Influence of Tip Speed Ratio on Wake Flow Characteristics Utilizing Fully Resolved CFD Methodology

Dominant flow structures in the wake region behind the turbine employed in the
Blind Test campaign [1], [2] is investigated numerically. The effect on the wake configuration at
variable operating conditions are studied. The importance of the introduction of turbine tower
inside the numerical framework is highlighted. High-fidelity simulations are performed with
Multiple Reference Frame (MRF) numerical methodology. A thorough comparison among the
cases is presented, and the wake evolution is analyzed at variable stations downstream of the
turbine. Streamlines of flow field traveled towards ground adjacent to turbine tower and strongly
dependent on the operating tip speed ratio. Wake is composed of tower shadow superimposed
by rotor wake. Shadow of the tower varies from x/R=2 until x/R=4 and breaks down into small
vortices with the interaction of rotor wake. This study also shows that the wake distribution
consists of two zones; inner zone composed of disturbances generated by blade root, nacelle and
the tower, and an outer zone consisting of tip vortices.