Author(s): Q. S. Qiao; Joseph H. W. Lee; Lam K. M.
Linked Author(s): Joseph Hun-Wei Lee
Keywords: Vortex flow; Swirling flow; Air Core; Drainage system; Drop shaft
Abstract: This paper presents experimental results of a steady tangential vortex intake flow. The velocity field is measured with Laser Doppler Anemometry for the first time. It is found that the vortex intake flow pattern is basically divided into two regimes according to the variable drop shaft inflow velocity field. For a flow less than the free drainage discharge, the inflow does not interfere with the swirling flow in the drop shaft; the horizontal and vertical velocity of the inflow in the tapering channel varies linearly and parabolically with the vertical distance respectively. For larger discharges the inflow velocity field is notably modified by the drop shaft swirling flow. It is observed that the swirling flow possesses a stable and asymmetrical 'D' shaped air core with a throat located at the lowest level of the tapering channel. The tangential velocity of the swirling flow near the throat can be well-approximated by a Rankine vortex model in the region where the flow layer thickness is of the same order as the junction width; the vertical velocity of the swirling flow is approximately constant in the radial direction.