Date of Award

Spring 2004

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Aerospace Engineering

Committee Director

Osama Kandil

Committee Member

Oktay Baysal

Committee Member

Drew Landman

Call Number for Print

Special Collections; LD4331.E535 G42 2004

Abstract

During airfoil stall condition, the flow over airfoil loses its momentum, creating high pressure zones and adverse pressure gradients on the airfoil upper surface. When the adverse pressure forces and viscous forces get greater than the flow momentum, the flow can no longer remain attached on the surface and separates towards a low pressure zone.

In order to eliminate separation, the low momentum flow on the suction side should be predicted and removed from the airfoil surface to maintain high momentum and low pressure flow conditions over the airfoil. This study is conducted to apply active computational sensing and control with a variety of synthetic jet design parameters for a NACA-0012 airfoil at stall angles of attack using the unsteady Navier-Stokes equations. Single, double and triple synthetic jets are placed at ports, which are located on the airfoil upper surface near the leading edge, middle and trailing edge. The influences of the synthetic jet's locations, direction, intensity, frequency, phase and operation sequence are investigated. To get suitable jet driving frequencies, pressure where adverse pressure gradients form is computationally sensed and fundamental frequencies of pressure fluctuations arc obtained using Fast Fourier Transform. One or more of the frequencies are fed back to drive the synthetic jets. Synthetic jet direction angles are configured such that they are alternated with respect to the jet being suction or blowing. The new developed synthetic jet has been called the synchronized alternating-angle direction oscillatory (SAADO) synthetic jet. Best combinations of the SAADO parameters are obtained by running systematic multiple cases, which are targeted to find their optimum values.

Results show that SAADO synthetic jet controllers eliminate the separation to a large extent. Single port control increases the airfoils performance at a limited range. However, multiple port control gives actual boast. Two ports control gives the lowest drag as well as highest lift-to-drag ratio and three ports control gives the highest lift production.

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DOI

10.25777/1nha-rg67

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