Flow characteristics of a fixed circular cylinder with an upstream splitter plate: On the plate-length sensitivity.

• An upstream splitter plate is used to control the circular cylinder flow. • Vortical structures rolled up on the upstream splitter plate and flow separation change the incoming flow of the cylindrical model. • Drag reduction is generally realized but fluctuating-lift suppression needs to be careful. In the present study, we place a short splitter plate onto the upstream side of a circular cylinder to modify its incoming flow conditions and the wake-vortex patterns and to attenuate the aerodynamic forces. Wind-tunnel investigations are performed at a Reynolds number of Re = 2.66 × 10 4 . Special interests are paid to the length sensitivity of the rigid splitter plate. The 2D particle image velocimetry (PIV) technique is employed to measure the flow patterns around the natural and controlled cylinders to reveal the great modifications of the upstream plate to the cylinder flow. Except for PIV tests, sectional pressure measurements are also conducted to obtain the pressure distribution around the cylinder surface so as to estimate the aerodynamic forces, i.e. drag and lift forces of the natural and controlled cylinders. Results of the surface-pressure measurement demonstrate clearly the control effectiveness and the surrounding flow topologies obtained by PIV system help to uncover the mechanism of the passive upstream-plate control. [ABSTRACT FROM AUTHOR]