The mechanisms associated with the interaction of an axisymmetric free jet (de = 4 mm; ReUe = 26 500 and 6600) with two continuous control jets on mixing, spreading and direction were examined experimentally. The flow field was visualized and measured using particle image velocimetry, where the interaction of the main jet with the control jets was investigated for different momentum coefficients, streamwise interaction locations and Reynolds numbers. Applying control at low momentum coefficients results in a stabilizing effect, where near the orifice the main jet is stretched such that the turbulent quantities are decreased. However, when control is applied at high momentum coefficients, enhanced mixing and destabilization is obtained, as well as an earlier transition to turbulence and an alteration of the large coherent structures of the main jet. Moreover, the effectiveness of the control jets in altering the main jet flow is more pronounced when the interaction occurs closer to the main jet exit as well as at lower Reynolds numbers.
Journal of Turbulence, Volume 7, Issue 59, 2006.