Development of Bio-Inspired Low-Noise Propeller for a Drone

Abstract

Multicopter-type unmanned aerial vehicles, called drones, have been attracting wide attention because of their immense potential for use in various missions such as surveillance, reconnaissance, and delivery service. For the application of drones, however, their noise will be a serious issue especially when operating in urban areas, and to our knowledge, it has not been resolved yet. In this study, inspired by the unique wing structures of insects and birds, we have developed new low-noise-type propellers for drones. The various bio-inspired attachments of drones such as the serrations at the leading edge, velvet-like surface, and fringes at the trailing edge were tested, and their acoustic and aerodynamic performances were evaluated experimentally and numerically. Our results indicate that an attachment at the trailing edge can suppress the noise level while maintaining the aerodynamic efficiency of the proposed propeller close to that of the basic propeller.

Effect of Ducted Multi-Propeller Configuration on Aerodynamic Performance in Quadrotor Drone

“…To determine a high-performance duct design in the ducted single-propeller model in terms of the duct's cross-section and tip clearance, six parameters in toto are utilized, including the tip clearance (d e ) expressing the gap between propeller tip and duct inwall; the propeller height (h p ), i.e., the height difference between the center of the inlet ellipse (point D) and the center of the propeller bottom (point P); the diffuser angle (α) denoting the inclination angle of the diffuser; the diffuser length (l e ); the height of ellipse inlet (h e ); and the radius of the ellipse inlet (r e ), with an original value of d e = 0.001 m, h p = 0, α = 0, l e = 0.06 m (0.5R), h e = 0.06 m (0.5R), and r e = 0.02 m (0.167R) (Figure 3). The thickness of the duct model is fixed to be 0.0015 m. The 3D single-propeller model is based on DJI phantom 3 advanced (Figure 1a) as used in our previous studies [19,33]. A systematic CFD-based analysis was conducted to examine the high-performance duct model in terms of aerodynamic performance and duct volume.…”

“…CFD-based simulations were conducted with the commercial software ANSYS CFX 14.5 (ANSYS Inc) under the conditions of a rotational speed of 5400 rpm for all propeller models with/without ducts, which is identical to that utilized in our previous studies [19,33]. The Reynolds number (Re) of a single propeller is calculated to be 7.4 × 10 4 [19], and the RANS modelling of turbulent flow with the SST turbulence model was adopted with a 'high-resolution mode' for all the simulations of ducted single-propeller and ducted multi-propeller models [19,33,34].…”

“…CFD-based simulations were conducted with the commercial software ANSYS CFX 14.5 (ANSYS Inc) under the conditions of a rotational speed of 5400 rpm for all propeller models with/without ducts, which is identical to that utilized in our previous studies [19,33]. The Reynolds number (Re) of a single propeller is calculated to be 7.4 × 10 4 [19], and the RANS modelling of turbulent flow with the SST turbulence model was adopted with a 'high-resolution mode' for all the simulations of ducted single-propeller and ducted multi-propeller models [19,33,34]. Following our previous studies [19,33,34], we generated the inflation layer meshes with seven layers surrounding the propeller surfaces to ensure high resolution of the boundary layer adjacent to walls while being clustered at the wingtip, leading edge, and trailing edge.…”

“…The Reynolds number (Re) of a single propeller is calculated to be 7.4 × 10 4 [19], and the RANS modelling of turbulent flow with the SST turbulence model was adopted with a 'high-resolution mode' for all the simulations of ducted single-propeller and ducted multi-propeller models [19,33,34]. Following our previous studies [19,33,34], we generated the inflation layer meshes with seven layers surrounding the propeller surfaces to ensure high resolution of the boundary layer adjacent to walls while being clustered at the wingtip, leading edge, and trailing edge. Approximately 26 million and 48 million meshes (see in Sections 3.1 and 3.2) were successively generated for the ducted single-propeller and ducted multi-propeller, respectively.…”

“…A "Frozen Rotor (FR)" approach was utilized at the interface between inner rotating and outer stationary regions of both ducted singlepropeller and multi-propeller models to give the rotor an appointed constant rotating speed for the sake of 'freezing' the relative movements between the two frames, which thus ensures convergence to a stable state. Besides, a 'General Connection with No Frame Change/Mixing' model was employed at the interface between intermediate stationary FM efficiency [19,33] is adopted to evaluate the aerodynamic performance of the ducted single-propeller model and defined as:…”