基于SPH方法的大块煤冲击破碎数值模拟

为研究大块煤在钎杆冲击下的破碎效果,引入RHT混凝土本构模型材料来模拟大块硬煤（压缩强度35 MPa）,并基于光滑质点流体动力学（SPH）方法建立了钎杆冲击大块煤的三维仿真模型。分析比较了大块在静压、纯冲击和冲压组合作用下的破坏程度,以及平头和圆锥形钎杆冲击效果的差异。仿真结果表明：平头钎杆在30 MPa压力、15 m/s速度或是其组合作用下,均无法使大块产生有效破坏;平头钎杆在200 m/s的超高速下可使大块产生彻体破坏,但实现钎杆高速运动困难;圆锥钎杆在30 MPa压力和15 m/s速度的冲压作用下,使大块产生了较大范围的锥形失效,远高于常规液压破碎锤的单次冲击破坏程度。锥形钎杆、高压高速是破碎硬质大块煤的一种有效方法,可在较少作用次数下实现破碎,验证了低频重载破碎大块的可行性。     

WATER ENTRY OF A WEDGE BASED ON SPH MODEL WITH AN IMPROVED BOUNDARY TREATMENT

The hydrodynamic problem of a two-dimensional wedge entering water is studied based on Smoothed Particle Hydrodynamics (SPH) model. A non-reflection boundary treatment for SPH method is proposed to reduce the reflection of sound waves. The boundary pressure is obtained using an improved coupling boundary treatment approach, which is validated by comparing the simulation results with experimental and analytical results in literature. A series of cases with different initial entering velocities are simulated. The maximum force on the wedge and the corresponding time required to reach it for the different cases of initial entering velocities of the wedge are obained and fitted into formulas against the initial entering velocity of the wedge. The maximum drag coefficients of the wedge for the different cases with Froude number greater than 2 are all near the value of 0.91.     

NUMERICAL SIMULATIONS OF WATER WAVE DYNAMICS BASED ON SPH METHODS

A numerical model was established for simulating water wave dynamic problems by adopting the Smoothed Particle Hydrodynamics (SPH) methods of iterative solution of Poisson's equation for pressure field, and meanwhile the sub-grid turbulence model was applied in the simulation so as to more accurately describe the turbulence characteristics at the time of wave breaking. In this article, simulation of the problem of the dam collapsing verifies the compoting accuracy of this method, and its results can be identical with the results of VOF method and the experimental results by comparison. Numerical simulations of the course of solitary wave and cnoidal wave run-up breaking on beaches were conducted, and the results are basically consistent with experimental results. This indicates that the SPH method is effective for the numerical simulation of the complex problems of water wave dynamics.     

基于SPH方法的油箱抗冲击有限元分析

目的验证SPH方法在流固耦合问题上的适用性。方法采用SPH方法(光滑粒子流体动力学方法)模拟无人机油箱抗冲击过程,并与采用CEL方法(耦合欧拉-拉格朗日方法)模拟得到的结果进行对比。结果 2种模拟方法得到的燃油晃荡情况、油箱应力分布及地面支反力结果接近。结论 SPH方法在流固耦合问题上是适用的。     

基于光滑粒子流体动力学方法的交互式水流加热仿真

针对传统水流加热仿真中交互困难与效率低下的问题,提出一种基于光滑粒子流体动力学(SPH)的热运动仿真方法,旨在交互式控制水流加热变化过程。首先,基于SPH方法将连续水流粒子化,以粒子群模拟水流的运动,并通过碰撞检测方法将粒子运动限定在容器内;然后,采用第一类边界条件的热传导模型加热水粒子,并根据粒子的温度更新粒子的运动状态,以模拟加热过程中水流的热运动;最后,定义可编辑的系统参数与约束关系,通过人机交互仿真多种条件下水流加热及其运动过程。以太阳能热水器加热仿真为例,通过修改少量参数控制热水器的加热工作验证了SPH方法求解热传导问题时的交互性与高效性,为交互式水流加热在其他虚拟场景的应用提供了便利。     

KDP晶体三倍频晶面微观力学行为及加工性能

为了揭示磷酸二氢钾(KDP)晶体三倍频晶面微观弹塑性力学行为及加工性能,开展了纳米压痕研究。建立了KDP晶体三倍频晶面各向异性力学模型,基于光滑粒子流体动力学(SPH)方法对纳米压痕进行了数值仿真并完成了纳米压痕测试实验。实验结果表明:实验与仿真计算的载荷-压入深度关系曲线的相关系数为0.996 328,吻合度较高,验证了力学模型的正确性,得出KDP晶体三倍频晶面的屈服强度为240MPa。数值仿真结果显示:由于材料的各向异性,工件内部应力呈不规则圆弧状分布;载荷大小与等效应力影响深度呈近似线性递增关系;材料表面等效塑性应变分布形状与压头投影面几何形状相类似,存在复映效果。当载荷小于2mN时,各压头的残余应力深度差异性较小(小于0.2μm);随着载荷逐渐增大,这种差异不断扩大。得到的结果为实现KDP晶体三倍频晶面的高效低损伤加工提供了理论支撑。     

Coupling of smoothed particle hydrodynamics and finite element method for impact dynamics simulation

This paper presents an alternative method for coupling smoothed particle hydrodynamics (SPH) and finite element method (FEM) in a Lagrangian framework. The attachment and contact between SPH particles and finite elements are calculated. FE nodes are added to the SPH neighbor list for the attachment, and the continuity of the interface is guaranteed. The contact force on SPH particles and FE nodes is calculated with the same approach used in SPH particle to particle contact algorithm, and the identification of the contact surface and the surface normal is not required. Background particles are assigned in the position of FE nodes to facilitate particle approximation. The perforation of a cylindrical Arne tool steel projectile impacting a plate Weldox 460 E steel target is simulated in 3D to demonstrate the performance of the SPH-FEM coupling algorithm. The coupled computational model of viscoplasticity and ductile damage and Gruneisen EOS are used for the target plate. A particle-kill algorithm is used to invalidate the damage particles. Good agreement between the numerical simulations and the experimental results is obtained, and the ballistic limit velocity obtained from the SPH-FEM coupling algorithm gives a deviation of 2% from the experimental data.     

一个SPH流体实时模拟的全GPU实现框架

怎样实时地进行高度逼真的大规模流体模拟是图形学要研究的一个重要内容。流体的模拟由物理计算、碰撞检测、表面重构和渲染几个部分组成,因此有大量工作针对流体模拟中的各个部分算法进行GPU加速。提出一整套基于GPU的SPH流体模拟加速框架。在利用平滑粒子动力学(SPH)求解Navier-Stokes方程的基础上,借助基于GPU的空间划分PSS(Parallel Spatial Subdivision)来大幅度提升粒子碰撞的检测速度。同时,设计一种基于几何着色器(Geometry Shader)的流体表面信息的重建算法,并进一步地实现基于索引的优化,使得在流体表面重建过程无须遍历不包含表面的区域。实验结果表明,该方法能实时模拟出具有较好真实感的流体场景。     

基于SPH方法的两平行平板间层流的数值模拟及验证

基于SPH方法的基本原理,综合考虑了对各种定解条件的设置,用Fortran语言独立编写了一套用于模拟两平行平板间层流的SPH二维计算程序,并应用于泊肃叶流和库埃特流的数值模拟之中,将模拟结果与理论解析解和通过Flow-3D软件数值模拟得到的数值结果进行对比,分析表明三种方法得到的计算结果非常吻合,从而实现了对SPH数学模型和SPH计算程序的验证,为SPH方法的进一步发展和广泛应用奠定了一定的基础。     

TA2/1060/5083数值模拟及试验

TA2与5083爆炸焊接界面易生成脆性金属间化合物、氧化物、连续熔化区等缺陷,焊接窗口狭窄,最佳焊接参数难以准确获得。本文重构了动态弯折角β和碰撞速度Vf的β-Vf模型,使用SPH-FEM耦合算法,首次运用Steinberg-Guinan材料本构模型进行了炸药厚度为10mm、15mm、20mm,复板厚度为1.5mm的TA2/1060/5083爆炸焊接数值模拟;并采用数值模拟获得的参数开展了爆炸焊接试验。数值模拟和试验结果高度吻合并一致表明：药厚10mm时,TA2/1060和1060/5083界面均呈优质平直状结合,药厚15mm时,1060/5083界面呈波状形貌结合,两种药厚条件下的钛-铝过渡界面均未检测到脆性金属间化合物缺陷生成;药厚20mm时,基复板材料发生破坏,不能实现复合。运用计算优化的参数成功制备了大面积TA2/1060/5083复合材料,本文为理化性能差异较大异种金属等爆炸复合问题提供了一种新的可靠算法。