Initial-amplitude dependence of strong-shock-driven interfacial instability in reflected-shock configurations

Shock-tube experiments are conducted to examine the initial-amplitude dependence of strong-shock-driven interfacial instability in reflected-shock configurations at Mach numbers ( upper M Subscript s M s Mₛ ) exceeding 3.0. Qualitative observations reveal a marked suppression (enhancement) of bubble (spike) growth under strong shocks, with stronger effects at higher dimensionless initial amplitudes ( k a 0 k a 0 ka₀ ). The initial-amplitude effect on linear growth exhibits a non-monotonic dependence on upper M Subscript s M s Mₛ , contrary to the previously anticipated saturation behaviour, arising from the upper M Subscript s M s Mₛ dependence of compressibility and vorticity-deposition contributions. Compressibility suppresses bubble growth via a shock-proximity mechanism while promoting spike evolution through a newly identified Mach-reflection mechanism, with their competition yielding a saturation dependence on upper M Subscript s M s Mₛ . In contrast, the effectiveness of vorticity deposition is modulated by the Mach-reflection structure, with reduced contributions at high upper M Subscript s M s Mₛ due to geometric separation. Based on these insights, an empirical factor is proposed to quantify the initial-amplitude effect across a wide range of k a 0 k a 0 ka₀ and upper M Subscript s