Surface Roughness and Trip Effects for a Circular Cylinder at Subcritical Reynolds Numbers

Aerodynamic drag is the major source of resistance experienced by athletes in activities such as road cycling. Over bluff bodies, which is how an athlete is typically modelled, passive flow control methods such as surface roughness and boundary layer tripwires appeared to be particularly relevant in transitioning the local boundary layer at the surfaces to turbulence, resulting in a lower drag at smaller Reynolds numbers. In the experimental study, a cylindrical model equipped with textiles and tripwires that had 2D and zigzag geometries were connected to a custom force balance to understand the effects of these surface modifications on the drag. The primary objective of the present work is to explore the effects of drag reduction when fabrics with multiple number of seams and tripwires are attached on a cylinder at different angles from the stagnation point. Utilizing these flow control methods can provide potential time gains for a cyclist.