FP-1装置铝套筒内爆动力学过程的一维磁流体力学模拟

作为一种重要的柱面会聚冲击和准等熵压缩加载源,磁驱动固体套筒内爆技术已广泛应用于高能量密度物理实验研究.针对FP-1装置驱动的固体套筒内爆动力学过程,建立了含强度的一维磁流体力学模型,并对典型实验进行了模拟.计算获得的套筒内爆速度同实验结果较为相符.模拟结果显示,该装置在40 kV充压条件下,可以将直径3 cm,厚0.5 mm的铝套筒加速至1.1 km/s,内壁速度超过1.5 km/s,同时保持大部分材料为固体状态.内爆套筒与相同材料靶筒碰撞产生的冲击压力约9 GPa.改变靶筒内部填充气体的压力,可以获得不同的靶筒运动速度、轨迹以及反弹半径,以满足不同类型实验的研究需要.     

Modernization and optimization of a legacy open-source CFD code for high-performance computing architectures

Legacy codes remain a crucial element of today's simulation-based engineering ecosystem due to the extensive validation process and investment in such software. The rapid evolution of high-performance computing architectures necessitates the modernization of these codes. One approach to modernization is a complete overhaul of the code. However, this could require extensive investments, such as rewriting in modern languages, new data constructs, etc., which will necessitate systematic verification and validation to re-establish the credibility of the computational models. The current study advocates using a more incremental approach and is a culmination of several modernization efforts of the legacy code MFIX, which is an open-source computational fluid dynamics code that has evolved over several decades, widely used in multiphase flows and still being developed by the National Energy Technology Laboratory. Two different modernization approaches,‘bottom-up’ and ‘top-down’, are illustrated. Preliminary results show up to 8.5x improvement at the selected kernel level with the first approach, and up to 50% improvement in total simulated time with the latter were achieved for the demonstration cases and target HPC systems employed.     

杆式射流对充液防护结构的毁伤机理及影响因素的数值模拟

运用ANSYS/LS_DYNA软件分析了聚能射流对充液结构的毁伤,初步获得了药型罩壁厚和材料等参数对聚能战斗部水下作用的影响特性。药型罩壁厚在0.04D_k~0.06D_k(D_k为装药直径)之间形成的射流对充液防护结构具有较优的侵彻性能;当δ<0.04D_k时,杆流成型结构较差,在水中的动能抗衰减性能较低;δ>0.06D_k时,射流的初始动能低,靶后效果差。药型罩可采用纯铁、紫铜和钽3种材料,其中纯铁射流的侵彻能力最高,钽射流在水中的动能抗衰减性能最好,紫铜射流具有较好的综合性能。     

磁化套筒惯性聚变典型物理过程及特征参量

磁化套筒惯性聚变(MagLIF)结合了传统磁约束聚变(MCF)与惯性约束聚变(ICF)的优势,理论上在有限的驱动能力下可以有效降低聚变实现的难度,具有极大的应用潜力。基于一维集成化物理模型编写了数值模拟程序,以ZR装置典型驱动能力27 MA为出发点,以时间演化为顺序,通过数值模拟系统性地总结分析了典型负载参数下MagLIF构型初始化、加速内爆及迟滞3个关键过程中重要特征参量的分布及演化情况。数值模拟结果有助于理解MagLIF构型从预加热经由燃料压缩到最终发生聚变这一快速而复杂的过程,从而为建立相应的物理图像和认知提供了重要支撑,与传统ICF典型参数的对比也体现了该构型的优势所在,为后续研究奠定了基础。     

A modified saddle point method for predicting sound fields above a non-locally reacting porous medium

This paper examines an asymptotic analysis for predicting sound fields above a rigid-frame porous medium, the so-called non-locally reacting porous medium. Their solutions can be represented by a direct wave term, a reflected wave term and a diffraction wave term. Exact and analytical solutions are available for the direct wave and the reflected wave from a perfectly hard ground. In the contrary, the diffraction wave term can only be cast in an integral form that is amenable to approximate analysis. A modified saddle-point method is explored to evaluate the diffraction integral asymptotically. Three different types of non-locally reacting surfaces, which are an extended reaction, a hard-backed layer, and an impedance-backed layer, were considered. The sound fields above these porous surfaces have the same form but they are different by an augmented diffraction term in the solutions. The analytical formula for the total sound fields, which can be stated in a closed form, offer a physically interpretable solution comprising of a direct wave and ground reflected wave terms. This latter term can further be split into a specularly reflected plane wave and ground wave components. A series of numerical comparisons have been conducted to validate the asymptotic analyses presented in this study. It has been demonstrated that the overall sound fields can be predicted well by the formula for all incidence angles and for a wide range of non-locally reacting porous surfaces.     

一种形成尾翼型聚能侵彻体新方法的实验研究

尾翼可以提高聚能侵彻体的飞行稳定性,如何形成有一定规律性的尾翼在聚能侵彻体的研究中具有重要意义。在药型罩上粘附隔板,利用隔板改变爆轰波波阵面的结构形状,使药型罩上的爆轰压力发生规律变化,从而发生规律性的变形,最终形成带有尾翼的聚能侵彻体,这是一种新的形成尾翼的方法。从药型罩微元压垮速度变化和药型罩表面爆轰压力变化的角度出发,对新方法形成尾翼的机理进行了初步探讨。通过合理设计隔板的几何尺寸对该方法形成尾翼型聚能侵彻体进行试验,试验回收到了带有尾翼的聚能侵彻体,说明新方法形成尾翼具有一定的可行性。     

随机模拟化学反应系统的加速L-leap算法

提出了随机模拟化学反应系统的加速L-leap算法,该算法根据leap条件确定具有最大倾向函数的反应通道的反应次数,并利用二项分布随机数生成其它反应通道在当前leap时间区间内的反应次数．L-leap算法可更好地满足leap条件．数值模拟实验表明该算法能取得更好的模拟性能．     

General decay of solutions of a wave equation with memory term and acoustic boundary condition

In this paper, the global solvability to the mixed problem involving the wave equation with memory term and acoustic boundary conditions for non‐locally reacting boundary is considered. Moreover, the general decay of the energy functionality is established by the techniques of Messaoudi. Copyright © 2016 John Wiley & Sons, Ltd.     

Numerical simulation of supersonic reacting mixing layer

In this paper, the supersonic chemically reacting mixing layer is simulated with the third order ENN scheme, based on the Navier-Stokes equations, containing transport equations of all species. The numerical results show that the thickness of mixing layer increases gradually along the flow direction, and that the Kelvin-Helmholtz instabilities may not exist in mixing layer flows. The project supported by the National Natural Science Foundation of China