Local convective mass transfer on circular cylinder with transverse annular fins in crossflow

An experimental study was made of local mass transfer from a circular cylinder, which is situated between two annular fins in a crossflow. Low turbulence-intensity wind tunnel experiments were conducted over moderate Reynolds numbers, 33 000 < Re_d, < 80 000. Velocity measurements were analyzed to examine the characteristics of the boundary layer, which is developed on the flat annular fin. The naphthalene sublimation technique was employed to measure the local convective mass transfer around the circular cylinder. The ratio of the axial gap distance between two axial fins (L) to the radial protrusion length of the annular fin (H) was an important experimental parameter, and its range was 0 < L/H < 0.40. The impact of horseshoe vortices on local mass transfer was scrutinized. For a small gap distance (L/H = 0.05), naphthalene sublimation is intense in the front portion of the cylinder, especially near the separation region. When the gap distance is moderate (L/H = 0.15), the overall character of sublimation shows a more organized pattern. The influence of horseshoe vortices is substantial. For a large gap distance (L/H = 0.40), a dominant role of horseshoe vortices near the corner junction is discernible.