Comparative Study of Laminar–Turbulent Transition Models for Airfoil Flows at Low Reynolds Numbers
摘要
The demand for predicting accurate flow fields around airfoils at low Reynolds numbers, which involves the laminar–turbulent transition, is increasing owing to growing interest in small unmanned aerial vehicles. However, validation studies of laminar–turbulent transition models at low Reynolds numbers (especially at Re ≤ 50,000) are limited. In this study, we compared transition models in terms of their flow-prediction capabilities related to airfoils at low Reynolds numbers (11,000 ≤ Re ≤ 50,000). We evaluated the capabilities of seven numerical methods: the Menter k–ω shear stress transport model with the γ–Reθt model (SST–γ–Reθt), the Spalart–Allmaras model with the γ–Reθt model (SA–γ–Reθt), the k–kL–ω model, the SA model with the amplification factor transport model (SA–AFT), the transitional SA model proposed by Bas, Cakmakcioglu, and Mura (SA–BCM), the standard SA model without a transition model, and the laminar calculation. The results suggested that explicit formulations of the effects of large-scale vortex behavior and faster activation of incorporated turbulence model are required for better predictability of the low Reynolds number airfoil flows. Overall, the SST–γ–Reθt model exhibited good or fair predictabilities at Re > 23,000 and α > 5°, and the laminar calculation did at Re ≤ 23,000 or α ≤ 5°. The standard SA model presented a notably accurate flow field only when a short laminar separation bubble with very low pressure was formed near the leading edge at α = 8°.