Corrosion sample streamlining to enhance the performance of the rotating cage testing setup

Abstract

Computations of the flow inside the rotating cage, a widely used testing methodology for flow-accelerated corrosion studies, are presented in this study. The main objectives here are to elucidate the flow behaviour inside the cage geometry that is recommended by the American Society for Testing and Materials (ASTM) and to investigate the effects of streamlining the shape of the cuboid sample recommended by ASTM. The streamlined sample profile considered here comprises a semi-circular leading edge, a triangular trailing edge and a flat mid-section with uniform thickness. It is found that the low value of the ratio of radius of rotation to sample length in the standard geometry makes it difficult to completely eliminate flow separation. Nonetheless, the flow is attached to the streamlined samples at locations of interest to corrosion measurements which inflicts more shear on the samples’ surfaces compared to the flow around the conventional blunt cuboid samples normally used. Moreover, we discuss the unsteadiness of the samples’ wakes and how the flow recirculation behaves differently, depending on both the sample shape and the flow Reynolds number.