Performance enhancement of a vertical tail using synthetic jet actuators: Flow physics

The performance enhancement of a vertical tail using synthetic jet actuators may allow for a decrease in tail size, which would result in a reduction of the drag, weight, and fuel consumption of the airplane. The potential for enhancement was investigated during wind tunnel experiments on a l/19^th scale model of a Boeing 767 vertical tail at a Reynolds number of 350, 000. The model was instrumented with twelve finite span synthetic jet actuators placed slightly upstream of the rudder hinge-line with the objective of controlling the separation that commenced over the rudder when it was deflected to high angles. Stereo Particle Image Velocimetry (SPIV) was used to explore the interaction of the synthetic jets with the flow near the mid-span of the rudder (and at a moderate rudder deflection). Time-averaged measurements showed that along and outboard of the jets' trajectory separation was reduced, and inboard there were recirculation regions that were visible in spanwise planes. These regions were associated with reduced total velocity. Furthermore, phase-averaged data revealed concentrations of vorticity that were related to the jets. Among these concentrations, the negative streamwise vorticity maintained their coherence farthest downstream. These features appeared to have a notable impact on the flow field. Moreover, the strength of these concentrations dissipated more quickly in the downstream direction as the number and spanwise density of jets increased. This indicated that at the conditions that were tested the jets actually had a detrimental effect on one another.