50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

Jan 19, 2012    

4 students from the Flow Control Research Lab attended the AIAA Conference in Nashville, TN earlier this month.

The students and their related abstracts are as follows:

Performance Enhancement of a Vertical Stabilizer using Synthetic Jet Actuators: No Sideslip

Nicholas W. Rathay, Matthew J. Boucher, and Michael Amitay
Rensselaer Polytechnic Institute, Troy, NY 12180, USA
Edward Whalen
The Boeing Company, Hazelwood, MO 36042, USA

Active flow control with synthetic jets has been shown to increase aerodynamic efficiency
by delaying flow separation. Application of flow control to a vertical stabilizer of an aircraft
could enable a significant size reduction of that stabilizer. Wind tunnel experiments were
conducted at Rensselaer Polytechnic Institute on a swept back, tapered stabilizer with a 33%
chord rudder. Flow control was implemented using eight synthetic jet actuators located just
upstream of the hinge-line. The mechanism of enhancement was characterized with surface
pressure measurements and stereoscopic particle image velocimetry (SPIV). Using flow
control, the side force was increased by up to 20% at moderate rudder deflections with
actuators operating at dimensionless frequency O(10). Actuating the synthetic jets with a
pulse-modulated waveform yielded superior performance at high rudder deflections. The
effect of spanwise spacing was also investigated, as was the relative effect of actuators at
different spanwise locations. It was demonstrated that mid-span actuators provide the
greatest contribution at moderate rudder deflections, and root (inboard) actuators provide
the greatest contribution a high deflections. Given that separation propagates from tip to
root as rudder deflection increases, this correlates well with SPIV measurements, which
show that the effect of each actuator is predominantly on a region outboard of its own
position.

 

Dynamic Load Control on a Finite Span Wind Turbine Blade Using Synthetic Jets

Keith Taylor, Chia M. Leong, and Michael Amitay
Rensselaer Polytechnic Institute, Troy, NY 12180, USA

The feasibility of active flow control to mitigate hysteresis loop due to a dynamically pitching finite span s809 blade was investigated experimentally at a Reynolds number of 220,000. Under normal operating conditions, hysteresis loop and tip vibrations exist, which with extended exposure would cause blade fatigue and eventually translate to a reduced lifetime of wind turbines. In this regard, active flow control via arrays of synthetic jet actuators was explored as a means to control flow separation over the finite span blade, which can lead to mitigation of these undesired unsteady loads. In the present work, a six-component load cell was used to measure the aerodynamic loading of lift, drag and pitching moment. Stereoscopic Particle Image Velocimetry (SPIV) measurements were also performed to understand the effects of synthetic jets on flow separation during dynamic pitch, and to correlate these effects to the forces and moment measurements. It was shown that active flow control could delay or minimize dynamic stall through the reduction of the hysteresis loop of the aerodynamic loads. This implies less unsteady aerodynamic loadings on the blade, which can potentially lead to prolonged life of wind turbines.

 

Vortex Formation of a Finite Span Synthetic Jet

Tyler Van Buren and Michel Amitay
Rensselaer Polytechnic Institute, Troy, NY, 12180
Edward Whalen
The Boeing Company, Hazelwood, MO, 63042

The effects of different geometries and input parameters on the flow structures of a finite span synthetic jet are explored in quiescent flow experiments using stereoscopic PIV. Common geometrical parameters, such as neck height, and orifice aspect ratio are varied along with the jet performance characteristics such as Strouhal numbers and Reynolds numbers. Orifice neck heights of 2, 4 and 6mm were tested at aspect ratios of 6, 12, and 18. Jet Strouhal numbers of 0.115 to 0.157 were tested at Reynolds numbers of 615. It is found that as the aspect ratio was increased the size of the vortical structures decreases, the vorticity dissipation rate increases, and axis switching occurred farther away from the orifice. The neck length had a large effect on the structures’ size and strength, their dissipation rate, and the jet’s spreading. Moreover, the driving frequency was found to affect the vortical structures spreading due to the streamwise spacing between structures, as well as drastically affecting dissipation of the structures in both planes.

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