Final distribution of the sonic Mach number of the hot bubble for different values of (ΔA/A)_t=0 and different grid resolutions. Each panel is rescaled by the corresponding value of . The insets show the maximum sonic Mach number. An entropy perturbation of (ΔA/A)_t=0 = 0.1 drives flows that are far from the low-Mach-number regime. In this case, effects of compressibility caused by the high ram pressure of the bubble are large enough to cause a 6–7% deviation from the theoretical scaling discussed in Sect. 5.4.