Mechanically guided assembly techniques yield complex 3D microvascular networks with multifunctional characteristics.

In recent years, with the development of intelligent technology, rotorcrafts have been widely used in unmanned collaborative missions due to their excellent maneuverability and vertical flight capability. However, the flight process of rotorcrafts generates a noticeable induced flow that affects the flight safety of surrounding aircrafts. In the current research on the aerodynamic interference of multiple rotorcrafts, scholars are focusing on the effects of the upper rotor on lower rotors, while ignoring the induced influence of lower rotors. In this research, the detached eddy simulation was used to analyze the numerical and flow characteristics of an upper small-ducted-rotor (SDR) disturbed by a large-rotor (LR). The Q-criterion and power spectrum density method were employed to analyze the wake vortex evolution characteristics of the SDR. The results indicate that the thrust loss of the duct is significantly positively correlated with the rotational speeds of both SDR and LR, whereas the thrust loss of the rotor is only associated with the rotational speed of LR. The thrust loss of the duct is significantly greater than that of the rotor, primarily due to the disruption of attachment vortices and the generation of new shear-layer shedding vortices. Wake analysis reveals that the disturbance from LR simultaneously enhances both the kinetic and turbulent kinetic energy around SD, resulting in the discovery of multiple energy peak frequencies in the near- and mid-field distinct from the blade-passing frequency. This research helps analyze rotorcrafts' flight safety during the collaborative processes.

By combining the flapping and rotary motion, a flapping wing rotor (FWR) shows unique kinematics of motion. It can produce a significantly higher aerodynamic efficiency and lift coefficient than insect-like flapping wings. However, due to the lack of controllable FWR aerial vehicles, the effect of different flapping parameters of the FWR on aerodynamic characteristics and efficiency remains to be evaluated experimentally. In this work, we conduct experimental studies to investigate the FWR’s lift performance based on our previous vehicle design, which has demonstrated sustained stable hover and maneuver. In particular, by using such flyable FWR as the test platform, the changes in attack angle of the wing, the torsion of wings, different neutral positions, different up and down flapping angles, and different flapping amplitudes, were studied respectively. CFD simulation was used as an auxiliary and supplementary means for validation. As a result, design essentials to lift maximization of the FWR are proposed. The result proves that changing the attack angle and the torsion of the wing will have a certain impact on the lift. In addition, the ideal lift force can be generated when the neutral position tend to zero degrees and the up and down flapping angles tend to be equal. With the growth of the flapping amplitude, the lift force increases continuously. These experimental results provide important design cues for maximizing lift and payload capability of FWR-MAVs.

A static aeroelastic analysis of the flexible trailing edge is conducted to calculate the deformed shape, aerodynamic coefficients and corresponding driving pressure. A physical flexible trailing edge model is manufactured using a honeycomb structure, which is measured based on binocular vision. The quadratic response surface method is adopted to establish the pneumatic artificial muscle actuator model. The wire-pulley transmission model is built to identify the existence of equivalent forces and produce the equivalent forces as the substitute of actuation force. A finite element model of the flexible trailing edge is established, which is validated by the test data. A nonlinear relationship is found between the driving pressure and deflection angle. The pressure needed to bear the structural stiffness is found to be much larger than that of the aerodynamic load. With the increase in pressure, the magnitude of the lift coefficient increases less. However, the magnitude of the drag coefficient increases more with the increase in pressure under 0.2 MPa. When the driving pressure exceeds 0.2 MPa, the relationship between them is nearly linear.