Dynamics of shock accelerated membraneless gas bubble induced by laser ablation on carbon particle

• Main Authors: Dong-Kai Chen, 陳東楷
• Other Authors: Hong-Yu Chu
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/46414411461169043961

碩士 === 國立中正大學 === 物理學系暨研究所 === 101 === Two gas bubbles are produced simutaneously with a moderate separation by laser induced ablation on micron-sized carbon particles suspended in 460 torr N2 environment. Each gas bubble is produced with the generation of a shock shell. The pressures p of the shock front at differet distances d are measured, and p is shown to decay following p ∼ d^-3 as the shock shell propagates outward, which agrees the theory of shock wave. The evolution of a single gas bubble is presented. The effect of self-acting behavior on the single bubble is neglected due to the differnt time scale with that of two bubbles interaction. In the case of two bubbles interaction, the p-d diagram is used to estimate the pressure of the shock front as the shock shell enters the gas bubble. This shock pressure is compared with the estimation from the speed of shock shell, which shows that the intensity of the shock shell hardly decreases by collision under the present explosion energy. During the evolution of two bubbles interaction, the small-scale fluctuations are observed on the compressed surface of the gas bubble after the shock shell-gas bubble collision. The growth rate of the fluctuations is measured to be linear and is shown to agree with the theory of RM instability. As the alignment of the bubbles is rotated slightly in horizontal plane, the ”fluctuating surface” is observed, which represents the 3D structure of RM instability. A surprising phenomenon is observed that there is a density drop at the intersection of the shock shells, and it lasts for a long time. The possible mechanism is due to the overlapping of the rarefaction waves.