水下爆炸作用下基于声学的爆源子结构输入方法

无限域吸收边界和爆炸波输入是水下爆炸载荷数值模拟的两个关键问题.本文借鉴基于内部子结构的地震波动输入方法和爆源子结构多尺度分析方法,考虑水下爆炸载荷与地震载荷同属于波动问题,提出一种水下爆炸作用下爆源子结构的爆炸波输入方法,该方法首先通过对爆源区域进行水下爆炸波自由场的波场分解,并利用地震波的内部子结构输入方法,将该自由波场运动转换为等效爆炸波输入载荷,从而实现了水下爆炸问题中冲击波的输入;本文采用圆形爆源子结构区域,并采用AUTODYN软件中一维自由场模型计算水下爆炸作用下该区域的自由波场压力时程.进一步,基于连分式近似方法提出了一种模拟无限域水体辐射效应的高精度时域人工边界条件,该吸收边界可设置于离结构和爆源子结构较近处.本文提出的分析方法通过圆形爆源子结构进行水下爆炸载荷的转化,并采用高精度吸收边界大大减少计算区域,既保证了计算精度,又降低了单元数量,具有较高的计算效率和较强的实用性.通过数值算例分析,验证了本文模型与方法的准确性,模拟了水下爆炸作用下的冲击波和气泡脉动阶段测点的压力时程曲线,并研究了圆形结构对水下近场爆炸波散射效应的影响规律.

AN INPUT METHOD FOR EXPLOSION PROBLEMS BASED ON THE ACOUSTIC SUBSTRUCTURE OF EXPLOSION SOURCE UNDER UNDERWATER EXPLOSIVE LOADING

The infinite domain absorption boundary and explosion wave input method are two keys of numerical simulation research on underwater explosion. This paper draws on the seismic wave input method based on the internal substructure and the multiscale analysis method for explosion problems based on the substructure of explosion source and proposes a shock wave input method for underwater explosion based on the substructure of explosion source considering that the underwater explosion load and the seismic load belong to the same fluctuation problem. The method first decomposes the shock wave field in the explosion source region and the free wave field motions were transformed into the equivalent explosive loads, which enables the input of shock waves in the underwater explosion problem. In this paper, a circular substructure of explosion source is used, and a one-dimensional model in AUTODYN software is used to calculate the free shock wave pressure in this region under the action of the underwater explosion. Further, based on the continuous fractional approximation method, a high-precision time-domain artificial boundary condition is proposed to simulate the radiation effects of infinite domain, which can be placed close to the structure and explosive source substructure is proposed. The method proposed in this paper transforms the underwater explosion load through the substructure of explosion source and adopts the high accuracy absorption boundary to greatly reduce the calculation area, which not only ensures the calculation accuracy, but also reduces the number of elements, with high calculation efficiency and practicability. Finally the numerical example is analyzed to verify the accuracy of the model and method of this paper, The pressure time history curves of measuring points during shock wave and bubble pulsation stage under underwater explosion are simulated, and the effect of circular structure on the scattering effect of underwater near-field explosion wave is studied.