Analytical wake model for coaxial dual-rotor turbines

This work develops and validates a novel analytical wake model for coaxial dual-rotor turbines. With the diameters, and axial induction factors of the upstream and downstream rotors, and the freestream velocity, the proposed model estimates the wake velocity deficit in the near- and far-wake of the coaxial turbine. It is developed by utilizing the Bernoulli principle along the streamlines that pass through the near- and far-wake control volumes and the conservation laws for mass and momentum. This simple model can be used to calculate the velocity distribution in the wake using just one parameter. The wake prediction is contrasted with CFD results for various flow conditions to find good agreements between them. The novel wake model can be useful for solving the turbine farm layout optimization problem that involve dual-rotor configurations for the power generators.