Lift Force Generation of a Moving Circular Cylinder with a Strip-Plate Set Downstream in Cruciform Arrangement: Flow Field Improving Using Tip Ends

A new concept of generating steady lift on a circular cylinder in uniform flow has been developed. A strip plate is placed behind a cylinder in cruciform arrangement with a suitable gap for employing the longitudinal vortex (LV). When the upstream cylinder moves parallel to the strip plate, the LV appears behind the moving cylinder near the crisscross region. The steady lift is produced by the aerodynamic effect of the vortex-induced suction flow. The vortex regime has a limited area, and the exterior is dominated by the wake which generates the negative driving force due to the drag. In this study, the negative portion near both free ends of the original cylinder was examined and restrained by attaching tip-end configurations for improving the flow field. Two types of added tip ends were evaluated that included the circular endplate and the semi-circular plate with a rectangular-shape bend. The unsteady Reynolds-averaged Navier-Stokes (URANS) simulation was employed. The numerical results were validated by the experimental data. The numerical investigation indicated that a negative lift is generated near the cylinder ends. When the accessory tip ends were employed, the semi-circular plate with a bend can suppress the disturbed flow and produce a positive lift, whereas only the circular endplate cannot.