Based on the three-dimensional SPH methodi the variable smoothing length modification is applied to the traditional linked-list search algorithm, and the stable approach of dealing with multiphase material interface is put forward. Through simulating underwater explosion of free field, the feasibility and effectiveness of the modified method are verified. The three-dimensional numerical model is established, and the process of underwater explosion near free surface is reproduced. Characteristics of shock wave propagation, pressure field and energy field are summed up. The effect of different explosion depth on the initial water column formation is studied. Results show that free surface can attenuate the peak pressure and impulse to one third and one seventh of the original values, respectively. With the increase of detonation depth, curvature of the equivalent cylinder of peak pressure ratio and impulse ratio decrease, and the produced water column gradually transits from broken and spray column to high and narrow mound.%基于三维SPH方法,对传统链表搜索算法进行了变光滑长度改进,并提出了具有较好稳定性的多相物质交界面的处理方法,模拟了三维无限域水下爆炸问题,验证了改进的三维SPH方法模拟水下爆炸问题的可行性和有效性.在此基础上,建立了水下爆炸三维数值模型,模拟了近自由面水下爆炸过程,研究了冲击波传播特征、自由面下压力场和能量场特性以及水柱的产生过程.结果表明:自由面可将冲击波压力峰值和压力冲量最大衰减到1/3和1/7;爆深的增加会导致压力比和冲量比的等值柱面曲率变小,产生的水柱也逐渐由破碎的喷柱向高而窄的水冢过渡.
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