Flow characteristics and passive flow control of circular cylinders with triangular vortex generators: An experimental investigation

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Optimizing flow patterns around cylinders is crucial for diverse engineering applications, aiming to mitigate vibrations induced by vortex shedding and minimize drag. Strategies, such as the implementation of vortex generators and modifications in the cylinder's surface geometry, are explored to optimize flow patterns and enhance the performance of structures exposed to fluid dynamics. This study investigated the flow characteristics of a smooth circular cylinder and cylinders equipped with triangular vortex generators placed at different position angles (α=15°, 30°, 60°, and 75°) and yaw angles (β=30°, 45°, 60°, and 75°) at the surface. The particle image velocimetry technique is used to measure the instantaneous and time-averaged velocities of the fluid flow over cylinders at Reynolds Number 8000. It is found that flow characteristics are highly dependent on the position angle of the triangular vortex generators. Specifically, at α=30° and β=60°, a substantial reduction of 17.3, 10.3, and 19.5 % occurred in normalized streamwise and root mean square of cross-stream velocity fluctuations and turbulent kinetic energy values, respectively, in comparison to that of the smooth circular cylinder. Furthermore, a noteworthy drag reduction of 33.3 % was achieved in the case of α=30° and β=60° through the elongation of the recirculation length and the establishment of a low-pressure zone away from the base of the circular cylinder. On the other hand, the lowest Strouhal number is obtained as 0.180 in the case of α=75° and β=30° where it was 0.211 at the smooth CC case. As a result, triangular vortex generators with an area of 1.1% of the total side projection area of the cylinder were found to be very effective in flow control.