Session: 41-02 Wind Turbine Computational Studies

Paper Number: 153798

Dynamic Analysis of Vertical Axis Wind Turbines Under Unsteady Wind Conditions Considering Inertial Effects 

Vertical Axis Wind Turbines are simple to design, capture wind from any direction, and perform well in turbulent conditions, but leveraging these advantages requires a clear understanding of their dynamics in real-world conditions, which this work sets out to do. Traditional research often analyses VAWTs at a constant or prescribed angular velocity, which does not reflect real-world conditions where wind speeds fluctuate. This paper addresses the research gap by analysing the dynamic interaction between the rotor and fluid under unsteady wind conditions, offering a more accurate representation of real-world performance. We specifically examine the rotor's response to three wind profiles: an increasing ramp (5–12 m/s), a decreasing ramp (5–12 m/s), and wind gusts with noise. To achieve this, the aerodynamic analysis is conducted using a quasi-static approach based on the results derived by the QBlade implementation of Double Multiple Streamtube Model, where power coefficient, torque coefficient, and rotor torque are obtained for the operational velocity range between 5 and 12 m/s, while the turbine’s structural and geometric properties are modelled using a CAD system to obtain precise evaluation of the rotor inertia. Finally, the dynamic simulation is implemented in a in-house MATLAB code using the equation of motion for the rotor-generator assembly. The generator torque is regulated such that it is equal to the torque corresponding to the angular velocity for which the power is maximum given a constant wind speed. This is how the dynamic behavior of VAWTs under unsteady wind conditions is analysed. Results of the simulation are obtained in terms of the variations of angular velocity and rotor torque with respect to time. The results are expected to demonstrate that rotor inertia significantly influences the dynamics of the rotor by smoothing out fluctuations in rotor speed caused by rapid changes in wind velocity. It is anticipated that the response of angular velocity will exhibit a delay when transitioning to steady state, particularly during sudden changes in wind speed, both for step increases and decreases. This delay is also expected during gusts, where inertia is likely to filter out noise-induced fluctuations, allowing the rotor to respond more gradually to variations in wind velocity. The differing behaviours of rotor torque during step increases and decreases in wind velocity are primarily anticipated to be influenced by inertia and torque imbalance. In a step increase, rotor torque is expected to gradually rise to a new steady state, with inertia moderating the response. In contrast, during a step decrease, generator torque may quickly exceed rotor torque, leading to rapid deceleration and potentially causing the rotor torque to drop to zero as the system seeks to regain equilibrium. Similar patterns are expected to emerge during wind gusts, where rotor torque may rise sharply when the wind speed increases followed by a decline as the wind speed decreases but, unlike the step decrease case, the rotor torque may not fall to zero due to a more gradual decrease in wind speed.

Presenting Author: Alessio Castorrini Sapienza University of Rome

Presenting Author Biography: Dr. Castorrini is Assistant Professor at Sapienza University of Rome. He is lecturer of fluid machinery, energy conversion systems, and fluid-structure interaction. His research activities concern the development and application of computational mechanics applied to fluid machinery and wind energy, mainly focusing on CFD and fluid-structure interaction.

Authors:

Sanshodhan Shende Sapienza University of Rome
Lorenzo Tieghi University of Trento
Alessandro Corsini Sapienza University of Rome
Alessio Castorrini Sapienza University of Rome