Numerical Investigations of a Rotating Wire-Wrapped Cylinder

Abstract

Previous investigations [1–3] on the effects of rotating cylinder with either a smooth surface or cylinders with different surface geometries, placed at either the leading or the trailing edge of a symmetric airfoil on its aerodynamic parameters have shown that rotation at the leading edge does not provide significant lift, while placing the rotating cylinder at the training edge results in more than 20% increase in lift at all angles of attack (AOA) investigated. Increasing the rotation rate (α), the ratio of tangential velocity at the surface of the cylinders (Uτ) to the free stream mean velocity (U∞), increases the lift and grooved cylinders produced more lift than the smooth cylinder. There is an increase in drag when the rotating cylinder is placed at the trailing edge of the airfoil. Here we performed unsteady numerical investigations of a rotating wire-wrapped cylinder, placed in steady flow with α varied between 0 and 2. The free stream mean velocity was constant at 10 m/sec. and the smooth cylinder diameter was 5 cm, which corresponds to an approximate Reynolds number of 3.2 × 104. The wire wrapped had a wire diameter of 5 mm and the ratio of pitch spacing to the cylinder diameter was 1. The wire was wrapped tightly around the entire cylinder. The cylinder has a length to diameter ratio of 20. The rotation rate (α) ranged from 0.5 to 2.0. Results indicate wire-wrapped rotating cylinder produce higher lift than the rotating smooth cylinder and at α equal to 2, the lift for the wire-wrapped cylinder is nearly 150% of the lift of the smooth cylinder. However, wire-wrapped cylinder has higher drag force at higher rotation rate. At α = 2, the lift to drag ratio for the smooth rotating cylinder is 3.89, while the corresponding value for the rotating wire-wrapped cylinder is 3.54. Details of the flow indicates wire-wrapping reduces coherency and increases phase angle of vortices, resulting in increased lift.