Evaluation of the Swirl Characteristics of a Tidal Stream Turbine Wake

Morris, C. E., Mason-Jones, A., O'Doherty, D. M., Tatum, S. C., O'Doherty, T. O., & Thompson, D. (2013). Evaluation of the Swirl Characteristics of a Tidal Stream Turbine Wake. EWTEC 2013 – 10th European Wave and Tidal Energy Conference. Aalborg, Denmark.

Abstract

Tidal stream turbines (TSTs) produce a rotating downstream wake. This paper describes the characteristics of the swirl flow in the wake of a TST with a view of comparing these against classical swirl theory. Using computational fluid dynamics the paper shows the non dimensional swirl number for a 2, 3 and 4 bladed TST. The characteristics of velocities, pressure drop, viscosity are described for the 3 bladed TST. To ensure the validity of the data sets the characteristics are compared to the findings in the literature for a set of generic swirl generators. The swirl number for the TSTs in a 3.08 m/s tidal (uniform) flow was found to range between 0.168 and 0.263, which describes weak swirl flow. Whilst the characteristics are in agreement with theory it also means that the swirl component of the wake is not coupled with the axial component at the lower