Abstract:
The flow instability development of a shock-accelerated saw-tooth interface has been studied in shock tube experiments, and the effect of initial vertex angle on the bubble competition is highlighted. The soap film technique is adopted to generate the initial saw-tooth gaseous interface, and the post-shock flow is captured by a high-speed video camera combined with the schlieren photography. The results show that at the very early stages, the large and small bubbles develop independently, implying that the bubble competition does not work initially. As the time goes by, the bubble competition plays an important role, and behaves differently for the saw-tooth interface with different vertex angles. As the vertex angle reduces, more baroclinic vorticity is deposited with the interface developing more quickly, and the bubble competition occurs earlier and becomes more significant. The bubble competition promotes the large bubble growth, whereas it inhibits the small bubble growth. Relatively, the bubble competition has a more prominent effect on the small bubble growth. Moreover, the bubble competition will distort the spike head, which will affect the total interface amplitude growth. The bubble front difference seems to experience two linear stages before it enters nonlinear stage. The growth rate in the second linear stage is smaller than that in the first linear stage, indicating that the nonlinearity exerts a significant effect to the flow in the second stage. Specifically, the nonlinearity plays a more significant effect on the large bubble growth. The bubble front difference cannot collapse in dimensionless form, which means the vertex angle has a great influence on the saw-tooth interface development.