On Shedding Frequency and Aerodynamic Characteristics of a Rotating Wire-Wrapped Cylinder 2020-01-0028
Numerical and experimental investigations of shedding frequency of rotating smooth and wire-wrapped cylinders, placed in steady flow have been performed. The freestream mean velocity was 10 m/sec. and for the numerical investigations, the smooth cylinder diameter was 5 cm, which corresponds to an approximate Reynolds number based on cylinder’s diameter of 3.2x104. The wire-wrapped cylinder had a wire diameter of 5 mm and the ratios of pitch spacing to the cylinder diameter, p/D, was 1.0. The cylinder length to diameter ratio was 20. The rotation rates (λ) were 0.5 and 2.0. To obtain the shedding frequency, numerical probes were placed at 3D downstream, 0.5 D above the centerline, and at 0.5D, spaced along the spanwise direction and the shedding frequencies were obtained from spectra of the axial velocity. Results indicate that the lift for the wire-wrapped cylinder is nearly 150% of that of the smooth cylinder, however, it has a higher drag force. Details of the flow indicate wire-wrapping reduces spanwise coherency and increases the phase angle of vortices, resulting in increased lift. Experimental results indicate a similar trend as the numerical results, with wire-wrapping, reduces the shedding oblique angle and with rotation, reduced peak energy, breaking down the large eddies into smaller eddies of different frequencies.