| Summary: | An experimental investigation regarding the dynamic stall of various swept wing models with pitching motion was performed to analyze the effect of sweep on the dynamic stall. The experiments were performed on a wing with a NACA0012 airfoil section with an aspect ratio of AR = 4. The experimental study was conducted for chord-based Reynolds number Re<sub>c</sub><inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo> </mo><mo>=</mo><mn>2</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mn>5</mn></msup></mrow></semantics></math></inline-formula> and freestream Mach number <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>M</mi><mi>a</mi><mo>=</mo><mn>0.1</mn></mrow></semantics></math></inline-formula>. First, a ‘particle image velocimetry’ (PIV) experiment was performed on the wing with three sweep angles, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi mathvariant="sans-serif">Λ</mi><mo>=</mo><msup><mn>0</mn><mi mathvariant="normal">o</mi></msup><mo>,</mo><mo> </mo><msup><mrow><mn>15</mn></mrow><mi mathvariant="normal">o</mi></msup><mo>,</mo><mo> </mo><mi>and</mi><mo> </mo><msup><mrow><mn>30</mn></mrow><mi mathvariant="normal">o</mi></msup></mrow></semantics></math></inline-formula>, to obtain the flow structure at several wing spans. The results obtained at a reduced frequency showed that a laminar separation bubble forms at the leading edge of the wing during upward motion. As the upward pitching motion continues, a separation burst occurs and shifts towards the wing trailing edge. As the wing starts to pitch downward, the growing dynamic stall vortex (DSV) vortex sheds from the wing’s trailing edge. With the increasing sweep angle of the wing, the stall angle is delayed during the dynamic motion of the wing, and the presence of DSV shifts toward the wingtip. During the second stage, a ‘turbo pressure-sensitive paint’ (PSP) technique was deployed to obtain the phase average of the surface pressure patterns of the DSV at a reduced frequency, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>k</mi><mo>=</mo><mn>0.1</mn></mrow></semantics></math></inline-formula>. The phase average of pressure shows a distinct pressure map for two sweep angles, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi mathvariant="sans-serif">Λ</mi><mo>=</mo><msup><mn>0</mn><mi mathvariant="normal">o</mi></msup><mo>,</mo><mo> </mo><msup><mrow><mn>30</mn></mrow><mi mathvariant="normal">o</mi></msup></mrow></semantics></math></inline-formula>, and demonstrates a similar trend to that presented in the published computational studies and the experimental data obtained from the current PIV campaign.
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