Circular Flow Disturbance Effect to Darrieus Tidal Current Turbine Performance in Kepa Strait

The Darrieus turbine is considered suitable for the ocean current characteristics of Indonesia, particularly in the Kepa Strait, East Nusa Tenggara. To enhance its performance and achieve optimal power output, this study proposes the integration of a circular foil-type flow disturbance positioned at an angle of attack of $-60^{\circ}$. Tidal current velocity data from the Kepa Strait were used as input for a numerical simulation conducted using Computational Fluid Dynamics (CFD). The study compares the power coefficient (Cp) of a conventional Darrieus turbine with that of turbines equipped with flow disturbances placed at distances of $1 / 4 \mathrm{D}$ and $1 / 2 \mathrm{D}$ from the turbine. The results show that the addition of a flow disturbance improves turbine performance, with closer placements yielding higher $\mathbf{C p}$ values. At a distance of $\mathbf{1} \boldsymbol{/} \mathbf{4 D}$, the flow disturbance increased Cp by up to 45.68 %, while at $1 / 2 \mathrm{D}$, the maximum improvement reached 33.46 %. These findings suggest that the proposed configuration can serve as a reference for designing high-performance Darrieus turbines for application in the Kepa Strait.