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The aerodynamic performance of the flow around a cylinder with two free ends, which is also referred to as a finite-length cylinder, continues to be a subject of rigorous academic inquiry. However, limited research has been conducted on finite-length cylinders with rough surfaces. To evaluate the impact of relative roughness on the aerodynamic performance of a finite-length cylinder, we performed numerical simulations on a cylinder model with an aspect ratio of 1.5 with various relative roughness values. These simulations covered a range of Reynolds numbers from 3.9 × 103 to 4.8 × 105. The results indicated that both the relative roughness and Reynolds number could affect the aerodynamic characteristics of the cylinder by altering the flow pattern around the cylinder. As the Reynolds number increased, the four spiral eddies behind the finite-length cylinder gradually lost their symmetry in the axial direction and eventually transformed into a pair of recirculating eddies. Moreover, when the Reynolds number was constant at 2.0 × 104, an increase in the surface roughness of the cylinder triggered the same phenomenon. Additionally, the mechanism by which the surface roughness affected the aerodynamic coefficient of a finite-length cylinder in the current Reynolds number range was revealed. This influence was mainly attributed to the impact of pressure on the backside of the cylinder. [ABSTRACT FROM AUTHOR]

The aerodynamic performance of the flow around a cylinder with two free ends, which is also referred to as a finite-length cylinder, continues to be a subject of rigorous academic inquiry. However, limited research has been conducted on finite-length cylinders with rough surfaces. To evaluate the impact of relative roughness on the aerodynamic performance of a finite-length cylinder, we performed numerical simulations on a cylinder model with an aspect ratio of 1.5 with various relative roughness values. These simulations covered a range of Reynolds numbers from 3.9 × 103 to 4.8 × 105. The results indicated that both the relative roughness and Reynolds number could affect the aerodynamic characteristics of the cylinder by altering the flow pattern around the cylinder. As the Reynolds number increased, the four spiral eddies behind the finite-length cylinder gradually lost their symmetry in the axial direction and eventually transformed into a pair of recirculating eddies. Moreover, when the Reynolds number was constant at 2.0 × 104, an increase in the surface roughness of the cylinder triggered the same phenomenon. Additionally, the mechanism by which the surface roughness affected the aerodynamic coefficient of a finite-length cylinder in the current Reynolds number range was revealed. This influence was mainly attributed to the impact of pressure on the backside of the cylinder. [ABSTRACT FROM AUTHOR]