流-固耦合问题的ALE有限元分析

基于任意Lagrange-Euler描述(ALE),建立了分析流-固耦合问题的预报-更正算法.采用ALE描述下的Galerkin/最小二乘有限元法,完成了对具有运动边界的不可压缩粘性流的数值模拟;并提出基于更新Lagrange列式的伪弹性体法来计算网格运动;通过在耦合界面上对流体和固体分别施加Dirichlet和Neumann边界条件,建立了流-固耦合关系,并数值模拟了流道中与流速垂直的悬臂梁的流-固耦合过程,数值算例的结果验证了本文方法的有效性.     

Combined interface boundary condition method for unsteady fluid–structure interaction

Traditionally, continuity of velocity and traction along interfaces are satisfied through algebraic interface conditions applied in a sequential or staggered fashion. In existing staggered procedures, the numerical treatment of the interface conditions can undermine the stability and accuracy of coupled fluid–structure simulations. This paper presents a new loosely-coupled partitioned procedure for modeling fluid–structure interaction called combined interface boundary condition (CIBC). The procedure relies on a higher-order treatment for improved accuracy and stability of fluid–structure coupling. By utilizing the CIBC technique on the velocity and momentum flux boundary conditions, a staggered coupling procedure can be constructed with similar order of accuracy and stability of standalone computations for either the fluids or structures. The new formulation involves a coupling parameter that adjusts the amount of interfacial traction in the form of acceleration correction, which plays a key role in the stability and accuracy of the coupled simulations. Introduced correction terms for velocity and traction transfer are explicitly added to the standard staggered time-stepping stencils based on the discretized coupling effects. The coupling scheme is demonstrated in the classical 1D closed- and open-domain elastic piston problems, but further work is needed to consider the analytical stability of these schemes, 3D problems and comparison to monolithic integration.     

A numerical method for elastic and viscoelastic dynamic fracture problems in homogeneous and bimaterial systems

We present a summary of recent advances in the development of an efficient numerical scheme to be used in the investigation of a wide range of 2D and 3D dynamic fracture problems. The numerical scheme, which is based on a spectral representation of the boundary integral relations, can be applied to homogeneous and interfacial dynamic fracture problems involving planar cracks and faults of arbitrary shapes buried in elastic and viscoelastic media. Spontaneous propagation of the crack is achieved by combining the elastodynamic integral relations with a stress-based cohesive failure model. The objective of this paper is to present some of the major differences existing between the various formulations within the simpler 2D scalar framework of anti-plane shear (mode III) loading conditions. Examples are presented to illustrate some capabilities of the method.     

Assessment of conservative load transfer for fluid–solid interface with non‐matching meshes

We present a detailed comparative study of three conservative schemes used to transfer interface loads in fluid–solid interaction simulations involving non‐matching meshes. The three load transfer schemes investigated are the node‐projection scheme, the quadrature‐projection scheme and the common‐refinement based scheme. The accuracy associated with these schemes is assessed with the aid of 2‐D fluid–solid interaction problems of increasing complexity. This includes a static load transfer and three transient problems, namely, elastic piston, superseismic shock and flexible inhibitor involving large deformations. We show how the load transfer schemes may affect the accuracy of the solutions along the fluid–solid interface and in the fluid and solid domains. We introduce a grid mismatching function which correlates well with the errors of the traditional load transfer schemes. We also compare the computational costs of these load transfer schemes. Copyright © 2005 John Wiley & Sons, Ltd.     

The effect of nanotube radius on the constitutive model for carbon nanotubes

We investigate the effect of nanotube radius on the constitutive model of single wall carbon nanotubes. We adopt a modified Cauchy–Born rule to incorporate the interatomic potential into the continuum analysis, and such an approach ensures the equilibrium of atoms. It is shown that the nanotube radius has little effect on the mechanical behavior of single wall carbon nanotubes subject to simple tension or pure torsion, while the nanotube orientation has somewhat larger influences.     

Frontal polymerization accelerated by continuous conductive elements

Frontal polymerization (FP), a propagating reaction wave driven by exothermic polymerization, is increasingly considered for the rapid fabrication of fiber-reinforced composites. However, the effect of the fibers on the FP reaction has not yet been explored. In this contribution, we demonstrate that thermally conductive continuous elements accelerate FP using an experimental model system and finite-element-based numerical simulations. Furthermore, the degree of acceleration is shown to be affected by the amount of available monomer in the system. These results suggest that thermally conductive carbon fiber reinforcement may facilitate FP for composite manufacturing. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47418.     

Shape optimization using a NURBS‐based interface‐enriched generalized FEM

This study presents a gradient‐based shape optimization over a fixed mesh using a non‐uniform rational B‐splines‐based interface‐enriched generalized finite element method, applicable to multi‐material structures. In the proposed method, non‐uniform rational B‐splines are used to parameterize the design geometry precisely and compactly by a small number of design variables. An analytical shape sensitivity analysis is developed to compute derivatives of the objective and constraint functions with respect to the design variables. Subtle but important new terms involve the sensitivity of shape functions and their spatial derivatives. Verification and illustrative problems are solved to demonstrate the precision and capability of the method. Copyright © 2016 John Wiley & Sons, Ltd.     

Design of actively-cooled microvascular materials: a genetic algorithm inspired network optimization

Structural and Multidisciplinary Optimization - The design of a microvascular flow network embedded in an actively-cooled polymeric material is presented. A multi-objective Genetic Algorithm (GA)...     

Computational modeling and design of actively-cooled microvascular materials

The computational modeling and design of an actively-cooled microvascular fin specimen is presented. The design study is based on three objective functions: (i) minimizing the maximum temperature in the thermally loaded fin, (ii) optimizing the flow efficiency of the embedded microchannel, and (iii) minimizing the void volume fraction of the microvascular material. A recently introduced Interface-enriched Generalized Finite Element Method (IGFEM) is employed to evaluate the temperature field in a 2D model of the specimen, allowing for the accurate and efficient capturing of the gradient discontinuity along the fluid/solid interface without the need of meshes that conform to the geometry of the problem. Finding the optimal shape of the embedded microchannel is thus accomplished with a single non-conforming mesh for all configurations. Prior to the optimization study, the IGFEM solver is validated through comparison with infrared measurements of the thermal response of an epoxy fin with a sinusoidal microchannel.