Contra-Rotating Turbine

Contra-Rotating Turbine, ANSYS Fluent CFD Simulation Training

Description

This project simulates a contra-rotating VAWT turbine using ANSYS Fluent. A contra-rotating turbine is an axial flow turbine featuring two rows of blades that rotate at equal speed but in opposite directions. This configuration allows the turbine to recover energy and power that would otherwise be lost as airflow passes through the front row of blades — in effect, using two counter-rotating blade rows in this way doubles the turbine's overall torque output compared to a single-row design.

In this simulation, the Mesh Motion method defines the rotational behavior of the surrounding air. Two rows of three blades each were modeled, with a distinct airflow zone defined around each row, and mesh motion applied independently to both. Both rows rotate at 14.7 rad/s, but with their central rotation axes oriented in opposite directions — air around the upper blade row rotates clockwise, while the lower row rotates counterclockwise. Incoming airflow enters the computational domain at 5.3 m/s.

Geometry & Mesh

The 3D geometry was designed in Design Modeler, consisting of a rectangular cube-shaped computational domain containing the two parallel blade rows positioned in the middle, each with three blades. The domain was meshed in ANSYS Meshing using an unstructured grid totaling 3,747,546 cells.

Methodology

This steady-state simulation uses a pressure-based solver, with gravitational effects excluded. Turbulence was resolved using the standard k-epsilon model with standard wall functions for near-wall treatment. Boundary conditions included a velocity inlet at 5.3 m/s, stationary walls for both the upper and lower blade rows, a pressure outlet at 0 Pa gauge pressure, and symmetry boundaries elsewhere in the domain. The solution used SIMPLE pressure-velocity coupling with standard initialization.

Conclusion

Results include streamlines and 2D contours of velocity, pressure, and their respective gradients throughout the domain. The contours reveal that both pressure and velocity increase in the space between the two blade rows, correspondingly enhancing the torque and power generated at the turbine blades.

Specifically, the torque applied to the upper (clockwise-rotating) blade row measured 1.89 N·m, while the lower (counterclockwise-rotating) row measured 1.93 N·m — confirming that this contra-rotating configuration distributes approximately equal torque across both blade rows, validating the design's intended balanced energy recovery between the two counter-rotating stages.