Cfd modelling of h-darrieus vertical axis wind turbine

2.1.2 Vortex Model 
Strickland, Webster, and Nguyen [36] developed an aerodynamic prediction model for two-
dimensional and three-dimensional Darrieus turbines where they have used vortex lattice method of 
analysis. A number of experiments were conducted in a water tow tank on several two dimensional 
setups of rotor. In general, there was a good match found between the experiments and analyses 
conducted. To analyze the near wake flow behind the rotors and to estimate instantaneous 
aerodynamic forces of blades, this model can be utilized. However, long computational time is 
required for the vortex model. As a results, instead of the long time consuming vortex models, most 
of the time the much simpler momentum model is used when only rotor power coefficient is 
required to be calculated. Often, additional work is required to be done in order to reach a periodic 
solution to reduce the high calculation time needed by the vortex model. 
Wang, Zhang, and Zeng [37] validated a prospective flow 2-D vortex panel model of the straight 
blade vertical axis turbine with variable pitch for the calculation of unsteady hydrodynamics for the 
energy conversion of tidal streams. From this study, it was seen that the numerical results of 
predicted wake flow of the rotor and instantaneous blade forces showed a good accordance with that 
of the test data. The previous standard free vortex model as well as vortex method combined with 
finite element analysis was also compared which showed that the 2D vortex panel model was far 
better than that of the previous mode yet less complicated than that of the latter one and appropriate 
for optimization as well as designing of the VAWT with straight blades. 

---

16 
2.1.3 Cascade Models 
Hirsch and Mandal [38] first applied the cascade model to VAWT. This model is not seeming to be 
applied widely in the literature. Overall, the performance of this model is satisfactory and unlike the 
streamtube model, it does not have any problem with convergence. Hand and Cashman [39] and 
Hand, Cashman, and Kelly [40] have applied this model to study H-Darrieus VAWT. 
However, these models are first attempt designs and they need to be validated. Wind tunnel 
experiments are need to be conducted for their validation which is expensive considering both time 
and cost. So, another approach to study their aerodynamic behavior is to study using CFD.