Numerical Investigation of Multi-Stage Hybrid Darrieus–Savonius Hydrokinetic Turbine Performance with Fibonacci Blades and Darrieus Solidity Variations

Dimas Rio Javani (Department of Mechanical Engineering, Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia)
Sutardi (Department of Mechanical Engineering, Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia)

RESWARA: Jurnal Riset Ilmu Teknik
Vol. 4 No. 3 (2026): RESWARA: Jurnal Riset Ilmu Teknik, July 2026

Indonesia’s increasing energy demand and fossil fuel crisis have accelerated the transition toward New and Renewable Energy (NRE). With an NRE potential of 3,600 GW and utilization still below 2%, hydrokinetic turbines offer a promising solution for harnessing water flow energy. This study numerically investigated the performance of a multi-stage hybrid Darrieus–Savonius hydrokinetic turbine using Computational Fluid Dynamics (CFD). The proposed design combined Fibonacci spiral-based Savonius blades with NACA 0018 Darrieus blades. Simulations were conducted within a Tip Speed Ratio (TSR) range of 0.2–2.3 and solidity ratios of 0.5–1.1 to determine the optimum turbine performance. The results showed that blade solidity significantly influenced energy extraction efficiency in a non-linear manner. The optimum condition was achieved at a solidity ratio of 0.95 and TSR = 1, producing a maximum power coefficient (Cp) of 0.082. Flow visualization indicated stable negative pressure regions and higher local flow acceleration, which reduced flow separation around the blades. In contrast, a solidity ratio of 1.1 at TSR 0.8 caused stronger blockage effects and wake interactions, increasing hydrodynamic drag and reducing turbine performance. These findings demonstrate that solidity ratios close to unity can improve torque stability and turbine efficiency under low TSR conditions.