Aerodynamic and Aeroacoustic Analysis of Installed Pusher-Propeller Aircraft Configurations

Abstract

In this paper, the aeroacoustic phenomena characteristic of a pusher-propeller configuration and their aerodynamic causes are discussed and analyzed. The work was done in the framework of the European-funded project CESAR (for 'cost effective small aircraft'). The configuration under study is based on an industrially relevant business aircraft design with a wing-mounted pusher propeller, which features a close coupling of the turboshaftengine exhaust nozzles and a five bladed propeller. An established numerical analysis approach is applied in this study, which couples a high-fidelity unsteady aerodynamic simulation using the DLR unstructured finite volume flow solver (TAU) code with the DLR Ffowcs-Williams-Hawkings code APSIM for a subsequent aeroacoustic evaluation. A detailed analysis of the contributions of various components of the installation as well as flight-condition specific parameters toward the overall noise generation by the propeller is presented, which highlights the dominant role the engine-jet impingement on the propeller plays for the aeroacoustic characteristics of this type of aircraft configuration. A detailed analysis of specific aspects of the input surface used for the aeroacoustic analysis is made through a comparison between the results achieved using both impermeable and permeable Ffowcs-Williams-Hawkings formulations. The numerical error due to both jet exhaust and propeller wake impingement on the Ffowcs-Williams-Hawkings permeable surface as well as the impact of cutting a hole in this permeable surface to avoid possible issues of these effects are discussed. Nomenclature BPF= blade-passing frequency, Hz C D;L = drag and lift coefficient C T = thrust force coefficient p = pressure, N=m 2 R = propeller radius, m T = period length, s t = time, s u, v, w = velocity components in the Cartesian coordinate system, m=s = angle of attack, deg = density, kg=m 3 = azimuth angle, deg

Propeller installation effects on turboprop aircraft acoustics

“…Calculations with a time-domain linearized version of the FWH equation [36] including non-uniform propeller inflow and time-varying blade loads [34]. acoustically better installation solutions, as for example in [41] or in the German BNF project [42,43] for a tractor configuration and in the European CESAR project [44,45] for a pusher configuration.…”

The numerical CFD investigation of hub losses of pushing air propellers with tandem joined blades of small sized unmanned aerial vehicles

“…The air flow in the root part of the propeller is subjected to complex physical influences, leading to the formation of a hub vortex [7,8], which significantly affects the characteristics of the propeller. This effect can be more or less intense.…”