Effects of splitter plates and Reynolds number on the aerodynamic loads acting on a circular cylinder

• Flat-plate turbulent boundary layer generated by frontal splitter plate has produced a postcritical flow at relatively low Reynolds numbers.
• Vortex shedding can be suppressed by a splitter plate in the wake.
• The semi-cylindrical roof can approximated as a circular cylinder with bilateral plates under similar flow conditions.
• The transitional Re range of the semi-cylindrical roof was identified in between 6.90×104 and 1.66×105.

Many studies have been undertaken aimed at reducing drag forces and suppressing vortex shedding from circular cylinders, mainly focusing on the influence of the splitter plate in the wake of the airflow. In this study, a circular cylinder with diameter D (0.4 m) with splitter plates has been used to investigate the aerodynamic differences between a bare cylinder and a semi-cylindrical roof. Wind tunnel experiments, with simultaneous multi-pressure measurements on cylinders with frontal, wake and bilateral splitter plates, have been undertaken for a range of Reynolds numbers from 6.90×104 to 8.28×105. It was found that a frontal splitter plate, with plate length to cylinder diameter ratio of L/D=3, has produced a postcritical flow at relatively low Reynolds numbers by the generated disturbances in the approaching flow. For the semi-cylindrical roof, that can be approximated as a circular cylinder with bilateral plates under similar flow conditions, the vortex shedding is suppressed by a splitter plate (L/D=3) in the wake. The results reveal that the transition of separated shear layer around a semi-cylindrical roof occurs in the Reynolds number range 6.90×104 to 1.66×105. The mean and fluctuating pressure distributions become relatively stable when Re>1.66×105.