Coupling between vortex flow and whisker sensor in cylinder wakes with time-varying streamwise gaps

The flow-induced vibration of a whisker in the wake of a movable circular cylinder with time-varying streamwise gaps is experimentally investigated to understand how whiskers detect variations in the swimming status of an upstream target. The results show that whisker sensitivity to gap growth rates gradually decreases when such growth rates become sufficiently high, regardless of initial gaps. From the integrated experimental measurements and theoretical model, the reduction of whisker sensitivity under high gap growth rates can be attributed to sufficiently strong vortices initiated by fast movement of the upstream cylinder, which compensate vortex strength decay due to the gap growth.