Helicopter noise footprint prediction in unsteady maneuvers

Abstract

This paper investigates different methodologies for the evaluation of the acoustic disturbance emitted by helicopter's main rotors during unsteady maneuvers. Nowadays, the simulation of noise emitted by helicopters is of great interest to designers, both for the assessment of the acoustic impact of helicopter flight on communities and for the identification of optimal-noise trajectories. Typically, the numerical predictions consist of the atmospheric propagation of a nearfield noise model, extracted from an appropriate database determined through steady-state flight simulations/measurements (quasi-steady approach). In this work, three techniques for maneuvering helicopter noise predictions are compared: one considers a fully unsteady solution process, whereas the others are based on quasi-steady approaches. These methods are based on a three-step solution procedure: first, the main rotor aeroelastic response is evaluated by a nonlinear beam-like rotor blade model coupled with a boundary element method for potential flow aerodynamics; then, the aeroacoustic near field is evaluated through the 1A Farassat formulation; finally, the noise is propagated to the ground by a ray tracing model. Only the main rotor component is examined, although tail rotor contribution might be included as well. The numerical investigation examines the differences among the noise predictions provided by the three techniques, focusing on the assessment of the reliability of the results obtained through the two quasisteady approaches as compared with those from the fully unsteady aeroacoustic solver.

Rotorcraft comprehensive code assessment for blade–vortex interaction conditions

“…The aerodynamic loads are determined by a solver developed at Roma Tre University based on a BEM approach for the solution of unsteady potential flows around lifting bodies, that is capable of dealing with bodies in arbitrary motion, in the presence of strong blade-vortex interactions (BVI). It has been extensively validated and successfully applied to aeroacoustic analyses of helicopter rotors (see, for instance, [22,23,24,25]).…”

Challenges and opportunities for low noise electric aircraft

“…226 To address the need for timely and specific low noise guidance, researchers have been developing several new approaches to managing aircraft noise. Taking advantage of increases in computing power and algorithms that use precomputed acoustic data, 227,228 it is possible to predict the noise radiation of rotorcraft in real time. 229 These techniques can be used to give pilots and operators real time feedback about the acoustic impacts of the operation.…”

2.3 - Developing a Novel Contactless Sensor for Helicopter Rotor State Measurements

“…In an effort to assess the capability to accurately predict the noise footprint of a maneuvering rotorcraft, in WP1 two variants of a quasi-steady computational approach have been compared to fully unsteady calculations in relation to typical and low-noise terminal trajectories [7,8]. The highly accurate, but inevitably burdensome, unsteady aeroacoustic solver, coupled with a sophisticated propagation model, has been used to correlate predictions with actual flight test data.…”