## 3 Results and Discussion
### Experimental Results  
Figures 9-12 show the results of the experimental investigation of the streamlined body cooling process and velocity change. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Body** & **Water** & **Body** & **Steam Mass** & **Drag Force** & **Drag** \\
**Velocity, m/s** & **Temperature,**\({}^{\circ}\)C & **Temperature,**\({}^{\circ}\)C & **Fraction,**\(\omega_{i}\) & **\(D,\mathbf{N}\)** & **Coefficient**\(C_{D}\) \\ \hline
0.5 & 98 & 98 & 0 & 0.0184 & 0.417 \\
0.5 & 98 & 150 & 0.004 & 0.0125 & 0.283 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Modeling results of the streamlined body. Figure 8: Drag force distribution for the cold (**a**) and hot (**b**) streamlined bodies at 0.5 m/s. Figure 11: Film boiling (**a**) change to nucleate boiling (**b**). Figure 10: Streamlined hot body positions in different parts of the experimental channel. Figure 9: Dynamics of the cooling process of the streamlined body: A—slow cooling in air, B—initial contact with water; C—full immersion in water and film boiling; D—nucleate boiling. Figure 9 shows the dynamics of the cooling process of the motionless streamlined body in water, the temperature of which was close to the saturation temperature (98 \({}^{\circ}\)C). Motionless streamlined body was cooled down from 410 \({}^{\circ}\)C to 98 \({}^{\circ}\)C within 25 s. The investigation showed that the film boiling regime was fully changed by the nucleate boiling regime after 12 s. Meanwhile, for the moving streamlined body, the falling time in water channel was less than 2 s for all the experiments (water column height 1.5 m); therefore, film boiling regime was observed along the entire path of the falling body. Nucleate boiling regime started at the body surface temperature equal to 190 \({}^{\circ}\)C.  
Figure 10 shows different positions of the hot streamlined body (150 \({}^{\circ}\)C) falling in the experimental channel filled with water (98 \({}^{\circ}\)C). Intensive steam generation can be noticed at the tail part of the body. Front part of the body was cooled faster due to its permanent contact with the flow of water. Consequently, steam generation occurred here only during the first phase of the contact between the streamlined body and water. The remaining part of the body was in contact with water at a temperature higher than the temperature of main flow due to water heating on the front part of the body. Therefore, steam generation was more intensive and lasted longer at that area. Figure 11 demonstrates film boiling regime alteration to the nucleate boiling regime. The initial temperature of the streamlined body was 410 \({}^{\circ}\)C; water temperature was close to the saturation temperature (98 \({}^{\circ}\)C). Film boiling transition to nucleate boiling started at the front part of the body because of the better cooling by the colder water flow contacting the respective part of the body. Figure 12 demonstrates the streamlined body velocity dependence on the falling time. Due to limitations of the ANSYS CFX program package, the experiments were performed at the body temperature equal to 150 \({}^{\circ}\)C and water temperature equal to 98 \({}^{\circ}\)C. Such temperatures corresponded to the nucleate boiling regime (Figure 9). Sufficient increase of the body velocity was noticed despite the small amount of vapor generated on the body surface. Solid line and rectangular dots represent the results of the simulation and experimental data correspondingly for the cold body fall in the channel of water (98 \({}^{\circ}\)C). Round dots and the dotted line show the experimental data and results of simulation for the hot (150 \({}^{\circ}\)C) body falling in water, the temperature of which was 98 \({}^{\circ}\)C. Coincidence of the experimental data and the results of simulation were quite good; discrepancy was less than 10%. It can be noticed that velocity difference was very small for the cold and hot bodies at the initial moment of the fall; however, it reached 20% and more after 0.3 s of the falling process.