Fluid–structure interactions are widely seen in engineering. For example, when flow blows over a slender
structure (off-shore structures, high-rise buildings, cable-stayed bridges, and fluid machinery, etc.), vortices
separate alternately from the structure, giving rise to excitation forces and causing the structure to vibrate [1].
The structural motion in turn influences the flow field, resulting in a highly nonlinear fluid–structure coupling
[2,3]. This type of fluid–structure interaction may affect the fatigue life of engineering structures and even lead
to structural damages and serious accidents, and has become one of the major concern in many applications.
Furthermore, vortex shedding is responsible for noise generation in case the kinetic energies of vortical
motions are converted into the acoustic wave involving the longitudinal oscillation of fluid particles [4].
Therefore, the control of flow and its induced structural vibration has attracted the interests of many
researchers for many years.
A variety of control techniques have been developed in the past, and may be passive and active. The passive
technique requires no external energy, producing desired effects on flow by changing structural geometries,
adding grooves, shrouds or near-wake stabilizers to structures [5,6]. The active technique involves energy input
via the use of actuators to bring about desirable changes to the fluid–structure system using either an
independent external disturbance, i.e. the open-loop control, or a feedback system, i.e. the closed-loop control.
Most of previous active control techniques aimed at controlling vortex shedding. Blevins [7] explored the
influence of a transverse sound wave on vortex shedding from a cylinder at a Reynolds number
Re ¼ 2–4104, based on the free-stream velocity and the characteristic height of the cylinder. The acousticwave was emitted from two loudspeakers mounted on the two sides of a wind tunnel test section. It was found
that the sound introduced could increase the coherence of vortices along the cylinder axis and cause vortex
shedding to be locked on with the excitation acoustic wave. Inspired by this work, Roussopoulos [8] and
Ffowcs-Williams and Zhao [9] used a closed-loop method with the feedback signal from a hot wire to drive
loudspeakers. The acoustic excitation from the loudspeakers suppressed vortex shedding from a cylinder at
Re ¼ 120 and 400, respectively. Another approach is to control the rollup motion of shear layers separated
from a cylinder by oscillating or rotating the cylinder. Using this technique, Warui and Fujisawa [10] and
Tokumaru and Dimotakis [11] effectively reduced the vortex strength using electromagnetic actuators. The
actuators were mounted at both ends of a circular cylinder to create a cylinder motion and controlled by a
feedback signal from a hot wire placed in the wake (ReE104). Williams et al. [12] introduced both symmetrical
and anti-symmetrical forcing into a cylinder wake (Re ¼ 470) at a frequency of about twice the vortex
shedding frequency (fs) through two rows of holes located at 7451, respectively, away from the forward
stagnation line of the cylinder. They managed to modify fs and the vortex street. Baz and Kim [13] and Tani
et al. [14] used piezo-ceramic actuators installed inside a cantilevered cylinder to exert a force on the cylinder.
The actuators were excited by a feedback signal measured from the structural vibration, thus increasing the
damping of the cylinder and effectively reducing the structural vibration at the occurrence of resonance
(Re ¼ 17,160–26,555), when fs coincided with the natural frequency, f 0n, of the flow–structure system.
Cheng et al. [15] proposed a new technique by creating a local perturbation on one surface of a square
cylinder in a cross flow using piezo-ceramic actuators. They demonstrated that this perturbation could
manipulate fluid–structure interactions, suppressing (or enhancing) vortex shedding and/or flow-induced
structural vibration, and even reducing noise. Both open- and closed-loop control have been investigated. In
this review, we will focus on this technique and its development, summarizing the technique itself,
applications, performances and physical mechanisms. The technique is first introduced in Section 2. Various
applications based on this technique are then given in Section 3, and mechanisms behind the control are
discussed in Section 4. A brief summary is given in Section 5.