A	amplitude
$Be$	Bejan number
$C_p$	specific heat capacity
$d_f$	diameter of the base fluid molecule
$d_p$	diameter of the nanoparticle
g	gravitational acceleration
GEG	Dimensionless global entropy generation
H	dimensionless length of the heat source, $H=h/L$
k	thermal conductivity
$K_r$	inner block to nanofluid thermal conductivity ratio, $K_r=k_s/k_{nf}$
L	width and height of the square cavity
N	number of undulations
$N_{\mu }$	irreversibility distribution ratio
$\overline{Nu}$	average Nusselt number
Pr	Prandtl number
r & R	radius of rotating cylinder & dimensionless radius of rotating cylinder
$Ra$	Rayleigh number
$S_{\mathrm{gen}}$	Entropy generation rate
$S_{\mathrm{GEN}}$	Dimensionless entropy generation rate
$S_{\theta }$	dimensionless entropy generation due to heat transfer irreversibility
$S_{\mathsf{\Psi }}$	dimensionless entropy generation nanofluid friction irreversibility
${\mathrm{Re}}_B$	Brownian motion Reynolds number
T	temperature
$T_0$	reference temperature (310 K)
$T_{fr}$	freezing point of the base fluid (273.15 K)
$\mathbf{v}$, $\mathbf{V}$	velocity and dimensionless velocity vector
$u_B$	Brownian velocity of the nanoparticle
x, y & X, Y	space coordinates & dimensionless space coordinates
Greek symbols
$\alpha$	thermal diffusivity
$\beta$	thermal expansion coefficient
$\delta$	normalized temperature parameter
$\theta$	dimensionless temperature
$\mathsf{\Theta }$	dimensionless length of the surface of the cylinder
$\mu$	dynamic viscosity
$\nu$	kinematic viscosity
$\rho$	density
$\varphi$	solid volume fraction
$\omega ,\mathsf{\Omega }$	angular rotational velocity, dimensionless angular rotational velocity
Subscript
b	bottom
c	cold
f	base fluid
h	hot
$nf$	nanofluid
p	solid nanoparticles
s	solid cylinder