Geometric and Fluid-Dynamic Characterization of Actual Open Cell Foam Samples by a Novel Imaging Analysis Based Algorithm

摘要

Metallic open-cell foams have proven to be valuable for many engineering applications. Their success is mainly related to mechanical strength, low density, high specific surface, good thermal exchange, low flow resistance and sound absorption properties. The present work aims to investigate three principal aspects of real foams: the geometrical characterization, the flow regime characterization, the effects of the pore size and the porosity on the pressure drop. The first aspect is very important, since the geometrical properties depend on other parameters, such as porosity, cell/pore size and specific surface. A statistical evaluation of the cell size of a foam sample is necessary to define both its geometrical characteristics and the flow pattern at a given input velocity. To this purpose, a procedure which statistically computes the number of cells and pores with a given size has been implemented in order to obtain the diameter distribution. In particular, a morphological characterization of an actual foam sample was performed by applying an image processing method. The analyzed foam was a cubic open-cell foam made by Silicon Carbide (SiC). Secondly, the pressure drop characterization of the foam sample was performed by means of CFD simulations. In particular, the relative importance of the viscous term and the inertial term was assessed. This analysis was performed including the effect of the porosity and of the mean pore diameter. The pressure gradient was parametrized with respect to such properties, passing through the concept of porosity and morphology. Additionally, the role of turbulence modeling in the simulation of the flow through the foam sample was investigated, finding that the flow pattern is not necessarily laminar and the turbulence is related to the fluid inertia.