Savonius wind turbines are drag-based machines. As air flows over the blades, the drag force components on one side of the turbine are higher than on the opposite side, producing a torque. As the turbine rotates, this torque fluctuates, but remains positive. Savonius turbines do not require an external power source to start turning, and thus are very convenient for small to medium-sized power generators, for example on buildings and boats. They are also mechanically simple and typically easy to design for high wind speeds, for example when used in remote or high altitude locations.

Shown below is a Kumair vertical axis (VAWT) savonius wind turbine design. CFD analyses provided air loads, allowing optimization of the power generation. Click the pictures to see larger images. The image on the left shows streamlines, while on the right velocity magnitude contours are plotted on a plane perpendicular to the axis of the rotation.