Numerical simulations of vertical axis wind turbines using different turbulence models

Vertical axis wind turbines (VAWTs) are promising candidates for wind energy harvesting in the urban environment. However, their aerodynamic performance still falls behind of their horizontal axis counterparts. This could be associated with the comparatively small research they have received in the past decades as well as their complex unsteady aerodynamics. Computational Fluid Dynamics (CFD) has been widely used to evaluate and improve the aerodynamic performance of VAWTs. An extensive literature study reveals that the 2D unsteady Reynolds-Averaged Navier-Stokes (URANS) approach has been used in the majority of CFD studies on VAWTs while the sensitivity of the CFD results to the choice of the turbulence model has not yet been comprehensively investigated in the literature. Therefore, the current study intends to evaluate the aerodynamic performance of three different VAWTs, calculated using 2D URANS with seven different one- to four-equation turbulence models, namely Spalart-Allmaras, RNG and realizable k-ε, k-ω SST, kωSSTi (with the intermittency model), k-kl-ω and transition SST. The results are also compared against inviscid simulations. The turbines are selected based on the availability of the experimental data for the comparison in addition due to their geometrical and operational differences which would help to further generalize the conclusions. A comparative analysis of the turbine power performance and wake velocities for the turbines indicates that the 3-equation k-kl-ω and the 4-equation transition SST models are the two best-performing models while the inviscid modeling and the ε-based models exhibit the worst performance for CP predictions in comparison to the experiment. The findings support more accurate CFD simulations of VAWTs.