An experimental study of the effects of nozzle forcing on the turbulent three-dimensional wall jet

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University of New Brunswick


It has been demonstrated in the literature that the development of free jets can be controlled by manipulating the nozzle discharge conditions through actuation. However, there has been very little attention to controlling the three-dimensional wall jet. Unlike free jets, the development of the turbulent three-dimensional wall jet is quite different in that the lateral growth is 5 to 8 times large than the vertical growth. This is attributed to the coherent structures present in the wall jet. In the present investigation, a three-dimensional turbulent wall jet with a Reynolds number of 133000 was subjected to forcing applied at the nozzle exit to evaluate the feasibility of control. Forcing was provided by an array of 8 zero net mass flux synthetic jets, which were mounted circumferentially around the edge of the nozzle exit. The effectiveness of the control was monitored by an array of microphones that consisted of 89 condenser microphones to measure unsteady fluctuating wall pressure and PIV measurements to the evaluate velocity of the wall jet. These measurements were taken from a x/D = 5 to 15 in the streamwise direction and z/D = -4 to 4 in the lateral direction. Several experiments were conducted to examine how forcing frequency, phase and spatial configuration affect the development of the three-dimensional turbulent wall jet. Control was demonstrated to be feasible with upwards of 140% increase in lateral half-width and a lateral shift in Umax of upwards of x/D = 0.6.