Symbol	Description
A	Circle plate (leaf) cross-sectional area
Ab	beam cross-sectional area
Cp	Capacitance of the PZT
Cf	Piezoelectric coupling coefficient
$\mathit{E}$	Young’s modulus of the elastic beam
F	Slapping force (acting on the root of the main structure)
Fb	Wind force acting on both the circular plate and the rectangular plate.
$\mathit{I}$	Beam area moment of inertia
${\overline{I}}_A$	Dimensionless mass moment of inertia of the circle plate (leaf)
${\overline{I}}_b$	${\displaystyle \frac{m_b{y}^2}{m_b{l}^2}}$ Dimensionless beam mass moment of inertia
$\mathit{l}$	Length of beam
$\overline{M}$	Mass ratio of the circle plate to the beam
mb	beam mass
q	distributed external force
$\overline{q}$	Dimensionless distributed external force
T	Slapping period
$\overline{T}$	Dimensionless slapping period
t	Dimensional time
V	Voltage
${\alpha }_n$	Eigenvalue of nth mode
$\epsilon$	Time scale of small perturbations.
$\eta$	Von Kármán nonlinear strain
${\mu }_w$	Dimensionless damping coefficient
$\xi$	Generalized coordinate (time-dependent variable)
$\nu$	Dimensionless voltage
$\mathsf{\rho }$	Density
$\tau$	Dimensionless time
${\varphi }_n$	Mode shape of nth mode
$\sigma$	Tuned frequency
${\zeta }_n$	The nth mode phase
${\mathsf{\omega }}_{\mathit{n}}$	Natural frequency of nth mode