Vertical Axis Wind Turbine (VAWT)

Vertical Axis Wind Turbine (VAWT) CFD Simulation by Mesh Motion Method, ANSYS Fluent Training

Description

This project simulates airflow around a Vertical Axis Wind Turbine (VAWT) using ANSYS Fluent. VAWTs are a class of wind turbine in which the rotor shaft is oriented vertically (perpendicular to the ground) rather than horizontally, allowing them to capture wind from any direction without needing to actively orient, or "yaw," toward the wind — a key advantage over horizontal axis turbines in turbulent or variable-direction wind environments such as urban settings.

In this simulation, the turbine's three blades rotate at 2.8285 rad/s while incoming air approaches at 7 m/s, capturing how the surrounding air responds to the moving blades and revealing the associated flow parameters. A particularly important phenomenon in VAWT aerodynamics also emerges in this simulation: dynamic stall, which occurs because each blade's angle of attack relative to the oncoming flow changes continuously as it rotates around the vertical axis — unlike a horizontal axis turbine, where blade angle of attack relative to the wind stays comparatively steady. This continuously varying angle of attack can drive the flow into and out of stall multiple times per rotation, generating unsteady lift and torque fluctuations that significantly affect both turbine performance and structural loading.

The 3D geometry was designed in Design Modeler and meshed in ANSYS Meshing using a hybrid mesh combining structured and unstructured regions, totaling 904,145 elements.

Methodology

The Mesh Motion method was used to model the turbine's rotational movement, physically rotating the mesh to track the blades' motion through the domain rather than relying on a rotating reference frame. The simulation was run as unsteady (transient), which is essential for capturing the time-varying dynamic stall behavior described above, with turbulence modeled using the standard k-epsilon model.

Conclusion

Since the primary objective was to investigate airflow behavior around the VAWT, the resulting 2D contours of pressure, velocity, and turbulent intensity provide a detailed picture of this interaction. The pressure contour shows a critical rise in air pressure directly ahead of the blade zone, corresponding to the region where each blade first meets the oncoming flow, while the velocity contour reveals wake structures forming and trailing behind the rotating blades.

Together, these results characterize how the turbine's continuous rotation reshapes the surrounding flow field throughout each cycle, offering insight into the unsteady aerodynamic loading and dynamic stall behavior that distinguishes VAWT performance from that of horizontal axis designs.