Evolution of shock-induced reactive and inert double-layer gas cylinders

The evolution and mixing of shock-induced reactive and inert double-layer gas cylinders are numerically investigated, with inner-to-outer radius ratios ( λ ) ranging from 0.25 to 0.75. In reactive cases, a hot spot forms near the downstream interface of the outer cylinder due to high pressure and temperature from the triple point. When λ increases to 0.75, a second hot spot appears near the upstream interface of the inner cylinder. The distribution of pressure, temperature, and hydrogen mass fraction at the reaction front indicates that deflagration-to-detonation occurs after the generation of the first hot spot. Following the second hot spot, a detonation wave propagates upstream towards the outer interface. Intense heat release following ignition causes an expansion in the outer diameter and the area of the gas ring, while compressing the inner diameter and inner gas area. Detonation results in a more rapid increase in combustion completeness compared to deflagration. Regarding vorticity and mixing fraction, the magnitude of net vorticity decreases, and its rate of decrease slows after ignition as the radius ratio increases. Additionally, the mixing fraction between the mixture in the gas ring and the ambient gas increases with increasing radius ratios in both reactive and inert gas cylinders but remains lower in reactive cylinders compared to inert ones after ignition. • The evolution of shock-induced double-layer gas cylinders is investigated with varying inner-to-outer radius ratios. • A second hot spot appears near the upstream interface of the inner cylinder for larger radius ratios. • The mixing fraction between the mixture in the gas ring and the ambient gas increases with increasing radius ratios.