A Model For Rotor Broadband Noise Prediction PDF Download

The capability to predict aircraft noise is important in the development of acoustically aware aircraft. The first principles noise prediction model developed in this work evaluates medium weight-class aircraft models and a conceptual electric vertical takeoff and landing (eVTOL) design. This work contains four significant system improvements over the previous version of the noise prediction system: the incorporation of a dual compact thickness noise model, a standardized command file generation system for PSUHeloSim, an improved trim matrix solution for the HeloSim model, and the capability to "calibrate" broadband noise predictions. These enhancements, along with the definition of new helicopter models developed in this work will be described. Multiple helicopters were used to validate the noise prediction system. The Sikorsky S-76D and Bell 205 from Phase III of a joint NASA/FAA/ARMY flight test were simulated together with the Bell 407 and Bell 206 models from Phase II test by the same participants. The simulated noise from medium-weight class aircraft, such as the S-76D and Bell 205 was compared with the noise predictions for the lighter weight class aircraft, i.e., the Bell 407 and Bell 206. In particular, the S-76D was compared against the Bell 407 because both aircraft have four-bladed main rotors. The Bell 205 was compared with the Bell 206 because both aircraft have two-bladed main rotors. It was determined that the directionality of the thickness and broadband noise was similar between aircraft of different weight-classes. Loading noise magnitude and directivity changed between light and medium weight-class aircraft. A novel eVTOL concept based on the proposed Jaunt Journey aircraft was modeled in the noise prediction system for multiple steady-flight conditions. Comparisons were made with a baseline propeller to evaluate the effectiveness of a low-noise electric propeller design. The novel eVTOL rotor indicated low thickness and loading noise and significant reduction in broadband noise. A full model of the eVTOL aircraft was used to determine the noise of each of the propellers, main rotor, and full aircraft. The predicted noise of the novel eVTOL indicated lower total noise than a comparable conventional aircraft design.