Date of Award
Summer 2005
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Mechanical & Aerospace Engineering
Program/Concentration
Aerospace Engineering
Committee Director
Osama A. Kandil
Committee Member
Oktay Baysal
Committee Member
Chuh Mei
Call Number for Print
Special Collections; LD4331.E535 K36 2005
Abstract
Flow separation over lifting aerodynamic components, such as airfoils and wings, occurs during stall conditions which are caused by adverse changes (i.e. high angle of attack, inflow conditions, etc.) in the operating conditions of aerodynamic components. During stall conditions, the flow over airfoil loses its momentum, creating high pressure zones on the upper surface of the airfoil and even a small increase in pressure causes the fluid particles to stop and separate to a low pressure zone. In order to eliminate the flow separation, the low momentum flow should be removed in order to maintain the high momentum and low pressure zones over the airfoil.
The present study is conducted to investigate the performance limitations of synchronized, alternating-angle direction, oscillatory (SAADO) synthetic jets for high angles of attack. It also introduces the concept of closed-loop active flow control using SAADO synthetic jets for a NACA 0012 airfoil at post-stall conditions. The synthetic jet is designed such that the jet direction angle changes its sign during suction and blowing phases of the oscillation cycle of diaphragm. The diaphragm oscillation is driven using the fundamental frequency of the separated flow which is found by computationally sensing the separated flow at points downstream of the separation location and using a Fast Fourier Transform (FFT) analysis to obtain it. Single, double and triple synthetic jets are located at control ports which are placed at leading edge, middle and trailing edge of the airfoil upper surface, respectively. The effect of the locations and the operation sequence of synthetic jets, direction angle for suction and blowing phases, driving frequency, phase angle and maximum amplitude for the controllers are investigated. After obtaining the optimum combination of flow control parameters, the concept of closed-loop flow control is introduced. It is based on computational sensing of separated flow at discrete times and at the control ports, using FFT analysis to obtain the corresponding fundamental frequency and applying the new frequency to the corresponding SAADO synthetic jet. Five schemes were introduced to apply the closed-loop flow control. It is investigated for the purpose of adaptation of the flow control to varying flow conditions.
Computational results showed that the performance of SAADO synthetic jets is even better and they are also applicable for high angle of attack. Closed-loop flow control applications increased the average lift coefficient to remarkable values and results indicated that it appears to be promising.
Rights
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DOI
10.25777/fsvf-d137
Recommended Citation
Kamaci, Volkan.
"Computational Sensing and Closed-Loop Active Flow Control of Airfoil at Post-Stall Conditions"
(2005). Master of Science (MS), Thesis, Mechanical & Aerospace Engineering, Old Dominion University, DOI: 10.25777/fsvf-d137
https://digitalcommons.odu.edu/mae_etds/550