Effect Of Tab Geometry On The Development Of A Jet Issuing From A Rectangular Nozzle

An experimental investigation was carried out to study the effect of tab geometry on the flow characteristics of a jet issuing from a 2: 1 rectangular nozzle using two-component hotwire anemometry. A pair of tabs of trapezoidal and square configurations (2% total blockage area) is placed on the minor-axis side of the rectangular nozzle and tested for two tab inclination angles of 135 degrees and 45 degrees, respectively. Tests were conducted for a nominal jet exit velocity of 20 ms(-1) corresponding to a Reynolds number based on nozzle equivalent diameter of 5.02 x 10(4). Relative to the plain jet, the potential-core length of the jet with trapezoidal tabs shows a reduction of 62% while the jet with square tabs shows a reduction of 75%, respectively. This is also accompanied by a significant upstream shift in peak centerline turbulence intensity (u'/=U-e). The tab inclination of 135 degrees results in further enhanced jet characteristics in each case. The presence of each tab configuration is observed to inhibit the jet growth along the minor-axis plane thereby introducing large distortion in the jet cross-sectional development that ultimately leads to jet-core bifurcation along its major-axis. However, it is observed that while the jet with trapezoidal tabs switches its axis at some downstream location, the jet with square tabs does not switch axis at all. This indicates a strong influence of tab geometry on the overall jet flow development.