## 3 Results and Discussions
### Uniform Twist Control with Single-Harmonic Inputs
due to the compromised design of conventional rotors are the key factors limiting the rotor performance. For condition B, the rotor power reductions relative to the baseline rotor that are obtained with 1-3/rev harmonic inputs are 2.08%, 4.01% and 1.09%, respectively. The optimal amplitudes are 0.9\({}^{\circ}\)/m, 0.4\({}^{\circ}\)/m, and 0.2\({}^{\circ}\)/m. The optimal phase angles of the 1-3/rev harmonic inputs are 330\({}^{\circ}\), 225\({}^{\circ}\), and 90\({}^{\circ}\), as shown in Figure 12. The optimal schedules are shown in Figure 13. Generally, the increase in rotor power reduction begins  
Figure 11: Dimensionless rotor aerodynamic load distribution of the baseline rotor for condition B.  
to level off with the amplitude beyond 1.0\({}^{\circ}\)/m for the 1/rev uniform twist control, while the optimal amplitude for the 0/rev and 2-5/rev control is smaller. Therefore, the saturation limit of the amplitude for active control is set as 1.0\({}^{\circ}\)/m in the subsequent analysis and optimization work. Figure 14 shows the blade shaft moment increments of uniform twist control with 1-3/rev single-harmonic inputs relative to the baseline rotor for condition B. Figure 15 shows the distributions of dimensionless lift load increment (\(\Delta C_{Z}Ma^{2}\)) and drag load increment (\(\Delta C_{X}Ma^{2}\)) relative to the baseline rotor. The increase in angle of attack is the largest at the tip region of the blades due to the uniform twist control, which results in obvious variation of local loads. Figure 14: Blade shaft moment increments of uniform twist control with the 1-3/rev single-harmonic inputs relative to the baseline rotor for condition B.  
Figure 12: Rotor power reduction of uniform twist control with the 1-3/rev inputs for condition B.  
Figure 13: Optimal control schedules of uniform twist control with the 1-3/rev inputs for condition B. For the 1/rev control with the optimal phase angle of 330\({}^{\circ}\), the blades are actuated with pitch up deformations at the rear region on the advancing side and pitch down deformations at the front region on the retreating side. The 1/rev twist control induces loads shifting along the span. The loads on the blades shift towards the tip at the front region of rotor disk and the blade shaft moment decreases from approximately 40\({}^{\circ}\) to 250\({}^{\circ}\). Figure 15: Dimensionless load increment distributions relative to the baseline rotor using uniform twist control with the 1–3/rev single-harmonic inputs for condition B. The loads shift towards the tip at the rear region from approximately 250\({}^{\circ}\) to 40\({}^{\circ}\), which leads to a penalty in induced drag and increase the blade shaft moment. The negative twist rate is reduced on the advancing side. The angle of attack increases at the tip region and decreases at the root region. The drops of profile drag at the tip region and induced drag at the root region cause a significant decrease of the blade shaft moment at approximately 90\({}^{\circ}\). For the 2/rev control with the optimal phase angle of 225\({}^{\circ}\), pitch up deformations are generated at approximately 65\({}^{\circ}\) and 245\({}^{\circ}\), and pitch down deformations are generated at approximately 155\({}^{\circ}\) and 335\({}^{\circ}\). The negative-lift region on the advancing side decreases. The lift loads are alleviated at the front region on the advancing side and rear region on the retreating side. The induced drag loads and the blade shaft moment decreases from approximately 80\({}^{\circ}\) to 195\({}^{\circ}\) and from 285\({}^{\circ}\) to 30\({}^{\circ}\). The shifting of the lift loading zone towards the tip of the blades leads to the increase in blade shaft moment from approximately 30\({}^{\circ}\) to 80\({}^{\circ}\) and from approximately 195\({}^{\circ}\) to 285\({}^{\circ}\).