Hydrodynamic characteristics of flow in a stochastic foam*

Random nature of stochastic foam provides favorable geometrical properties for thermal applications owing to large specific surface area and high porosity. However, notwithstanding intensive investigations for the last two decades, hydrodynamic characteristics of stochastic foam are still poorly understood. Current 3-D printing technology supports fabrication of transparent complex structures. This study investigates flow characteristics of a stochastic foam. Using micro-tomography and stereo-lithography, a transparent stochastic foam was printed. Quantitative flow visualization was performed using refractive index matching technique and particle image velocimetry. Mixing and drag characteristics were discussed. Mechanical mixing and fast free stream velocity of stochastic foam are beneficial for thermal applications, but large wake area behind the struts causes high pressure drop. On the basis of the results, a novel foam structure is suggested with lower form drag than the stochastic foam but with similar friction drag.