Clockwise Vortical-Gust/Airfoil Interactions at a Transitional Reynolds Number

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Clockwise Vortical-Gust/Airfoil Interactions at a Transitional Reynolds Number

Barnes, Caleb J. / Visbal, Miguel R.

This paper presents high-fidelity implicit large-eddy simulations (ILES) of parallel vortical gust interactions with a NACA0012 airfoil operating at a transitional chord-based Reynolds number of ${R e}_{c} = 200, 000$ and an angle of attack of $α = 4 \deg$ . The gust is supplied upstream of the airfoil as a Taylor vortex. Three different initial vertical positions are considered for a clockwise (CW)-oriented gust. ILES simulation of CW gust interactions is compared with inviscid simulations as well as prior counterclockwise (CCW) gust simulations. Contrary to the previous CCW gust interactions, the upper surface boundary-layer experiences an upstream excursion of laminar separation, transition, and turbulent reattachment that lingers behind the gust. This upstream shift manifests in a pitch-up moment coefficient that relaxes slowly to the pregust state. As in the previous CCW cases, the lower surface boundary layer is disrupted by the CW vortex producing a brief acoustic event. This effect is particularly severe when the CW gust passes just beneath the wing section. In this scenario, the lower surface instability coalesces into a boundary-layer vortex and briefly forms a dipole with the CW gust.