RISING CURRENT PRODUCTION BY A V-SHAPED PLATE

Abstract

A strong rising current can be produced by placing a V-shaped plate against a horizontal uniform flow. Vortices are formed from the plate, coalesce with the neighboring region ones in the separation zone, then shed downstream. These vortices have a horse-shoe shape and rise due to a self induced upward motion. As the dihedral angle of plates increases, the vortex shedding Strouhal number decreases due to the frequent coalescence in the separation zone. The vortices are intensified by this coalescence, resulting in the formation of higher self-induced velocity. With too large dihedral angles, however, vortices do not rise so high because of the small self-induced velocity. On the other hand, with too small angles, the vortex forms further downstream in the separation zone, which prevents coalescence with others and increases of the vortex intensity, also resulting in the small rising height. Eventually, the rising height shows optimum with the dihedral angle of around 90°. There, the height can reach more than 10 times the plate height. The Strouhal number was found to decrease with increasing Reynolds number, regardless of the dihedral angle.