  Mixed Convection inside a cavity resulting from thermal buoyancy force under
local modulation via rotating flat plate has been investigated. The present
model consists of a square cavity with the left and right vertical walls fixed
at constant high and low temperatures respectively while the top and bottom
walls are supposed to be adiabatic. Two clockwise rotating flat plates, having
negligible thickness in comparison to their lengths, acting as flow modulators
have been placed vertically along the centerline of the cavity. The moving
boundary problem due to plate motion in this study has been solved by
implementing \textit{Arbitrary Lagrangian Eulerian (ALE)} finite element
formulation with triangular discretization scheme.Simulations are conducted for
air ($Pr=0.71$) at different Rayleigh numbers ($10^2 \leq Ra \leq 10^6$).
Rotational Reynolds number based on plate dynamic condition has been considered
to be constant at 430. Numerical results identify critical Rayleigh number
$Ra_{cr}=0.41\times10^6$ beyond which two smaller flow modulators are more
effective than a single larger modulator. Thermal oscillating frequency was
observed to be insensitive to Rayleigh number for the case of double
modulators.
