## 3 Results and Discussion
### Discussion  
TEMA tracks the water front position with time and provides the evolution of the velocity with respect to time, which can be straightforwardly processed together with the images to obtain the evolution of the velocity with respect to the distance traveled by the front of water. For the set of 16 tests, the velocity curves versus distance are represented in Figure 9. In the velocity curves, we observe, first of all, descending velocity with distance, as would be expected as the water front increases in size. It is difficult to draw conclusions from the tangle of curves, until they are depicted in colors grouped according to the cylinder diameter and mass of explosive, following Table 2: blue for 86 mm and 40 g/m, respectively; black for 86 mm and 20 g/m; red for 105 mm and 40 g/m; and grey for 105 mm and 20 g/m. In such a way, we can qualitatively observe that the curves are somewhat grouped according to these two parameters. However, in order to quantitatively assess the importance of these factors, a statistical analysis must be performed. Figure 8: Image of test 1. A radial disk of water and water projected vertically upwards. Figure 7: Images of test 1 taken by the high-speed camera at 6000 fps. (**a**) Device prepared for detonation; (**b**) detonator explosion; (**c**) upper dark cloud formed by gases produced by the detonating cord; (**d**) disk of water projected by the effect of the explosion. Taking into account that the factor related to the position of the IED, as explained in Section 2.2.4, is the distance from the cylinder to the IED, it is necessary to obtain the value of the water velocity for a distance of 40 cm or 55 cm, depending on Table 2. These values are interpolated in the curves from Figure 9. Results are presented in Table 4.  
For data analysis, Minitab17 is used [25]. In order to observe the influence of the factors and interactions (model terms) and the probability of randomness in their influence on the response, an ANOVA test is carried out. It should be borne in mind that, if all the terms of the model are included (all factors and interactions), the degree of freedom \(D_{f}\) of the residual error is 0 (the model is saturated) and no data are obtained in relation to the \(F\)-value or \(p\)-value [25]:  
\[D_{f(residual\ error)}=D_{f(Model)}-\sum D_{f(factors\ and\ interactions)}=15-15=0 \tag{3}\]  
If the \(D_{f}\) of the residual error is 0, then the Mean Squared Error (MSE), which, by definition, is \(MSE=SS_{(residual\ error)}/D_{f(residual\ error)}\), cannot be calculated. In turn, it is impossible to calculate the \(F\)-value of each of the terms given that  
\[F_{term}=\frac{\text{Term\ mean\ square}}{\text{Mean\ square\ of\ residual\ error}}=\frac{MS}{MSE} \tag{4}\]  
Then, to obtain statistical values, a stepwise analysis is applied, starting with an empty model in which the most significant factor or interaction of factors obtained in a previous analysis is incorporated. In this way, we obtain the result shown in Table 5. From the analysis, it is obtained that the \"Explosive Specific Mass\" factor is the most significant because it has the highest \(F\)-value (\(F\)-value = 139.97), followed by \"Diameter\" (\(F\)-value = 39.85), and by the interaction of \"Explosive Specific Mass\" and \"Density\" (\(F\)-value = 6.02), the interaction of \"Diameter\" and \"Inner Tube\" (\(F\)-value = 4.46), \"Density\" (\(F\)-value = 0.44), and, finally, by the \"Inner Tube\" (\(F\)-value = 0.23). Furthermore, the factor \"Distance\" is discarded because the purpose is to identify a useful subset of terms [25]. The fact that the distance between 40 and 55 cm is not significant is a positive conclusion of the study, because this indicates that the operator does not need to be concerned when placing the