Numerical investigations of three-dimensional flows around a cylinder attaching with symmetric strips

Abstract

Minor changes to the surface of a cylinder can significantly influence the associated flow characteristics. This paper describes a three-dimensional numerical investigation of a cylinder attached with symmetric strips in a uniform flow at R e = 3900. The location (20 ° ≤ α ≤ 130 °), thickness (0.01 D ≤ t ≤ 0.08 D), and coverage (5 ° ≤ β ≤ 100 °) of the strips are selected for study. Two flow modes, patterns A and D, can be characterized in the flow around this passive turbulence control cylinder by their vortex enhancement and suppression effects. The Strouhal number of pattern A is very close to the response of a smooth cylinder. For cylinders with the upper strip located at α ≤ 90 ° from the front stagnation point, the lift force correlation in the spanwise direction is enhanced by the forced flow separation. When the front edge of the upper strip is fixed at α = 60 °, the thickness of the strips plays a vital role: the drag and lift force increase linearly as the thickness increases, whereas the Strouhal number and the vortex shedding frequency decrease.