Abstract

The aerodynamic performance and loading behavior of large- scale wind turbines depend heavily on atmospheric inflow conditions and rotor orientation. While upwind turbines remain the most common design in the industry, recent progress in materials, aeroelastic modeling, and control systems has sparked renewed interest in downwind configurations. This study aims to assess how ABL characteristics and rotor orientation affect the aerodynamic performance of a utility- scale wind turbine. A CFD framework was built in ANSYS Fluent to model the NREL 5 MW Reference Wind Turbine. Transient simulations employed the SST k–ε turbulence model under various inflow conditions: uniform, onshore, and offshore. The study included ABL characterization, grid independence testing, turbulence-model sensitivity analysis, and a comparison of upwind and downwind turbine setups. Initially, rotor-only simulations were conducted to isolate the impact of atmospheric boundary-layer inflow on rotor aerodynamics. Results indicated that uniform inflow produced the highest average thrust of 8.09 × 10⁵ N, while offshore and onshore ABL conditions lowered the thrust to 7.67 × 10⁵ N and 7.47 × 10⁵ N, respectively. Mesh sensitivity tests showed only a 0.3% difference between coarse and refined meshes, confirming numerical convergence. For full turbine simulations, the upwind setup yielded mean thrusts of 7.15 × 10⁵ N and 7.21 × 10⁵ N under onshore and offshore conditions, respectively. Downwind cases resulted in lower mean thrusts of 6.01 × 10⁵ N and 6.29 × 10⁵ N. Compared to upwind operation, downwind configurations exhibited approximately 15.9% and 12.8% reductions in average thrust under onshore and offshore conditions. This decline is mainly due to tower-shadow effects, which periodically diminish the local inflow velocity as the blades pass behind the tower. The findings highlight the importance of realistic ABL modeling for accurate aerodynamic predictions and reveal that rotor orientation influences load variability more than the atmospheric environment. These insights inform the trade-offs involved in designing future large-scale upwind and downwind wind turbines. Future work should extend the present framework to include aeroelastic effects, structural flexibility, and floating offshore platforms for a more comprehensive assessment of next-generation wind turbine designs.

Date of publication

7-2026

Document Type

Thesis

Language

english

Persistent identifier

http://hdl.handle.net/10950/5104

Committee members

Hayder Abdul-Razzak, Shih-Feng Chou, Mohammad Biswas

Degree

Master of Science in Mechanical Engineering

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