Darrieus Wind Turbine

Darrieus Wind Turbine Evaluation — ANSYS Fluent CFD Simulation

Description

This project presents a CFD simulation of a Darrieus wind turbine using ANSYS Fluent. The vertical axis wind turbine (VAWT) is becoming ever more important in wind power generation thanks to its adaptability for domestic installations; however, VAWTs are known to have lower efficiency, especially compared to horizontal axis wind turbines (HAWTs). To improve their performance, industries and researchers work to optimize the rotor design, and CFD is employed here to evaluate this type of turbine. The project simulates the airflow near a vertical axis Darrieus turbine, investigating the airflow behavior and pressure distribution and studying the drag force.

Methodology

The geometry is drawn in Design Modeler and includes a rotary zone for the turbine walls and a stationary zone for the rest of the domain. The model is meshed in ANSYS Meshing with an unstructured grid of 2,289,621 cells. In this simulation, the rotational motion of the turbine blades must be defined — but rather than applying rotation to the blades themselves, the rotation is applied to the field around them, which requires separating a distinct moving zone from the overall computational domain. Because a vertical axis turbine's flow is time-dependent, as the position of the blades varies over time, the Mesh Motion method is used in the cell zone conditions, with the rotation axis and rotation speed defined. The inlet wind enters at 1 m/s, and the turbine zone rotates at 120 RPM. The simulation is carried out as an unsteady (transient) analysis.

Analysis

After the simulation, contours of velocity and pressure are obtained, along with velocity vectors around the turbine blades. The results show that the wind flow around the blades has a rotational movement, and the velocity field adjacent to the turbine wall has the highest gradient. The leading edge of the turbine wall experiences the highest pressure gradient, which is logical since the velocity there has just reached zero, and the streamline vectors illustrate the quality of the flow resolved in the wake — the core challenge of aerodynamic simulation. Finally, the drag force is 0.1826 N, which is accurate for a turbine with the noted specifications. By the end of this project, you'll be able to set up a transient Mesh Motion simulation of a vertical axis Darrieus wind turbine, define a rotating zone around the blades with the correct axis and speed, and interpret the velocity, pressure, and drag results that characterize VAWT aerodynamics.