Mesh and model requirements for capturing deep-stall aerodynamics in low-Mach-number flows

Journal Article · Wed Jun 14 00:00:00 EDT 2023 · Journal of Turbulence (Online)

DOI:https://doi.org/10.1080/14685248.2023.2225141· OSTI ID:1992015

Bidadi, Shreyas ^[1]; Vijayakumar, Ganesh ^[1]; Sharma, Ashesh  ^[1]; Sprague, Michael A.  ^[1]

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1. National Renewable Energy Laboratory (NREL), Golden, CO (United States)

Here, this work presents a comprehensive computational fluid dynamics investigation of the effects of grid resolution and turbulence-model choice for capturing the unsteady three-dimensional aerodynamic performance of NACA 0012 and 0021 airfoils, with specific focus on the deep-stall regime. At high angles of attack (α), wind turbine blades routinely experience vortex-induced vibrations, which can cause significant structural damages. Accurate predictions of post-stall aerodynamics can identify the frequencies at which such vibrations maybe triggered. In this context, the NACA 0012 airfoil simulations are conducted at a chord-based Reynolds number, Re_c=2×10⁶, with the k-ω Shear-Stress Transport Reynolds-Averaged Navier-Stokes (RANS) and Improved Delayed Detached Eddy Simulation (IDDES) hybrid RANS-Large Eddy Simulation turbulence models. The effect of mesh resolution both in the wall-normal and spanwise directions is investigated. Only the IDDES model with a minimum spanwise resolution of 24 cells per chord length correctly predicts the aerodynamic forces. Spectral analysis shows the peak primary shedding frequency at α=30°, which signifies the end of the stall region. In the post-stall regime, both lift and drag frequencies drop asymptotically with increasing α. The Strouhal number, based on normalised chord length, remains nearly constant in this region. Based on this study, NACA 0021 airfoil runs are performed with IDDES for Re_c=2.7×10⁵ and 2.0×10⁶ on the finest wall-normal mesh and three spanwise grids. Simulations conducted on the finer spanwise grids demonstrate grid independence and show good agreement with experiments. The effect of varying Rec on the airfoil frequency statistics is investigated. Additionally, comparison studies are presented to investigate the impact of airfoil thickness on the frequency content at Re_c=2.0×10⁶. The results from the study provide guidance on the choice of mesh resolution with the IDDES model to accurately capture aerodynamic quantities for complex industrial applications.

• Research Organization: National Renewable Energy Laboratory (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Wind Energy Technologies Office; USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR)
• Grant/Contract Number: AC36-08GO28308
• OSTI ID: 1992015
• Report Number(s): NREL/JA-5000-84751; MainId:85524; UUID:2546e9f9-e575-4a4d-8a5b-182d0e6cacef; MainAdminID:69370
• Journal Information: Journal of Turbulence (Online), Vol. 24, Issue 8; ISSN 1468-5248
• Publisher: Taylor & Francis
• Country of Publication: United States
• Language: English

Related Subjects

97 MATHEMATICS AND COMPUTING
17 WIND ENERGY
airfoil
deep stall
IDDES
RANS
wind turbine