Wake-induced vibration suppression for a circular cylinder using a pair of jets

The wake-induced vibration (WIV) presents significant challenges to the structural integrity of multi-cylinder configurations. To effectively alleviate this problem, a numerical simulation is conducted to assess the effect of an active control technique that uses two jets located at the shoulder region of a cylinder to suppress WIV in two-degree-of-freedom. The equations of motion for the WIV response are solved using the Newmark-β method. The Newmark-β method is employed to solve the equations of motion governing the WIV response. Three kinds of angular position (β) on WIV suppression are investigated in detail, including 30°, 60°, and 90°. The angular position β is defined as the angle between the injection angle and the horizontal line. When the angular position (β) is 30°, the maximum cross-flow amplitude ratio (CFAR) is reduced from 0.9 (uncontrolled) to 0.5 (β = 30°), a reduction of approximately 44%. On the contrary, the maximum CFARs remain approximately 1.0 for the case 3 (β = 60°) and case 4 (β = 90°). Especially for the case 4, the cylinder showed the galloping response after the upper branch region. Since the jets are positioned on the vibration cylinder shoulders, the vortexes caused by the jets are opposite to the main vortexes induced by the cylinder. As a consequence, the jets shred the main vortexes in the wake of the cylinder, which leads to the driving force of the vibration reduction. Therefore, the cylinder's WIV amplitude is significantly suppressed.