Author(s)

C. Lin, Y.-C. Su, P.-H. Yeh & R. V. Raikar

Abstract

The velocity-field characteristics of time-dependent horseshoe vortex flow at the juncture of an upright square cylinder and a base plate, which is subjected to an unsteady dam-break flow, were investigated experimentally. Flow visualization techniques and high-speed particle image velocimetry (HSPIV) were used to explore both qualitatively and quantitatively the unsteady feature of the flow field of horseshoe vortex structure at the juncture of square cylinder and base plate, respectively. The characteristics of the evolutionary horseshoe vortex system were analyzed, including the position of primary vortex core, down-flow velocity profile and the circulation of primary horseshoe vortex. The results show that air bubble entrains into the vortex centre in front of the model only in the cases with model-width varying from 3.0 cm to 5.0 cm. When the model width increases, the bubble entraining to the vortex centre occurs earlier. The results also show that the down-flow velocity profiles are highly affected by the vortex structures. The relationship between flow characteristics and the time duration after the gate is open is obtained by using regression analysis. The similarity of the position of the down-flow is presented with dimensionless length and dimensionless velocity as length and velocity scales, respectively. Keywords: dam-break flow, horseshoe vortex, flow visualization technique, highspeed particle image velocimetry, air entrainment.

Keywords

dam-break flow, horseshoe vortex, flow visualization technique, highspeedparticle image velocimetry, air entrainment.