02693nam a22001577a 4500 621 Mir Afzal, 130446 Experimental Investigation of Vortex Induced Vibration Piezoelectric Energy Harvester using Dimpled Structure / Mir Afzal Islamabad : SMME- NUST; 2025. 74p. Soft Copy 30cm The growing demand for sustainable energy solutions for autonomous IoT sensors and remote monitoring devices has driven interest in piezoelectric energy harvesting from ambient fluid flows. This study investigates wake-induced vibrations from PVDF piezoelectric flags positioned behind dimpled circular cylinders compared to smooth baseline configurations. Comprehensive water tunnel experiments tested a 25 mm diameter cylinder at flow velocities of 0.15-0.30 m/s (Reynolds numbers 3500-11500). Nine dimpled configurations were evaluated, featuring three dimple diameters (9, 11, and 13mm) arranged in 3, 4, and 5 columns. Flag was positioned at streamwise gaps of 1D3D downstream. Data acquisition included real-time measurements of voltage, high velocity analysis of video, and Particle Image Velocimetry (PIV) for wake characterization. Smooth circular cylinders significantly outperformed all dimpled configurations and achieved peak power output of 15.2 μW at 2D spacing and 0.30 m/s, maintaining optimal wake width. Performance degraded systematically among dimpled configurations: 3-column arrangements outperformed 4-column designs, which exceeded 5-column configurations, while smaller dimples consistently outperformed larger ones. The best dimpled cylinder (3-column, 9mm dimples) achieved only 91.45% of smooth cylinder performance, while the worst configuration (5-column, 13mm dimples) delivered merely 59.41% of baseline output. PIV analysis revealed dimple-induced boundary layer energization promotes premature flow reattachment, reducing wake width and vortex formation length, thus diminishing downstream energy availability. Optimal energy harvesting occurs at 1.5D-2.5D spacing, peaking at 2D regardless of configuration. These findings provide critical design guidance for marine sensors, structural health monitoring, and autonomous underwater vehicles, demonstrating that smooth cylinders optimize VIV energy harvesting. This research advances understanding of fluid-structure interactions in energy harvesting and provides practical guidelines for sustainable micro-power generation systems. MS Mechanical Engineering Supervisor : DR. EMAD UD DIN 119531 http://10.250.8.41:8080/xmlui/handle/123456789/54443 ddc THE 614607 614607 0 0 0 0 SMME SMME EB 2025-09-01 0 621 SMME-TH-1147 2025-09-01 2025-09-01 THE