This study investigates the influence of the spanwise periodic domain length Lz on the accuracy of numerical simulations of flow past an SD7003 airfoil (Selig–Donovan series) in post-stall conditions at an angle of attack α=14° and Reynolds number Rec=60 000. Large eddy simulations and direct numerical simulations are performed for spanwise extents ranging from Lz/c=0.2 to 2.0 to evaluate their impact on flow dynamics, aerodynamic forces, and wake characteristics. The results demonstrate a strong sensitivity of key flow features and aerodynamic coefficients to the chosen spanwise length. Domains that are too short artificially constrain three-dimensional flow structures, leading to significant overprediction of drag, lift, and unsteady lift fluctuations. This behavior is attributed to trailing-edge flow structures being forced into an unrealistically coherent spanwise configuration, which inhibits their natural three-dimensional breakdown in the wake. Analyses based on two-point correlations and flow statistics indicate that a minimum spanwise length of Lz/c≥0.8 is necessary to capture the largest turbulent scales, reduce the influence of periodic boundary conditions, and obtain accurate predictions of unsteady aerodynamic forces. The findings further suggest that previous high-fidelity studies, which used Lz/c=0.2 for computational efficiency, were insufficient to represent the full three-dimensional complexity of post-stall flow.
Montalà et al. (Wed,) studied this question.