Begell House
International Journal for Multiscale Computational Engineering
International Journal for Multiscale Computational Engineering
1543-1649
15
3
2017
MOLECULAR DYNAMICS STUDY ON INTERFACIAL THERMAL RESISTANCE BETWEEN ORGANIC NANOPARTICLES AND ALKALI MOLTEN SALT MIXTURES
.Interfacial thermal resistances between organic nanoparticles and liquid alkali molten salt mixtures were estimated using molecular dynamics simulations. In order to understand the interfacial thermal resistance behaviors as to differ-ent particles, three carbon particles—single-wall carbon nanotube (SWNT), fullerene (C60), and graphite sheets—were employed in this study. Transient heat transfer between a carbon particle and molecules of the molten salt mixtures were simulated on the basis of the lumped capacitance method. The effects of material properties, and particle shapes and sizes on the interfacial thermal resistance were investigated. Additionally, the characteristics of the molten salt mixture molecules in liquid phase were comprehended by plotting local density variations along the relative position from the particle: the existence of the compressed liquid layer was confirmed. Finally, the interfacial thermal resistance of functionalized SWNT using two functional groups (carboxylic and amine groups) was estimated and also the critical diameter of the nanoparticle which maximizes the thermal conductivity and the specific heat capacity of molten salt nanofluids was predicted.
Byeongnam
Jo
Department of Mechanical Engineering, Ajou University, Worldcup-ro 206, Yeongtong-gu, Suwon, 16499, Republic of Korea; Department of Mechanical Engineering, Texas A&M University, College Station, Texas 77843, USA
Debjyoti
Banerjee
Texas A&M University, Mechanical Engineering, MS 3123 TAMU, College Station, TX 77843-3123, USA
199-217
MODELING OF THIN COMPOSITE LAMINATES WITH GENERAL ANISOTROPY UNDER HARMONIC VIBRATIONS BY THE ASYMPTOTIC HOMOGENIZATION METHOD
A new approach to the asymptotic homogenization theory for thin composite laminates with general anisotropy of elastic modules under harmonic vibrations is suggested. The main purpose of the theory is to derive a closed explicit equation system for all six stress tensor components in composite laminates under vibrations, using 3D general equations for steady oscillations of elastic solids, by the asymptotic homogenization method. Unlike the classical homogenization analysis of 3D periodicity structures, our approach was applied to thin laminates with a constant thickness, but without any periodicity through the plate thickness. Recurrent chains of local vibration problems were deduced by the homogenization method, and closed-form solutions of these problems were found for thin laminates. This method allows us to compute all six stresses’ distributions in a plate including normal through-thickness and shear interlayer stresses for the case of general anisotropy in elastic modules. Unlike the classical plate theories, for the case of general anisotropy in elastic modules, when there are 21 elastic constants, the displacements’ distribution through a plate thickness is not linear. Longitudinal displacements proved to be linear functions of the coordinate along a plate thickness only for special anisotropy types — for monoclinic materials of plate layers, whose elastic modules’ symmetry plane is parallel to a middle plane of the plate. Computations by the developed method and by a 3D-?nite-element method solving the three-dimensional problem on free vibrations were compared, which showed a high accuracy of the developed method in calculation of natural frequencies and all six stresses in the plate.
Yu. I.
Dimitrienko
Computational Mathematics and Mathematical Physics Department, Bauman Moscow State Technical University, 2-nd Baumanskaya Str., 5, Moscow, 105005, Russia
I.D.
Dimitrienko
Computational Mathematics and Mathematical Physics Department, Bauman Moscow State Technical University, 2-nd Baumanskaya Str., 5, Moscow, 105005, Russia
219-237
A COUPLED COMPUTATIONAL APPROACH FOR THE SIMULATION OF SOIL EXCAVATION AND TRANSPORT IN EARTH-PRESSURE BALANCE SHIELD MACHINES
A prototype modeling framework for the coupled simulation of excavation processes at the tunnel face and the subsequent
transport of the foam-soil mixture within the pressure chamber of EPB shield machines is proposed. The discrete
element method is used for the modeling of soil excavation and the stabilized finite element method, using a non-
Newtonian fluid model, is employed for the modeling of fluid transport. A variational approach is applied to directly
obtain interparticle parameters of the DEM from a macroscopic strength criterion. A 2D numerical simulation model for a simplified representation of the cutting process at the tunnel face and the transport of the excavated soil-foam mixture is used to demonstrate the proposed coupled excavation-transport modeling approach. According to the proposed coupled DEM-FEM model, the mass flow obtained from the excavation simulation by means of the DEM serves as the
input for the finite element flow simulation to generate the pressure distribution within the excavation chamber. It is
shown that the proposed approach helps to obtain insight into the coupled excavation and transport processes at the
tunnel face and the spatiotemporal distribution of the face pressure.
Thai Son
Dang
Institute for Structural Mechanics, Ruhr-Universität Bochum
Nicola
Wessels
Institute of Mechanics of Materials, Ruhr-Universität Bochum
Ngoc-Son
Nguyen
GeM Institute, University of Nantes
Klaus
Hackl
Institute of Mechanics of Materials, Ruhr-Universität Bochum
Günther
Meschke
Institute for Structural Mechanics, Ruhr-Universität Bochum
239-264
A STOCHASTIC INVERSE PROBLEM FOR MULTISCALE MODELS
Descriptions of complex multiscaled physical systems often involve many physical processes interacting through a
multitude of scales. In many cases, the primary interest lies in predicting behavior of the system at the macroscale (i.e., engineering scale) where continuum, physics-based, models such as partial differential equations provide high-fidelity descriptions. However, in multiscale systems, the behavior of continuum models can depend strongly on microscale properties and effects, which are often included in the macroscale model as a parameter field obtained by some upscaling process from a microscale model. Generally, a number of choices have to be made in choosing an upscaling
procedure and the resulting representation of the parameter. These choices have a strong impact on both the fidelity and
the computational efficiency of the model. Thus, choosing a good parameter representation and upscaling procedure
becomes part of the uncertainty quantification and prediction problem for a multiscale model. We consider the use of output data from the macroscale model to formulate and solve a stochastic inverse problem to determine probability information about the upscaled parameter field. In particular, we extend a measure-theoretic inverse problem frame-work and non-intrusive sample-based algorithm to determine the choices of parameter representation and upscaling procedure that are most probable given uncertain data from the macroscale model.We illustrate the methodology in the context of shallow water flow and sub-surface flow.
N.
Panda
Department of Statistics, Colorado State University, Fort Collins, Colorado 80523-1877, USA
Troy
Butler
Department of Mathematical and Statistical Sciences, University of Colorado Denver, Colorado
80217, USA
Donald
Estep
Department of Statistics, Colorado State University, Fort Collins, Colorado 80523-1877, USA
Lindley
Graham
Department of Scientific Computing, Florida State University, Tallahassee, Florida 32306,
USA
Clint
Dawson
The Institute for Computational Engineering and Sciences, University of Texas at Austin,
Austin, Texas 78712, USA
265-283