Implicit Large Eddy Simulations of Crossflow Instabilities on a Slotted, Natural-Laminar-Flow Airfoil

A low-speed, slotted, natural-laminar-flow airfoil has been tested in the Klebanoff-Saric Wind Tunnel at Texas A&M University. The instigation of crossflow instabilities was the primary focus of the experiment, most notably the wing configurations of Λ = 35° and α = -5.5°, 2.25°. Computations were also conducted using DEKAF to study the linear growth of disturbances measured by integrating the Linear Parabolized Stability Equations (LPSE). N-factor envelopes were established for each instability mechanism. The present work seeks to replicate and validate these results using high-fidelity computational fluid dynamics simulations. The experiments employ the use of both discrete roughness elements on the leading edge, as well as acoustic noise. The OVERFLOW 2.4b overset grid computational fluid dynamics solver is used, with a transitional Reynolds-averaged Navier-Stokes simulation, as well as a time accurate, implicit large eddy simulation. The effect of the crossflow instability on boundary-layer transition is also investigated.