As propeller-driven aircraft are the best choice for short/middle-haul flights, but their acoustic emissions may require improvements to comply with future noise certification standards, this work aims to numerically evaluate the acoustics of different modern propeller designs. Overall sound pressure level and noise spectra of various blade geometries and hub configurations are compared on a surface representing the exterior fuselage of a typical large turboprop aircraft. Interior cabin noise is also evaluated using the transfer function of a Fokker 50 aircraft. A blade design operating at lower RPM and with the span-wise loading moved inboard is shown to be significantly quieter without severe performance penalties. The employed CFD method is able to reproduce the tonal content of all blades and its dependence on hub and blade design features.

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Brown, N. (2019) Highfidelity computational fluid dynamics methods for the simulation of propeller stall flutter. A time-marching aeroelastic method developed for the study of propeller flutter is presented and validated. Propeller flutter can take many forms with stall, whirl and classical flutter being the primary responses. These types of flutter require accurate capture of the non-linear aerodynamics associated with propeller blades. Stall flutter in particular needs detailed unsteady flow modelling. With the development of modern propeller designs potentially adjusting the flutter boundary and the development of faster computing power, CFD is required to ensure accurate capture of aerodynamics. Given the lack of reliable experimental stall flutter data for propellers, the method was focused on observing the correct qualitative behaviour with a comparison made between URANS and Scale-Adaptive Simulation (SAS). Greek α s m = Model amplitude of mode m of solid s (m/kg) ζ m = Damping coefficient (-) ρ = Fluid density (kg/m 3 ) ψ s m = Normalised m th mode displacement of solid s (m/kg) ψ s = Normalised displacement of solid s (m/kg) ω m = Natural frequency of mode m Ω CV = Control volume size Subscripts i, j, k = Mesh cell indices

A time-marching aeroelastic method developed for the study of propeller flutter is presented and validated. Propeller flutter can take many forms with stall, whirl and classical flutter being the primary responses. These types of flutter require accurate capture of the non-linear aerodynamics associated with propeller blades. Stall flutter in particular, due to the highly detached nature of the flow, needs detailed unsteady flow modelling. With the development of modern propeller designs potentially adjusting the flutter boundary and the development of faster computing power, CFD is required to ensure accurate capture of aerodynamics. This paper focuses on the validation of the aeroelastic method using the Commander propeller blade.

The achievement of large areas of laminar flow over aircraft engine nacelles offers significant savings in aircraft fuel consumption. Based upon current engine configurations nett sfc benefits of up to 2% are possible. In addition the engine nacelle is ideally suited to the early inclusion of laminar flow technology, being relatively self contained with the possibility of application to existing airframes. In September 1992 a European Consortium managed by Rolls-Royce including MTU and DLR began flight testing of a natural laminar flow nacelle. This programme was later extended by R-R and DLR to flight test a hybrid laminar flow nacelle featuring boundary layer suction and insect contamination protection. The tests evaluated the effects of flight and engine environment, boundary layer transition phenomena, suction system operation and insect contamination avoidance strategies. This paper describes the global conclusions from these flight tests which are a significant milestone leading to the future application of laminar flow technology to engine nacelles.