Control of leading edge vortex and three-dimensional surface separation on a non-slender delta wing using passive and active techniques

Date

2024-11-19

Author

Çetin, Cenk

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In line with the progress achieved in unmanned aerial vehicle (UAV) technologies in recent decades, interest in the control of flow structures over delta wing planforms, which constitute the baseline for such vehicles, has significantly increased. As product phases advance from conceptual design to operational prototypes, performance, efficiency, and stability targets have become the focus for the industry. To benefit from the advantages of delta wing planforms, the control of flow structures has been a major concern for researchers and industry, allowing for the expansion of the operational envelopes of such platforms, particularly where high angles of attack and lift forces are required. In the present study, the effects of passive bleeding and active periodic blowing flow control techniques on flow physics over a Λ = 45o swept delta wing with a thickness-to-chord ratio of t/C=5.9 were experimentally investigated. For the passive bleeding technique, an innovative nozzle-type bleeding geometry design aimed at increasing the bleeding momentum was studied using surface pressure, force, and particle image velocimetry measurements. The results suggest that the nozzle-type bleeding design is quite effective in altering the flow structure and aerodynamic coefficients. Additionally, a bleeding momentum estimation method was developed based on surface pressure measurements by utilizing the Bernoulli equation and a loss coefficient calibrated with in-situ hot wire measurements. For the periodic blowing technique, a comprehensive active flow control system based on fast-switching actuators was built and characterized prior to aerodynamic measurements, using in-situ hot-wire measurements. Characterization results indicated that a full investigation of such systems provides valuable calibration schemes, which are crucial for assessing the aerodynamic benefits and developing possible closed-loop flow control systems. The effect of periodic blowing actuation in the form of regular and burst-modulated square waves, applied through the leading edges, was examined using surface pressure and force measurements. Results showed that periodic actuation is quite effective in improving and recovering the suction pressure coefficient, particularly at high angles of attack, which was associated with an improvement in stall behavior, as evidenced by force measurements.

Subject Keywords

Experimental aerodynamics, Non-slender delta wing, Three dimensional surface separation, Passive flow control, Bleeding momentum, Active flow control, Periodic blowing, In-Situ calibration

URI

https://hdl.handle.net/11511/112670

Collections

Graduate School of Natural and Applied Sciences, Thesis