This thesis investigates the aerodynamics of two finite wall-mounted cylinders in tandem, focusing on drag reduction as a function of governing parameters.
For the experimental wind tunnel campaign, two measurement techniques were employed: balance measurements and stereoscopic particle image velocimetry. While balance measurements exhibited good repeatability, drag values obtained with PIV saw high uncertainty and only limited conclusions could be made from it.

Cylinders were mounted to the floor of a closed wind tunnel test section. The trailing cylinder was rigidly attached to the balance underneath, while the leading cylinder could move upstream to the de- sired distance. Stereoscopic PIV images of the wake at various distances upstream and downstream were taken through the transparent sides of the wind tunnel. These images, in combination with the control volume approach, were used to determine the drag of a trailing cylinder.

Coefficients of drag, obtained with a balance for isolated cylinders of various aspect ratios, were in line with similar results from the literature, albeit on the higher side. For cylinders in tandem of the same aspect ratio, AR, as the distance between them increased, the CD of a trailing cylinder converged to that of an isolated cylinder. Comparing tandem configurations with different AR and at the same nondi- mensionalized in-between distance, trailing cylinders with larger AR experienced larger drag reduction.

Introducing cylinder diameter ratio as an additional degree of freedom showed that smaller diameter trailing cylinders experienced greater drag reduction at close distances. However, at a certain distance further downstream, this trend reversed.

The drag reduction values obtained with PIV confirmed the findings from balance measurements. How- ever, due to the limited set of usable data, further work would need to be carried out to gain more confidence in the method.

The cycling industry is influenced by the approval of the tire pressure control system in competitive cycling. This system allows real-time adjustments to the tire-road interaction during races. The total rolling losses is the resistance resulting from tire-road interaction, incorporating resistance due to tire deformation and the dissipation of vibrational energy within the rider-bicycle system. This research investigates the influence of tire parameters on the total rolling losses during road cycling through three key measurements: ink print test, drum test, and rolling losses measurement. The ink print test captures the contact area between the tire and road surface under specified loads, revealing significant impacts of tire type, width, inflation pressure and vertical load on the contact patch shape. In addition, this study shows that an increase in contact patch measures is related to an increase in the rolling resistance coefficient (𝐶𝑟𝑟). The drum test extracts 𝐶𝑟𝑟 values related to pure rolling resistance by measuring the power needed to maintain constant velocity of a rotating drum when in contact with a loaded tire. Results indicate a significant influence of tire type, width, inflation pressure, vertical load and velocity on 𝐶𝑟𝑟 estimates. Combining 𝐶𝑟𝑟 obtain with drum testing with 𝐶𝑟𝑟 determined with total rolling losses measurements, provides insights into the contribution of vibrational losses to the total rolling losses. The study employs a novel bike trailer measurement technique to estimate total rolling losses, measuring the cyclist’s power while cycling at constant speed with elimination of aerodynamic drag. Despite some limitations, the bike trailer method successfully identifies optimal tire parameters
for minimizing rolling losses on different road surfaces at varying speeds.