Reactive control using an active deformable surface and real-time PIV

This study investigates turbulence control strategies that utilize an active deformable surface and real-time particle image velocimetry (RT-PIV). The control strategies target the sweep and ejection motions of the vortices shed from a spherical cap placed in a laminar boundary layer. The strategies consisted of wall-normal surface deformations that opposed to or complied with the wall-normal (v) or streamwise (u) velocity fluctuations measured using RT-PIV. The results show that the control approach hindered the advancement of sweep motions toward the wall. It also disrupted the periodic shedding of vortices. The v-control with opposing wall motions and u-control with compliant wall motions demonstrated strong inhibition of sweep motions, while the v-control with compliant and u-control with opposing wall motions showed weaker inhibition. All reactive control cases disrupted vortex shedding. In some instances, this disruption was accompanied by increased turbulent kinetic energy due to secondary flow motions. However, the v-control with opposing wall motions reduced the vortex-shedding energy while maintaining total turbulent kinetic energy close to or below that of the unforced flow. Overall, the experiments show the effectiveness of reactive control strategies in inhibiting sweep motions and disrupting vortical structures.