Modeling of capillary rise in an annular geometry

Abstract

The presence of water in the small gaps of aluminum rivets and screw fasteners appears to cause million-dollar problems. This problem has been observed, for example, on the fuselage of some aircraft, with significant implications for the lifetime of the plane. Capillary forces draw water into gaps between the rivet or screw and the facing surface causing corrosion problems. Aluminum surface is to be modified to retard or prevent the corrosion by means of minumization of the water uptake. In order to do so, knowing how much water drawn into such gaps is necessary. Modeling of capillary rise in an annular geometry was investigated in this study. Models were developed based on the curvature of the surface and the height of the rising liquid. Experiments on capillary rise in an annulus for water-air was carried out at ambient conditions to validate the model. It was found that the model of the surface shape agreed well with the the experimental results. The heights of rising water from the flat water surface to the bottom of the meniscus were 16.14 and 14.32 mm at the right-hand side and left-hand side, respectively, where the height calculated from the model was 18.2 mm. This difference was due to the large annular gap width, whidth, which is less accurate than a small gap width.