Figure 3. A 2-D view of the four turbines having varying phase shift angles, where the green blades are for the lower rotor while the black blades are for the upper rotor.

From

CFD Investigation of the Effect of Multiple Phase Shift Angles on the Performance of a Two-Stage Savonius Wind Turbine

Susan Kariuki, Churchill Saoke, Joseph Kamau, Patrick Muiruri

American Journal of Energy Research. 2024, 12(3), 63-69 doi:10.12691/ajer-12-3-3