This study shows the results of pressure distribution measurements on a rotor blade of a horizontal axis wind turbine under various yawed operations. The experiments are carried out in a wind tunnel with a $2.4m$ diameter test rotor. In the measurements, the power curve and pressure distributions are measured for different azimuth angles. By increasing yaw angle, the maximum value of power coefficient of the rotor decreases. The sign of the yaw angle does not have any effect on power performance. The aerodynamic forces are discussed using the axial and rotational force coefficients for each azimuth angle. In the case of higher tip speed ratios, the blade section passing on the upstream side in yawed operations has a greater contribution to the rotor torque than that on the downstream side. In this tip speed range, the aerodynamic forces at the 70% radius section appear proportional to the angle of attack. In the case of the lower tip speed ratios, the blade on the downstream side does not contribute to rotor torque, which appears to result from separation.

Leading-edge protuberances on airfoils or wings have been considered as a viable passive control method for flow separation. In this paper, the aerodynamic performance of a modified airfoil with a single leading-edge protuberance was investigated and compared with the baseline NACA 63₄-021 airfoil. Spalart–Allmaras turbulence model was applied for the numerical simulation. Compared to the sharp decline of baseline lift coefficient, the stall angle of the modified foil decreased and the decline of the lift coefficient became mild. The poststall performance of the modified airfoil was improved, while the prestall performance was declined. Asymmetric flows along the spanwise direction were observed on the modified airfoil, and the local region around one shoulder of the protuberance suffered from leading-edge separation at prestall angles of attack, which may be responsible for the performance decline. At poststall angles of attack, the attached flows along the peak of the protuberance with a sideward velocity component would help improving the total performance of the airfoil. Experimental visualization methods, including surface tuft and smoke flow, were performed, and the asymmetric flow pattern past the protuberance was successfully captured. This specific phenomenon may be largely related to the formation of the biperiodic condition and other complicated flow patterns induced by multiple leading-edge protuberances. The formation mechanism and suppression method of the symmetry breaking phenomenon should be investigated more deeply in the future to guide the practical application of this passive control method.

In recent years, leading-edge tubercles have gained significant attention as an innovative biomimetic flow control technique. This paper explores their impact on the aerodynamic performance and flow patterns of an airfoil through wind tunnel experiments, utilizing force measurements and tuft visualization at Reynolds numbers between 2.7 × 10⁵ and 6.3 × 10⁵. The baseline airfoil exhibits a hysteresis loop near the stall angle, with sharp changes in lift coefficient during variations in the angle of attack (AOA). In contrast, the airfoil with leading-edge tubercles demonstrates a smoother stall process and enhanced post-stall performance, though its pre-stall performance is slightly reduced. The study identifies four distinct flow regimes on the modified airfoil, corresponding to different segments of the lift coefficient curve. As the AOA increases, the flow transitions through stages of full attachment, trailing-edge separation, and local leading-edge separation across some or all valley sections. Additionally, the study suggests that normalizing aerodynamic performance based on the valley section chord length is more effective, supporting the idea that leading-edge tubercles function like a series of delta wings in front of a straight-leading-edge wing. These insights provide valuable guidance for the design of blades with leading-edge tubercles in applications such as wind and tidal turbines.

Surface-mobile platforms have explored the moon and the red planet for nearly half century, providing a wealth of scientific data. However, surface mobility on planetary bodies remains a challenging task. In this letter, the formulation of reaction force by a grouser with a generalized geometry for a wheel of a planetary rover is presented, along with its verification through comparisons with the results by the conventional geometry. In a simulation study, the resistive force theory is applied to a general grouser geometry model. The study determines the impact of several parameters, particularly the grouser inclination, on draw-bar pull. The results obtained from the study suggest the formulation of a design for the grouser that is nearly optimal in its capacity to maximize the draw-bar pull per sinkage. We also apply the proposed geometry to the wheel on LEV-1, demonstrating that it works well in actual lunar operations.

This paper presents the hopping performance evaluation on 3 types of terrains and novel foot pad designs for efficient traverse of hopping rovers. In order to continue the exploration of planetary environments without any human help, optimization and efficient designs of rovers are essential. In particular, improving the robustness and decreasing the energy consumption are crucial aspects of rovers design. Hopping efficiency on sandy surfaces is strikingly worse than on hard ground, because such soil is deformed and easily causes slip, and the dynamics are hard to estimate. In this paper, we discover the hopping performance on three kinds of terrains. Moreover, we also propose the method of increasing hopping performance on soft soil. Inspired by the conventional wheeled vehicle design, treads, called grouser, are installed on the bottom of the foot pad. While grousers are effective on hard ground and soft soil, they are ineffective on bilayer terrain. Bilayer means that hard ground is covered with thin regolith. And the other novel grouser shape is designed based on the soil interaction model using a multi-objective evolutionary algorithm. The proposed design improve the hopping performance on soft soil in comparison with the straight grouser.

The speed, accuracy, and adaptability of human movement depends on the brain performing an inverse kinematics transformation-that is, a transformation from visual to joint angle coordinates-based on learning from experience. In human motion control, it is important to learn a feedback controller for the hand position error in the human inverse kinematics solver. This paper proposes a novel model that uses disturbance noise and the feedback error signal to learn coordinate transformations of the human visual feedback controller. The proposed model redresses drawbacks in current models because it does not rely on complex signal switching, which does not seem neurophysiologically plausible. Numerical simulations show the effectiveness of the model.