Abstract
Wind energy is an important contributor to the generation of electricity amongst the renewable sources, and per long-term political goals it is expected that this contribution will be further increased. For achieving this goal, optimized blades having increased aerodynamic performance must be designed especially for small horizontal wing turbines (SHWT). SHWT are exposed to a highly volatile, low Reynolds number, turbulent flow, where not only boundary layer transition phenomena are significant, but additionally, 3D flow effects are dominant, due to the relatively small length of the wind turbine blades. These blades are usually 1.5 to 3.5 m in diameter and produce 1 - 10 kW of electricity at their optimum design conditions which are closely related to the wind speed. In order to maximize the wind turbine blades efficiency, a thorough analysis of the complex aerodynamic effects that govern the flow has to be performed. In the current paper an assessment of the modelling of a wind turbine blade profile of a SHWT is investigated, with the use of Computational Fluid Dynamic (CFD) and validated with appropriate experiments. More specifically, a characteristic profile of an operating SHWT blade is selected and carefully picked transitional turbulence models are utilized for the CFD computations, for a wide range of angles of attack (AoA). The selected models are the 4-equation SST k-? turbulence model of Menter et al. (1994) and the turbulence model of Walters and Cokljat (2008) that adopts the laminar kinetic energy concept. Two relatively small Reynolds numbers are chosen for studying the flow, in order to take into account, the transient and complex flow phenomena that are present in real wind turbine operating conditions. For the validation of the computational results, existing literature data (Selig and McGranahan, 2004) are used in combination with the acquired experimental data from the appropriately designed experiments which were performed in the Laboratory of Fluid Dynamics and Turbomachinery (LFMT) facilities. The results show the existing potential of further optimizing the wind turbine blades and as a result enhancing their aerodynamic performance and efficiency.
