基于ALE算法的单孔台阶爆破数值模拟研究

岩石在炸药爆炸荷载作用下,其瞬态破坏过程难以用现有的技术进行有效的监测。为研究在台阶爆破中岩石的破碎及抛掷过程,采用LS-DYNA建立单孔台阶爆破三维数值计算模型,通过ALE算法并结合流固耦合定义岩石和炸药的接触,模拟炸药在炮孔内爆炸的全过程。分析了炮孔内炸药的爆轰过程及其压力极值分布、岩石裂纹的形成和拓展的宏观现象、岩石的块度分布及其抛掷过程。模拟计算结果显示,炮孔粉碎区半径为装药半径的3.9倍,坡面破碎岩石的最大抛掷速度为73.8m/s。采用ALE法模拟单孔台阶爆破,其爆破效果与现有工程实际相吻合,可以为工程爆破参数的设计和优化提供参考。     

Modeling of shear localization during confined granular flow in silos within non-local hypoplasticity

The paper deals with multiple shear zones in the interior of cohesionless granular bodies during plane strain quasi-static granular flow with controlled outlet velocity in experimental silos. The finite element calculations were carried out with a hypoplastic constitutive model enhanced by a characteristic length of micro-structure by means of a non-local theory to obtain mesh-independent results. The constitutive model can reproduce the essential features of granular materials during shear localization. FE analyses were performed with the help of an Arbitrary Lagrangian-Eulerian formulation using an explicit time integration approach for experimental silos containing initially dense dry cohesionless sand. Silo walls were assumed to be very rough or smooth. Emphasis was given to the propagation of multiple shear zones in the interior of flowing sand. The numerical results were compared with corresponding experimental tests.     

ALE有限元方法在金属塑性加工中的应用

ALE (ArbitraryLagrangian Eulerian)有限元方法中 ,网格划分是在参考构形中进行的 ,网格独立于物体和空间运动 ,可以根据需要自由选取。因此 ,ALE有限元避免了La grangian有限元中的网格畸变 ,又克服了Eulerian有限元中难以描述自由边界的不足。对ALE有限元用于分析塑性加工过程进行了探讨 ,并利用Galerkin方法 ,推导了离散形式的求解方程。最后的数值算例验证了该算法的有效性。     

海上风电厚壁筒型基础刃脚优化试验及下沉阻力研究

通过在筒裙端部加装刃脚进行减阻,并通过试验寻找最优的刃脚体型,同时利用任意拉格朗日欧拉方法（ALE）进行筒型基础下沉全过程数值模拟。结果表明：在厚壁筒型基础端部加装刃脚可有效减小端阻力,在砂土中下沉时,最优的刃脚体型为60°夹角,通过试验对比,证明理论公式计算端部压力的可行性;ALE数值方法可模拟试验模型下沉过程,误差在20%以内。最后,利用ALE数值模拟,分析刃脚端面和斜面应力分布,并且研究土质参数对刃脚结构下沉阻力的影响。     

Simultaneous Heat and Mass Transfer in Shrinkable Apple Slab During Drying

The goal of the study was to determine the influence of drying shrinkage on the kinetics of convection apple slab drying. The arbitrary Lagrange-Eulerian (ALE) method was used to enter a problem with moving boundaries. It was found that drying shrinkage had a major influence on the both simulated temperature and water content in the material. The lower the moisture content in particles during drying, the more pronounced the effect of shrinkage on simulation of heat and mass transfer. It was found that application of the arbitrary Lagrange-Eulerian method for shrinkage modeling leads to a relatively simple mathematical model of the drying kinetics of shrinkable materials.     

Efficient and accurate approach for powder compaction problems

 In this paper, a new approach for powder cold compaction simulations is presented. A density-dependent plastic model within the framework of finite strain multiplicative hyperelastoplasticity is used to describe the highly nonlinear material behaviour; the Coulomb dry friction model is used to capture friction effects at die-powder contact; and an Arbitrary Lagrangian–Eulerian (ALE) formulation is used to avoid the (usual) excessive distortion of Lagrangian meshes caused by large mass fluxes. Several representative examples, involving structured and unstructured meshes are simulated. The results obtained agree with the experimental data and other numerical results reported in the literature. It is shown that, contrary to other Lagrangian and adaptive h-remeshing approaches recently reported for this type of problems, the present approach verifies the mass conservation principle with very low relative errors (less than 1% in all ALE examples and exactly in the pure Lagrangian examples). Moreover, thanks to the use of an ALE formulation and in contrast with other simulations, the presented density distributions do not present spurious oscillations. Received: 20 March 2002 / Accepted: 15 October 2002 The partial financial support of the Ministerio de Ciencia y Tecnología (grant number DPI 2001-2204) is gratefully acknowledged.     

对碰波作用下金属圆管运动特性的数值模拟

基于LS-DYNA非线性动力有限元程序，利用ALE算法，对两端面同时起爆作用下金属圆管内爆轰波的相互作用效应进行了三维数值模拟，复现了金属圆管对碰区鼓包及对碰部位首先贯穿断裂的现象．与文献结果进行了对比，计算结果与文献实验结果吻合较好，验证了该计算模型和方法的合理性．     

大型U形渡槽动力性能分析

以东深供水改造工程中樟洋渡槽和某小型渡槽为研究对象 ,对比分析大型预应力U形渡槽结构动力特性 ,研究渡槽结构在Mexico强震激励下的振动反应 ,以获得渡槽中动水压力资料。研究表明常规的抗震设计方法可以满足小型渡槽结构的抗震设计要求 ,而大型渡槽中水体的大幅晃动作用较大程度地改变了水压力、槽体应力的分布和数值 ,对渡槽中预应力钢筋不利 ,在渡槽的抗震设计中 ,动水压力应该作为一项主要的外荷载予以考虑。     

A complete finite element treatment for the fully coupled implicit ALE formulation

This paper presents a complete derivation and implementation of the Arbitrary Lagrangian Eulerian (ALE) formulation for the simulation of large deformation quasi-static and dynamic problems. While most of the previous work done on ALE for dynamic applications was mainly based on operator split and explicit calculations, this work derives the quasi-static and dynamic ALE equations using a fully coupled implicit approach. Full expression for the ALE virtual work equations and finite element matrices are given. Time integration relations for the dynamic equations are also derived. Several quasi-static and dynamic large deformation applications are solved and presented.     

On reduced modeling of mass transport in wavy falling films

In many industrial units such as packing columns, falling film reactors, etc., the liquid phase is designed as a falling film. It is well known that the mass and heat transfer in laminar wavy film flows is significantly enhanced compared to flat films. The kinetic phenomena underlying the increase in mass and heat transfer are, however, still not fully understood. For an efficient design of falling film units, computational models that account for these enhanced transport mechanisms are of key importance. In this article, we present a reduced modeling approach based on a long‐wave approximation to the fluid dynamics of the film. Furthermore, we introduce a new two‐dimensional (2D) high‐resolution laser‐induced luminescence measurement technique. Both in the numerical simulation results and in the high‐resolution 2D‐concentration measurements obtained in the experiments we observe similar patterns of high concentrations locally, especially in the areas close to the wave hump. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2265–2276, 2018