Salvatore Cunsolo

Effects of ligaments shape on radiative heat transfer in metal foams

Purpose – The purpose of this paper is to investigate the impact of ligament shape on radiative behavior, with a specific focus on the inter-dependence among porosity, ligament shape and radiative characteristics. Design/methodology/approach – Using Surface Evolver to generate a base structure and then coherently modifying it, the model presented in this paper aims to tackle these challenges in an improved fashion, all the while making it possible to systematically assess the influence of ligament shape on radiation heat transfer in foams, focussing on the porosity-dependence of ligament shape. Findings – It is found that the prediction of numerical models, at constant size and specific surface of the cells, is strongly affected by the dependence of ligament shape on the porosity. Research limitations/implications – The above said dependence has, therefore, to be accounted for in robust modeling of radiation in foams with a wider range of porosities. Originality/value – The radiative behavior of metal foa...

Effective conductivity of Voronoi’s closed- and open-cell foams: analytical laws and numerical results

AbstractThe conductive heat transfer in high-porosity cellular materials is generally treated by defining a homogeneous effective thermal conductivity. Numerous empirical and semiempirical models as well as numerical investigations have already been conducted to estimate this conductivity. These previous investigations were based on simplifications of the morphology of the cellular structure and/or of the method of solution of the heat transfer problem. Moreover, they were developed specifically for a type of foam, thus limiting their range of applicability. In order to improve the theoretical knowledge on this field, we have developed an innovative approach combining Voronoi methods for the generation of representative cellular materials and the finite element method (FEM) for solving the conductive heat transfer. The structures generated are able to reproduce the discriminating details of the microstructure and cover the whole range of open-cell or closed-cell foams commonly used in scientific or industrial applications. The influence of the structural parameters on the effective conductivity is analyzed. Based on this assessment, new simplified analytical relations are deduced accounting for the composition and structural parameters of the material. The validity of these laws has been verified by comparisons with “tomographic” results obtained from 3D tomographic data of real open-cell and closed-cell foams. The analytical correlations are potentially very useful for numerous applications.

Effective Elastic Behavior of Irregular Closed-Cell Foams

This paper focuses on the computational modeling of the effective elastic properties of irregular closed-cell foams. The recent Hill’s lemma periodic computational homogenization approach is used to predict the effective elastic properties. Three-dimensional (3D) rendering is reconstructed with the tomography slices of the real irregular closed-cell foam. Its morphological description is analysed to generate realistic numerical closed-cell structures by the Voronoi-based approach. The influences of the Representative Volume Element (RVE) parameters (i.e., the number of realizations and the volume of RVE) and the relative density on the effective elastic properties are studied. Special emphasis is placed on the appropriate choice of boundary conditions. Satisfying agreements between the homogenized results and the experimental results are observed.