**5. Experimental results**

136 Thermodynamics – Interaction Studies – Solids, Liquids and Gases

parameters are the laser power, duration of the laser pulse, and diameter of the cell exit hole. We therefore assume that the experimental parameters related to the laser power and pulse correspond to the jet Mach number and jet duration, respectively. Hence, we have selected the above three parameters to be tested, fixing all the other parameters. The states of the gas inside and outside of the cell are initially at rest, that is, the ambient properties such as the pressure, density, temperature are uniform over the whole calculation region.

Fig. 7. Time variations of density contours in the ellipsoidal cell.

Figures 7(a) to (f) show the calculated density fields using certain parameters. As illustrated in the previous section, a shock wave was generated by the sudden expansion of the ejected plume in the ellipsoidal cell. Together with the plume jet, the shock wave propagated towards the right wall of the cell. The plume has decelerated while the shock wave continues to move towards the exit hole (Figure 7(a)). The distance between the plume front and the shock wave increased. The propagating shock wave was reflected from the upper wall of the cell and changed direction toward the focal point. The propagating shock wave arrived at the exit hole and was reflected from the cell wall (Figure 7(b)). The shock wave behind the plume started to interact with the plume front. Figure 7(c) shows the moment when the shock wave was focused at the focal point of the cell and, at the same time, the plume front was located at almost the same point. The plume seems to be blocked by the converging shock wave. Namely, it was recognized that a confinement of the plume was occurred at the time. The transmitted shock wave through the exit hole is so weak that the density contour fields outside of the cell cannot be seen. After the shock wave has

**4.3 Shock wave behavior and interaction with plume** 
