DNS Dataset of a Thick Symmetric Airfoil at Low Reynolds Number: NACA ۰۰۱۸ with LES Comparison

This study examines the aerodynamic behavior of the symmetric National Advisory Committee for Aeronautics (NACA) ۰۰۱۸ airfoil at a chord-based Reynolds number of ۳۰,۰۰۰, utilizing Direct Numerical Simulation (DNS) as the primary tool, supplemented by selected Large Eddy Simulation (LES) cases. DNS covers a full sweep of angles of attack from ۰° to ۱۰°, while LES was conducted at α = ۴° and ۸° to verify consistency between the two approaches. Despite the limited LES dataset-restricted by computational cost, the results showed nearly identical aerodynamic loads and surface pressure distributions, thereby reinforcing confidence in the DNS database. To further assess robustness, two additional DNS cases were performed for the NACA ۰۰۱۲ airfoil at α = ۳° and ۶° under identical grid resolution and flow conditions. These simulations demonstrated very good agreement with published experiments, extending validation beyond a single geometry. In both DNS and LES, clean inflow conditions were imposed, ensuring that the domain inlet did not introduce resolved turbulence. The results captured laminar boundary-layer separation on the suction side without reattachment, producing bluff-body-like wake dynamics dominated by periodic vortex shedding, while classical Kelvin–Helmholtz instabilities were not significant. Computed aerodynamic coefficients, including time-averaged lift, showed good agreement with measurements. The novelty of this work lies in providing the first DNS dataset for a thick symmetric airfoil (NACA ۰۰۱۸) at Re = ۳۰,۰۰۰, further validated through NACA ۰۰۱۲ comparisons. The findings establish a benchmark for future investigations of unsteady aerodynamics, particularly dynamic stall in pitching motions, and are directly relevant for the design of low-Reynolds-number devices such as micro air vehicles, unmanned aerial vehicles, and vertical-axis wind turbines.

کلیدواژه ها:

NACA ۰۰۱۸ airfoil ، Low Reynolds Number flow ، Direct Numerical Simulation (DNS) ، Large Eddy Simulation (LES) ، Boundary layer separation