowest fan frequency \(n=1\) Hz, which results in the lowest value of the speed of the gas at which the BL is the widest.