The focus of the present study is to examine the performance of the conventional and modified Savonius turbine with and without deflectors. First, the performance of the conventional Savonius rotor and a modified Savonius rotor, which originally proposed by Bach [7], were examined through both experiments and numerical simulations. The numerical study, which employed the computational fluid dynamics
software, STAR-CD, aimed to provide detailed analysis of the factor affecting rotor's performance with both 2-D and 3-D simulations. The numerical results of the convention Savonius rotor were also compared with the experimental study presented by Blackwell et al. [2], with favorable results. Both experiments and simulations have shown better performance of the modified Savonius rotor with the improvement of efficiency being about 3% to 5 %. Second, the deflector configurations, which reported by Altan et al. [10] and Kailash et al. [12], were added around the conventional Savonius rotor in numerical simulations to examine their effects on the rotor's performance. With the addition of the deflectors, it has been revealed that the maximum power output from the rotors can significantly increase by 40%.

1 Introduction
1.1 Introduction
1.2 Literature Review
1.3 Motivations and Objectives
2 Experimental Methods
2.1 Rotors Involved
2.2 Power and Efficiency Calculation
2.3 Experimental Set-up and Procedures
3 Numerical Methods
3.1 Rotors and Deflector Configurations
3.2 Simulation Domains and Boundary Conditions
3.3 Torque Computation for the Simulations
3.4 Introduction to the STAR-CD
3.5 Governing Equations
3.5.1 The Continuity and Momentum Equations
3.5.2 RNG k-epsilon Model
3.5.3 Standard Wall Function
3.6 Discretization
3.7 Pressure Implicit with Splitting of Operator (PISO) Algorithm
3.7.1 Equations
3.7.2 Solution Sequence
3.8 Sliding Mesh
3.9 The Grid-Independent Tests
4 Results and Discussion
4.1 Performance Comparison between the Rotors
4.1.1 Experimental Results
4.1.2 Simulations in the Wind Tunnel
4.2 The Effect of Deflectors on Performance
5 Conclusion

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