# The Impact of Single- and Multicomponent Liquid Drops on a Heated Wall: Child Droplets
## 2 Experimental Procedures
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Composition** & **Water** & **Water** & **Water** \\ \hline No. of impingement & 1 & 2 & 546 \\ \(\alpha_{\text{d}}\)—impingement angle [\({}^{\circ}\)] & 91.2 & 89.4 &... & 30.1 \\ \(R_{\text{d}}\)—drop radius [mm] & 2.5 & 2.2 &... & 2.6 \\ \(U_{\text{d}}\)—drop velocity [m/s] & 1.3 & 2.3 &... & 2.6 \\ Impact outcome & spreading & breakup &... & breakup \\ No. of frame & 54 & 126 &... & 14568 \\ Drop shape & sphere & sphere &... & sphere \\ \(N\)—number of child droplets & 1 & 50 &... & 13 \\ \(\text{We}\)[(2\text{-}R_{\text{d}}\text{-}U_{\text{d}}\text{-}2)/\sigma\) & 126.3 & 341.7 &... & 508 \\ \(\text{Oh}\)-[\(\mu\)/(\(\rho\text{-}2\text{-}R_{\text{d}}\text{-}U_{\text{d}}\))\(\mu\) & 0.0013 & 0.0015 & 0.0013 \\ \(\text{Re}\) [(\(\rho\text{-}2\text{-}R_{\text{d}}\text{-}U_{\text{d}}\))\(\mu\) & 6776.9 & 10,433.5 &... & 13,867.8 \\ \(\beta\)-[\(\text{cos}(\text{d}_{\text{d}})\)] & 0.02 & 0.01 &... & 0.87 \\ \(r_{\text{d}}\)a—mean diameter of child droplets & – & 0.05 &... & 0.23 \\ \(S_{0}\)—surface area of the parent drop [mm\({}^{2}\)] & 79.1 & 66.3 &... & 85.6 \\ \(S_{\text{f}}\)—surface area of the liquid film [mm\({}^{2}\)] & 79.1 & 57.6 &... & 76.4 \\ \(S\)—surface area of child droplets [mm\({}^{2}\)] & – & 105.3 &... & 121.3 \\ \(S_{1}\)—total surface area of child droplets and liquid film [mm\({}^{2}\)] & 79.1 & 162.9 &... & 197.7 \\ \(S_{1}\)/\(S_{0}\) & 1 & 2.4 &... & 2.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Recorded and calculated parameters of the drop impact. The uniqueness of the study as compared to [1; 2; 3; 4; 5; 6; 7; 8; 9; 10] is in studying the effect of different types and characteristics of a surface on drop impact parameters and outcomes. Figure 1 demonstrates how we computed the main parameters. When processing the videos, we determined the angular parameter of \(\beta=\cos(\alpha_{\rm d})\). The variation of \(\alpha_{\rm d}\) results from the inclination of the substrate fixed on a roller at the end of a rod. By using a power-driven position control system and a video camera, the surface slope was adjusted and monitored. In addition, the dimensionless criteria listed in Table 2, namely, the Weber, Ohnesorge, and Reynolds numbers, were calculated. The initial surface area of a drop before impact \(S_{0}\) was given by \(S_{0}=4\cdot\pi{\cdot}{R_{\rm d}}^{2}\) and the volume of such a drop, by \(V_{0}=4/3\cdot\pi{\cdot}{R_{\rm d}}^{3}\). The surface area and volumes of child droplets were given by \(S_{\rm i}=4\cdot\pi{\cdot}{r_{i}}^{2}\) and \(V_{\rm i}=4/3\cdot\pi{\cdot}{r_{i}}^{3}\), respectively. A total surface area of the child droplets \(S\) and their total volume were expressed as a sum of the surface areas of all child droplets and their volumes, respectively. During drop impact, a corona was formed and then broke up. However, the corona disintegrated partially to form a liquid film on the surface. To account for that, the computation procedure was as follows. The liquid film volume was taken as \(V_{\rm f}=V_{0}-V\). After that, we calculated the liquid film area as \(S_{\rm f}=4\cdot\pi{\cdot}{R_{\rm f}}^{2}\), where \(R_{\rm f}\) is the liquid film radius derived from the known volume \(V_{\rm f}\). The cumulative surface area was a sum of surface areas of the child droplets and the liquid film, i.e. \(S_{1}=S+S_{\rm f}\). In this case, the maximum size of the child droplets \(r_{d}^{m}\) corresponded to the radius of the largest secondary droplet and the minimum one to the smallest child droplet size. The mean size of the child droplets \(r_{d}^{a}\) represented the ratio of a sum of the child droplet sizes to their number, i.e., \(r_{d}^{a}=\sum r_{i}/\rm n\).