The momentum flux of turbulent impinging jet is not conserved causing a transfer of momentum between the jet and its ambient, which may result in either increasing or decreasing the momentum flux of the jet. In order to study the nature of the momentum variation, the reaction force of an axisymmetric jet was measured by issuing the jet from a round nozzle against a plate which is placed on a digital balance.
Tests were carried out in an almost infinite ambient with different heights for Reynolds between 5.5 * 10 power 4 and 6.4 * 10 power 4 . Different sizes of ceilings were installed around the nozzle to examine the influence of the air entrainment from ceiling level into the jet. Visualization was performed to understand better the effect of the entrainment.
The results show, after a certain distance, the reaction force becomes larger than the momentum flux at the inlet. By using wider ceilings around the jet supply outlet, the reaction force, which is normalized by the inlet momentum, was slightly decreased.
Source: University of Gävle
Author: Xue, Fei
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