<![CDATA[Abstract: The s-shaped turbine is a hydrokinetic turbine that has the potential to be applied to open channel flows due to its ability to operate at low flow velocities and its simple construction. However, the performance of this turbine is greatly influenced by the surrounding hydrodynamic conditions, including the geometry of the flow domain. This study aims to analyze the effect of variations in the open channel domain angle on the flow characteristics and performance of the s-shaped Savonius turbine using a Computational Fluid Dynamics (CFD) approach. Simulations were carried out at three variations of domain angles, namely 20°, 30°, and 40°, with an inlet flow velocity of 0.5 m/s, a turbine diameter of 76 mm, and a turbine height of 76 mm. The performance parameters analyzed included torque, power coefficient (Cp), and torque coefficient (Ct), as well as flow characteristics in the form of velocity contours, pressure contours, and streamlines. The simulation results show that variations in the domain angle have a significant effect on the flow distribution, pressure pattern, and torque stability produced by the turbine. The domain with an angle of 20° produces the highest Cp and Ct values, while the 30° domain shows a significant decrease in performance due to the increase in the recirculation zone and pressure imbalance around the rotor. Keyword: S-Shape Turbine; Hydrokinetics; Open Channel; CFD; Domain Angle Abstrak: Turbin tipe s-shape merupakan salah satu turbin hidrokinetik yang potensial untuk diaplikasikan pada aliran saluran terbuka karena kemampuannya beroperasi pada kecepatan aliran rendah dan konstruksinya yang sederhana. Namun, kinerja turbin ini sangat dipengaruhi oleh kondisi hidrodinamika di sekitarnya, termasuk geometri domain aliran. Penelitian ini bertujuan untuk menganalisis pengaruh variasi sudut domain saluran terbuka terhadap karakteristik aliran dan performa turbin s-shape menggunakan pendekatan Computational Fluid Dynamics (CFD). Simulasi dilakukan pada tiga variasi sudut domain, yaitu 20°, 30°, dan 40°, dengan kecepatan aliran masuk 0,5 m/s, diameter turbin 76 mm, dan tinggi turbin 76 mm. Parameter kinerja yang dianalisis meliputi torsi, koefisien daya (Cp), dan koefisien torsi (Ct), serta karakteristik aliran berupa kontur kecepatan, kontur tekanan, dan streamline. Hasil simulasi menunjukkan bahwa variasi sudut domain memberikan pengaruh signifikan terhadap distribusi aliran, pola tekanan, dan stabilitas torsi yang dihasilkan turbin. Domain dengan sudut 20° menghasilkan nilai Cp dan Ct tertinggi, sedangkan domain 30° menunjukkan penurunan kinerja yang cukup signifikan akibat meningkatnya zona resirkulasi dan ketidakseimbangan tekanan di sekitar rotor. Kata kunci: Turbin S-Shape; Hidrokinetik; Saluran Terbuka; CFD; Sudut Domain]]>
