Research indicates that active control concepts have promise in
mitigating numerous adverse phenomena associated with the aeromechanics
of lifting surfaces. These techniques are being applied to delay stall
of fixed wing aircraft, as well as to eliminate or mitigate vibratory
loads, blade-vortex interaction, and dynamic stall of the flow
about rotorcraft and wind turbine blades. These phenomena are nonlinear
and unsteady for dynamic systems, which add yet another layer of
complexity on the physics of the flow. While a plethora of different
active control techniques is being explored, the use of trailing edge
flaps appears to be one of the more viable and cost-effective concepts.
Static multi-element airfoils and wings have been analyzed
computationally, but little exists on the ability to model these when
the airfoil and flap are dynamic. The costs associated with modeling the
gap between the airfoil and flap have led to approximations where the
flap is modeled only as a morphed tip of the airfoil (no gap). Using a
hybrid Reynolds-Averaged Navier-Stokes/Large-Eddy-Simulation
turbulence technique, an oscillating flapped airfoil has been studied to
determine the influence of modeling the gap on the performance and
acoustic signature of the airfoil. Results are compared with the
experimental data to confirm the validity of the computational approach.
Both attached and separated (dynamic stall) oscillating flows are
examined. The physics within the gap are found to be important for the
airfoil performance when stall is encountered, as well as when acoustic
signatures are required.