Separation Control using Synthetic Jet Actuators
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The suppression of post-stall separation over an unconventional 2-D airfoil at moderate Reynolds numbers (up to 106) using transverse synthetic (zero net mass flux) jet actuators is discussed. As shown by the authors in earlier investigations, the apparent modification of the surface shape by the interaction domain between the actuator jets and the cross flow results in a local displacement of the cross flow streamlines. The concomitant modification of the streamwise pressure gradient upstream of where the flow nominally separates in the baseline configuration can lead to complete suppression of separation over a significant range of angles of attack in the post-stall domain. While in the absence of flow control the airfoil is stalled at angles of attack exceeding 5°, actuation leads to either completely or partially attached flow within the entire range of angles tested (up to 25°) that is accompanied by a dramatic increase in lift and a corresponding decrease in pressure drag. Actuation is typically effected at frequencies that are an order of magnitude higher than the characteristic (shedding) frequency of the airfoil [i.e., St ~ O(10) rather than St ~ O(1)]. When the actuation frequency St is O(1), the reattachment is characterized by a Coanda-like tilting of the separated shear layer and the formation of large vortical structures at the driving frequency that persist beyond the trailing edge of the airfoil and lead to unsteady attachment and consequently to a time-periodic variation in vorticity flux and in circulation. In contrast, the suppression of separation at high actuation frequencies [i.e., St = O(10)] is marked by the absence of organized vortical structures along the flow surface. Finally, the dynamics of the transient lift in controlled reattachment and separation are investigated using pulsed amplitude modulation of the actuation input.
KeywordsCross Flow Aerodynamic Performance Separate Shear Layer Pressure Drag Separation Control
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- Ahuja, K. K. and Burrin, R. H. (1984). Control of Flow Separation by Sound. AIAA Paper 84–2298.Google Scholar
- Amitay, M., Honohan, A., Trautman, M. and Glezer, A. (1997). Modification of the Aerodynamic Characteristics of Bluff Bodies using Fluidic Actuators. AIAA Paper 97–2004.Google Scholar
- Amitay, M., Smith, B. L. and Glezer, A. (1998). Aerodynamic Flow Control using Synthetic Jet Technology. AIAA Paper 98–0208.Google Scholar
- Amitay, M. and Glezer, A. (1999). Aerodynamic Flow Control of a Thick Airfoil Using Synthetic Jet Actuators. FEDSM99–6922, Proceedings of the 3rd ASME/JSME Joint Fluids Engineering Conference, San Francisco, California.Google Scholar
- Amitay, M., Kibens, V., Parekh, D. E. and Glezer, A. (1999). Flow Reattachment Dynamics over a Thick Airfoil Controlled by Synthetic Jet Actuators. AIAA Paper 99–1001.Google Scholar
- Donovan, J. F., Kral, L. D. and Cary, A. W. (1998). Active Flow Control Applied to an Airfoil“. AIAA Paper 98–0210.Google Scholar
- Erk, P. (1997). Separation Control on a Post-Stall Airfoil Using Acoustically Generated Perturbations. Ph.D. Dissertation, Technische Universitat Berlin, Germany.Google Scholar
- Huang, L. S., Maestrello, L. and Bryant, T. D. (1987). Separation Control over an Airfoil at High Angles of Attack by Sound Emanating from the Surface. AIAA Paper 87–1261.Google Scholar
- Smith, B. L. and Glezer, A. (1998). The Formation and Evolution of Synthetic Jets. Physics of Fluids, Vol. 10, No. 9.Google Scholar
- Smith, D. R., Amitay, M., Kibens, V., Parekh, D. E. and Glezer, A. (1998). Modification of Lifting Body Aerodynamics using Synthetic Jet Actuators. AIAA Paper 98–0209.Google Scholar
- Williams, D., Acharya, M., Bernhardt, J., and Yang, P. (1991). The Mechanism of Flow Control on a Cylinder with the Unsteady Bleed Technique. AIAA Paper 91–0039.Google Scholar