Stereoscopic Particle Image Velocimetry data from a 2-bladed rigid NACA0013 rotor undergoing retreating blade dynamic stall in a low-speed wind tunnel, are analyzed to understand the phenomenon of 3-dimensional reattachment at the end of the dynamic stall cycle. Continuing from prior studies on the inception and progression of 3-D rotating dynamic stall for this test case, phase-resolved, ensemble-averaged results are presented for two values of rotor advance ratio at two spanwise stations along the blade. The results show the nominal reattachment getting delayed in rotor azimuth with higher advance ratio. At low advance ratio reattachment starts at the leading-edge and progresses towards the trailing-edge with a vortex shedding transporting excess vorticity sheds from the leading-edge and convects away, with the flow reattaching behind it. At higher advance ratio, the vortical structure shrinks in size while the flow close to the trailing-edge appears to reattach. Spanwise vorticity transport appears to be the mechanism. The difference could be attributed to the lower chordwise velocity of the blade at higher advance ratio, bringing in a rotation effect.
- Fluids Engineering Division
A Study of 3-Dimensional Reattachment on Rotor Blades After Dynamic Stall
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Raghav, V, Hiremath, N, & Komerath, N. "A Study of 3-Dimensional Reattachment on Rotor Blades After Dynamic Stall." Proceedings of the ASME 2016 Fluids Engineering Division Summer Meeting collocated with the ASME 2016 Heat Transfer Summer Conference and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels. Volume 1B, Symposia: Fluid Mechanics (Fundamental Issues and Perspectives; Industrial and Environmental Applications); Multiphase Flow and Systems (Multiscale Methods; Noninvasive Measurements; Numerical Methods; Heat Transfer; Performance); Transport Phenomena (Clean Energy; Mixing; Manufacturing and Materials Processing); Turbulent Flows — Issues and Perspectives; Algorithms and Applications for High Performance CFD Computation; Fluid Power; Fluid Dynamics of Wind Energy; Marine Hydrodynamics. Washington, DC, USA. July 10–14, 2016. V01BT14A010. ASME. https://doi.org/10.1115/FEDSM2016-7692
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