Start-up dynamics of vertical axis turbines

We present an experimental study of the self-starting behavior of vertical axis turbines, in order to guide the design of systems that operate in unsteady flows. The torque, angular velocity, and power generation of a scale model turbine were measured in a free surface water tunnel for different starting angles of the rotor blades and for different flow speeds. The starting behavior of the turbine was found to be sensitively dependent on the initial angle of the rotor at low flow speeds. A conceptual model was developed in order to explain the observed behavior in terms of the instantaneous lift and drag on the rotor blades.