A Computational Study on the Aeroacoustics of a Multi-Rotor Unmanned Aerial System

Abstract

The noise generated by a quadrotor biplane unmanned aerial system (UAS) is studied computationally for various conditions in terms of the UAS pitch angle, propellers rotating velocity (RPM), and the UAS speed to understand the physics involved in its aeroacoustics and structure-borne noise. The k-ω SST turbulence model and Ffowcs Williams-Hawkings equations are used to solve the flow and acoustics fields, respectively. The sound pressure level is measured using a circular array of microphones positioned around the UAS, as well as at specific locations on its structure. The local flow is studied to detect the noise sources and evaluate the pressure fluctuation on the UAS surface. This study found that the UAS noise increases with pitch angle and the propellers’ rotating velocity, but it shows an irregular trend with the vehicle speed. The major source of the UAS noise is from its propellers and their interactions with each other at small pitch angle. The propeller and CRC-3 structure interaction contributes to the noise at large pitch angle. The results also showed that the propellers and structure of the UAS impose unsteadiness on each other through a two-way mechanism, resulting in structure-born noises which depend on the propeller RPM, velocity and pitch angle.

Validating Confined Flame Noise Simulation Using External Sensor

“…The library has been used to simulate compressible free jets, and the results have been compared favorably to the experimental data using the FWH method [ 29 , 30 ]. It has also been used to simulate the marine propeller noise [ 31 ] and the rotor noise from unmanned arial vehicles [ 32 , 33 ]. Airfoil-generated noise and jet noise has been successfully simulated utilizing the libAcoustics implementation of the FWH method.…”

Noise Impact Assessment of UAS Operation in Urbanised Areas: Field Measurements and a Simulation

“…We can include a computational study on the aeroacoustics of a multirotor unmanned aerial system by Heydari, Sadat, and Singh [10], and a combined experimental and numerical assessment of UAV noise emissions by Cussen, Garruccio and Kennedy [11] among the latest works that prove the relevance of the issue. Several works are also devoted, for instance, to noise certifications, such as [12], or preliminary research on transverse noise topics [13][14][15][16][17][18][19][20][21].…”