Comparative evaluation of DMST and LLFVW models for predicting the aerodynamic performance of vertical axis wind turbines

Vertical axis wind turbines (VAWTs) require efficient aerodynamic models that can predict their performance at a low computational cost, especially in the preliminary stages of design and parametric analysis. This paper presents a comparative evaluation of two widely used simplified aerodynamic models: the Double Multiple Stream Tube (DMST) model and the Lift Line with Free Vortex Trail (LLFVW) model. Both approaches are applied to a small-scale Darrieus-H turbine and validated using experimental data reported in the literature. Two modeling configurations with different levels of physical complexity are analyzed, considering the influence of induction losses, wake expansion, and unsteady aerodynamic effects. The results show that the DMST model tends to overestimate the maximum power coefficient and shift the optimum operating point toward higher tip speed ratio (TSR) values, even when corrections for tip losses and variable induction factors are incorporated. In contrast, the LLFVW model more accurately reproduces wake dynamics and non-stationary effects, achieving better agreement with experimental data across the entire operating range. In particular, the LLFVW more accurately captures both the magnitude and position of peak performance, identifying itself as a more reliable model for the aerodynamic prediction of VAWTs.