PENGARUH TANDEM STAGGER CYLINDER TERHADAP PERFORMA HIDRODINAMIKA DRAG TURBIN

Turbin Savonius memiliki konstruksi sederhana dan kemampuan self-starting yang
baik, tetapi performanya masih terbatas akibat drag negatif pada returning blade serta
pembentukan wake yang menyebabkan kehilangan energi. Penelitian ini bertujuan
menganalisis pengaruh empat circular cylinder dalam konfigurasi tandem-stagger
terhadap performa hidrodinamika turbin Savonius menggunakan simulasi
Computational Fluid Dynamics dua dimensi. Simulasi dilakukan menggunakan
pendekatan Unsteady Reynolds-Averaged Navier–Stokes dan model turbulensi SST kω dengan fluida kerja air, kecepatan aliran bebas 1 m/s, bilangan Reynolds 3,6 × 10⁵,
serta sudut stagger 45°. Variasi spacing ratio yang digunakan adalah S/D = 0,8; 0,9;
1,0; dan 1,1. Model numerik diverifikasi melalui uji grid independence dan divalidasi
dengan membandingkan kecenderungan hasil simulasi terhadap penelitian
sebelumnya. Parameter yang dianalisis meliputi distribusi tekanan, pola aliran,
karakteristik wake, coefficient of moment, dan coefficient of power. Hasil penelitian
menunjukkan bahwa seluruh variasi cylinder mampu meningkatkan performa
dibandingkan turbin konvensional. Konfigurasi S/D = 0,9 menghasilkan performa
terbaik dengan Cm maksimum sebesar 0,515 dan Cp maksimum sebesar 0,373, yang
meningkat masing-masing sekitar 41,5% dan 62% dibandingkan turbin konvensional.
Konfigurasi tersebut mampu mengarahkan aliran menuju advancing blade,
mengurangi drag negatif pada returning blade, serta menghasilkan pola wake yang
lebih teratur. Dengan demikian, konfigurasi tandem-stagger cylinder efektif digunakan
sebagai metode passive flow control untuk meningkatkan performa hidrodinamika
turbin Savonius.
Kata kunci: turbin Savonius, tandem-stagger cylinder, hidrodinamika, CFD,coefficient of moment, coefficient of power.

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The Savonius turbine has a simple construction and good self-starting capability, but
its performance remains limited due to negative drag on the returning blade and wake
formation that causes energy losses. This study analyzes the effect of four circular
cylinders arranged in a tandem-stagger configuration on the hydrodynamic
performance of a Savonius turbine using two-dimensional Computational Fluid
Dynamics simulations. The simulations were performed using the Unsteady ReynoldsAveraged Navier–Stokes approach and the SST k-ω turbulence model, with water as
the working fluid, a free-stream velocity of 1 m/s, a Reynolds number of 3.6 × 10⁵, and
a stagger angle of 45°. The tested spacing ratios were S/D = 0.8, 0.9, 1.0, and 1.1. The
numerical model was verified through a grid-independence test and validated against
previous studies. The evaluated parameters included pressure distribution, flow
patterns, wake characteristics, coefficient of moment, and coefficient of power. The
results showed that all cylinder configurations improved turbine performance
compared with the conventional design. The S/D = 0.9 configuration produced the best
performance, with a maximum Cm of 0.515 and a maximum Cp of 0.373, representing
improvements of approximately 41.5% and 62%, respectively. Therefore, tandemstagger cylinders are effective passive flow-control devices for improving the torque
and power performance of a hydrokinetic Savonius turbine.
Keywords: Savonius turbine, tandem-stagger cylinder, hydrodynamics, CFD,
coefficient of moment, coefficient of power.