Cfd modelling of h-darrieus vertical axis wind turbine

2.1 ANALYTICAL STUDY APPROACH OF H-DARRIEUS VAWT 
Starting from simple 1D equations Multiple Stream Tube Model or Vortex Method, researchers 
have continued their work to present day to capture the real characteristics of the complicated 
turbulence flow.
2.1.1 Momentum Model 
2.1.1.1 Single Streamtube Model 
Templin [24] proposed the single streamtube model and this model was used during the first attempt 
to study VAWT using momentum theory. This model can be used to estimate the lightly loaded 
wind turbine’s overall performance. However, this overestimates the power than that of the 
experimental values. Variation of velocity of wind across the rotor is also not considered. [25] 
2.1.1.2 Multiple Streamtube Model 
This model is a more developed version of the Single Streamtube model developed by Wilson and 
P.B.S. [26] where the rotor is divided into a number of streamtubes. These streamtubes are 
independent and parallel. Then the blade element theories and the momentum theories are applied at 
each of these tubes. This model was then further developed by James H Strickland [27], Muraca, 
Stephens, and Dagenhart [28], Sharpe [29], Read and Sharpe [30]. Tai et al. [31] and Roh and Kang
[32] have applied this model on H-Darrieus turbine and studied the performance. 
2.1.1.3 Double-multiple Streamtube model 
Paraschivoiu [33] has worked on the double-multiple stream tube (DMST) method for Darrieus type 
VAWT modelling. From their study, they have found that the double-multiple stream tube method 
includes dynamic stall and secondary effects that can be useful in structural design of Darrieus 
rotors.
Beri and Yao [34] have worked on the modelling of unsteady flow analysis of VAWT. Here also 
they used the double-multiple stream tube (DMST) method for the performance prediction of fixed 
pitched three blade VAWT with NACA 0018 blade profile. They also analyzed 2D unsteady flow 
with modified at the trailing edge using CFD. The comparing the power coefficient obtained from 
both DMST and CFD, it was observed that DMST showed negative torque generated at low tip 

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speed where CFD results showed positive torque. The maximum power coefficients of the two 
models also came at a normal range. 
Paraschivoiu, Saeed, and Desobry [35] summarizes the progress made in the development of the 
different numerical tools for the simulation of the flow field around the VAWT as well as the 
dynamic-stall phenomenon of VAWT blades. The paper highlights the current capabilities and 
limitations of aerodynamic models with emphasis on double multiple stream tube (DMST) model as 
a design tool. This study concludes that further work is under consideration to develop improved 
models of the wind encountered by the rotor, the atmospheric flow across a site, the wake that 
affects blades in addition to the development of optimization tools.