Numerical Investigation of the Detaching Vortical Flow at Rotating Cylinders with Thom Discs

Abstract

Due to the high cost pressure in the field of aviation, the further increase in effciency is in the focus of development. Nowadays, airfoils are highly developed and optimized. Thus, new sophisticated approaches, additional configurations and physical effects at lift generation devices have to be explored in order to further reduce drag and significantly increase lift. Focal point of these considerations is the Magnus effect, in which rotating cylinders generate a lift force. This has already been investigated in the past, in particular, different kinds of surface roughnesses, special rotor geometries, ratios of circumferential speed velocity to free stream velocity, or the effect of end plates have been considered. The Scottish engineer A. Thom achieved a significant increase of the performance by adding so called Thom discs coaxially and equidistantly mounted on the cylinder. Investigations of the Thom disc rotors (Thom rotors) have shown a maximum of the lift to drag ratio epsilon for the circumferential cylinder velocity to freestream velocity alpha = 2. Most of the conducted experimental studies have only delivered integral force values. However, detailed insights in the structure of the flow field are still missing.