Validation and comparison of turbulence models for predicting wakes of vertical axis wind turbines

Abstract

Vertical axis wind turbine (VAWT) array design requires adequate modelling of the turbine wakes to model the flow throughout the array and, therefore, the power output of turbines in the array. This paper investigates how accurately different turbulence models using 2D computational fluid dynamics (CFD) simulations can estimate near and far wakes of VAWTs to determine an approach towards accurate modelling for array design. Three experiments from the literature are chosen as baselines for validation, with these experiments representing the near to far wake of the turbine. Five URANS turbulence models were chosen due to their common and potential usage for VAWT CFD: models k–ω SST, k–ω SST LRN, k–ω SSTI, transition SST, and k–kl–ω. In addition, the lifting line-free vortex wake (LLFWV) model was tested as an alternative to CFD for the far turbine wake where it was appropriate for use. The results for turbulent kinetic energy and vorticity were compared for the first experiment, whilst streamwise and cross-stream velocity were used for the other two experiments. It was found that none of the turbulence models tested or LLFVW produced adequate estimations within the methodology tested, however, transition SST produced the closest estimations. Further adjustments to the methodology are required to improve accuracy due to their large impact on results including use of 3D CFD, adjustment of surface roughness, and inlet flow characteristics.

Optimized configuration with economic evaluation for shrouded vertical axis wind turbines applicable for urban structures

“…The power coefficient curve for the time step of 0.1°agrees well with the curve with the time step of 0.05°. Moreover, Sahebzadeh et al 78 for two VAWTs and previous studies for a single VAWT 73,79 showed that the time step of 0.1°provides accurate results. Therefore, in the current study, the azimuthal angle increment for all simulations is 0.1°; for the TSR of 2.63, the time step value will be 3.…”

“…Also, by studying different turbulence models, Daróczy et al 72 introduced the SST $$k-\omega $$ model as one that performs well in VAWTs simulations. Also, Barnes et al 73 found that the commonly used SST $$k-\omega $$ model has satisfactory results and faster convergence. The SST $$k-\omega $$ model combines the $$k-\omega $$ model for the boundary layers and the $$k-\varepsilon \,$$model for the rest.…”