Effects of Metal Foam Porosity, Pore Size, and Ligament Geometry on Fluid Flow

Abstract

This paper explores the effects of porosity, pore size, and ligament geometry in metal foams on its fluid flow capability. The motivation to understand this phenomenon stems from exploring the use of metal foams for thermal energy dissipation applications where both thermal convection and fluid flow are desired. The goal of this research is to identify the optimum configuration of metal foam design parameters for maximum flow. To study the impacts of said parameters, an experimental study of air flow through open cell metal foams is performed. Seven foam blocks were used in this partial factorial study, representing varying materials, pore size, and porosity. Wind tunnel tests are performed to measure the velocity of air flowing through the foam as a function of the free stream air velocity. Multinomial logit regression was performed to analyze the effects of the design parameters on velocity loss through the foam. Results indicate that effect of porosity on velocity loss is significant while that of pore size is insignificant. However, one test result did not fit this trend and further investigation revealed that this was due to varying ligament geometry in outlier metal foam. The cross section shape of the ligaments varied from a convex triangular shape to a triangle shape with concave surfaces, increasing the amount of drag in the airflow through the sample.