FLOW CHARACTERISTICS AND VELOCITY FIELDS OF SWIRLING DOUBLE-CONCENTRIC JETS AT HIGH CENTRAL JET REYNOLDS NUMBERS

Minh Duc Le ； Ching Min Hsu ； Rong Fung Huang

《Journal of Marine Science and Technology》 26卷5期 (2018/10) Pp. 629-637

https://doi.org/10.6119/JMST.201810_26(5).0002

摘要

The flow characteristics and velocity fields of swirling double-concentric jets at a high central jet Reynolds number were studied. The central jet Reynolds numbers varied from 700 ＜ Re_c ＜ 1000. The flow behaviors of the swirling double-concentric jets were observed using a laser light sheet assisted by a smoke-wire flow visualization technique. The time-averaged velocity vectors and streamlines, normalized velocity contours, fluctuation intensity contours, and vorticity contours were carried out using particle image velocimeter (PIV). Two characteristic flow modes are classified: the central jet-dominated radial flow occurs at a low annular jet Reynolds number while the high-turbulence swirling wake appears at a high annular jet Reynolds number. The flow feature of the central jet-dominated radial flow presents a wide-open shear layer because of the effect of a high-speed deflected central jet. A large dual-ring vortex in the wake and two pairs of vortices in the gap between the control disk and primary disk in the high-turbulence swirling wake mode appear. The turbulence intensity in the high-turbulence swirling wake were significantly larger than those in the central jet-dominated radial flow.

關鍵字

double-concentric jets ； bluff-body wake ； flow visualization ； PIV