As a passive flow controller, a circular cylinder is commonly employed in airborne optical systems to disturb the incoming flow and thereby mitigate aerodynamic interference with optical components. Under near-wall constraints, the spacing between the cylinder and the wall exerts a significant influence on several flow characteristics, including wake deflection angle, aerodynamic forces, trajectory, and vortex structures. In addition, the density gradient variation within the wake can further deteriorate the aero-optical performance, thus degrading beam propagation quality. To address these issues, this study employs numerical simulations combined with proper orthogonal decomposition to systematically investigate the effect of the spacing ratio between the cylinder and the wall (G/D) on wake flow characteristics. Based on the ray-tracing method, the corresponding aero-optical effects induced by wake variations are also analyzed. Furthermore, two modified cylinder configurations, a cylinder with a slit and another with a splitter plate, are proposed to suppress wake deflection and its aero-optical effects. Results show that under the optimal configuration, the wake deflection angle decreases by approximately 6°, while the OPDrms,max and OPDrms,mean values are reduced by 70% and 35%, respectively.
Zhang et al. (Wed,) studied this question.