Transient CFD analysis of a floating pico-hydro turbine under fully turbulent river flow conditions in South Sumatra

This study investigates the transient hydrodynamic performance of a floating pico-hydro turbine under fully turbulent river flow using a two-phase transient Reynolds-Averaged Navier-Stokes (RANS) approach with the SST k–ω turbulence model. Simulations were conducted at inlet velocities of 1.0, 1.2, and 1.4 m/s, corresponding to Reynolds numbers ranging from 5 × 10⁵ to 7 × 10⁵. The analysis focuses on torque development, wake behavior, and mechanical power across varying flow rates. Torque stability is quantified using the coefficient of variation (CoV) to assess unsteady loading. Results indicate that torque increases nonlinearly with velocity, while torque fluctuation rises from 3.2% to 5.6% as vortex shedding intensifies. The maximum predicted mechanical power is 58.6 W at 1.4 m/s. Mechanical power does not scale precisely with the cube of velocity, indicating increased hydrodynamic losses at higher Reynolds numbers. These findings provide a numerical reference for future experimental validation and contribute to a deeper understanding of the performance of floating pico-hydro turbines in riverine environments.