Vortical structures from a two-dimensional nozzle with a bluff-body slot

Abstract

Vortical structures in a two-dimensional (2-D) nozzle with a bluff-body slot under isothermal flow conditions have been examined experimentally and numerically. For these experiments, a 2-D sheet lighting technique coupled with a chemically reacting system was used to observe the vortical shedding processes. By varying the slot flow (flow from the central bluff-body slot), four different types of vortical structures are observed−separated by regions of stability (transition regions). From the sets of data, a flow map was constructed showing the zones occupied by the four different types of vortical structures and the regions of stability. The Reynolds number of the slot flow varied from 7.2 to 291.8; the Reynolds number of the air flow (flow surrounding the bluff-body slot) varied from 50 to 392. For the numerical calculations, the same range of Reynolds numbers for the slot flow was chosen; the Reynolds number of the air flow was fixed at 392. The numerical scheme used is a modified MAC method. Simulated vortical structures were visualized by calculating the flow streaklines. These streaklines agreed with experimental observations. Flow streamlines also have been constructed numerically to characterize the flow fields, particularly the recirculating flow zones, for each type of vortical structures.