Cfd modelling of h-darrieus vertical axis wind turbine

2.2 COMPUTATIONAL FLUID DYNAMICS SIMULATION 
2.2.1 Considering Different Turbulence Models 
Many turbulence models are developed and still are studied for improvements to capture the 
complex and unruly behaviour of the turbulence.
Rezaeiha, Montazeri, and Blocken [41] compared commonly used seven turbulence models of 
eddy-viscosity for the simulations of VAWT in CFD. The models include one to four equations, viz. 
the realizable k-ε, Spalart-Allmaras, RNG k-ε, SST k-ω, SST k-ω with an additional intermittency 
transition model (SSTI), transition SST (TSST) k-ω models and k-kl-ω models. Besides, the 
comparison includes the inviscid modeling. The blade aerodynamics, turbine power performance, 
and turbine wake, are all being studied. Incompressible unstable URANS simulations with high 
fidelity were used. By analysis, it is seen that the simulation results are highly sensitive to the 
turbulence model which is particularly true for the CP turbine power coefficient. The k-kl-ω models, 
SA inviscid, RNG k-ε, and realizable k-ε all fail to reproduce the aerodynamic performance of 
VAWT, according to the findings. Only SST type models (TSST, SSTI, and SST k-ω) demonstrate 
rational compromise with all experimental data, with the transitional SST k-ω types (SSTI and 
TSST) recommended, particularly in the transitional flow regime. 
In this study, the transition SST model was used for 2D simulation of H-Darrieus VAWT. 
2.2.1.1 k-ε model 
Daróczy et al. [42] have studied different turbulence models for the simulation of H-Darrieus 
turbine. By comparing with experimental results, it was found that the k-ε and k-ω SST model 

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showed better results for 2D simulation.
Howell et al. [43] applied the k-ε for both 2D and 3D simulations and it was observed that, while 
better results were obtained in 3D simulation, the k-ε model overestimated the performance 
coefficient in 2D simulation.
Untaroiu et al. [44] employed the standard k-ε model to study the self-starting behaviour of H-
Darrieus turbine in both 2D and 3D simulations where both failed to estimate the behaviour, 
especially the 3D simulation. So, it was recommended not to use this model to estimate the self-
starting behaviour of VAWT, and mainly not for 3D simulations.