Experimental investigation of wake flow characteristics of slotted hollow circular cylinder

This study investigates the wake flow characteristics of slotted hollow circular cylinders at a Reynolds number of 10,000 using particle image velocimetry (PIV) and force measurements. Five different slot configurations are examined in both horizontal (0°) and vertical (90°) orientations. The wake modification mechanisms are investigated through time-averaged flow statistics, proper orthogonal decomposition (POD), and drag coefficient measurements. Horizontal slots introduce jet-wake interactions that progressively alter the wake structure, with a critical transition in flow regime observed at higher slot ratios. POD analysis demonstrates contrasting energy distributions between horizontal and vertical configurations. Reconstructed vorticity fields from POD analysis confirm that horizontal slots disrupt coherent vortex formation via momentum injection, whereas vertical slots accelerate vortex formation near the cylinder base and promote faster wake recovery. The horizontal configuration of slots achieves up to 20.2 % drag reduction and 22.6 % decrease in Strouhal number through vortex suppression. In contrast, for vertical slots, shear layer dynamics is enhanced, leading to more organized yet intensified wake structures, increasing the Strouhal number and drag coefficients. The results reveal distinct wake modification mechanisms between the two orientations and demonstrate that for horizontal orientation, slot-induced jet introduce momentum into the wake, leading to vortex shedding suppression, while vertical slots modify wake dynamics through shear layer disruption, representing distinct flow phenomena of geometric modification. • The influence of slot-induced jet on wake flow characteristics was investigated at Re = 10,000. • Five different slot width ratios in horizontal and vertical orientations were examined. • The slot orientation dramatically modifies the downstream flow structure. • Horizontal slots directly provide additional momentum into the wake. • Vertical slots modify the shear layer dynamics and wake formation process.