This paper contributes to the prediction of aircraft noise. The framework of our study is based on a comprehensive analysis, which includes sub-models for airframe, propulsion and propeller noise. The sources models are complemented by various accounts of interference phenomena, including fuselage scattering, propeller shielding, wing and flap effects. The propagation of the acoustic pressures from the noise sources is done through a number of additional sub-models, which include spherical spreading, Doppler effects, ground reflection, shear winds and temperature gradients through the atmosphere. We present some fly-over noise data. The data include measurements by 13 microphones at community locations, meteorological data, and flight recorder data packs, which provide the complete state of the aircraft along the noise trajectory. Examples of verification are shown for the turboprop airplane Dash8-Q400, both on approach and departure. A sensitivity analysis is carried out to investigate the importance of the uncertainty effects, which are split between internal (aircraft and propulsion), external (atmospheric environment), and aircraft position.

The hovering performance and the lifting capability of tiltrotor aircraft are strongly affected by the aerodynamic interaction between wing and rotors. The tiltwing concept represents a promising technology to increase the hover performance by reducing the wing-rotor interference. The present work describes an experimental activity carried out on a ¼ scaled tiltwing aircraft half-model to achieve a detailed insight about the main issues characterising the aerodynamic interaction between wing and rotor in hover. The results of the experimental campaign, including both force measurements and Particle Image Velocimetry surveys, enabled to evaluate both the aircraft performance for different configurations of the tilting wing and to achieve a detailed insight about the flow physics of the rotor wake in the interaction with the wing. The test activity provided a comprehensive experimental database that was obtained over a not confidential aircraft configuration.

The flow inside a constant-width wind-tunnel contraction is simulated by solving the Reynolds-Averaged Navier-Stokes equations with an eddy-viscosity turbulence model. The results show the presence of longitudinal vortices near the sidewalls centreline. This confirms a former hypothesis involving the generation of skew-induced longitudinal vorticity within the sidewalls boundary layers. Detailed analysis reveals that the flow structure is influenced by viscous effects in the boundary layers and streamline curvature in the potential flow. Three-dimensional boundary-layer profiles on the contraction sidewall are analysed in the framework of the streamline co-ordinate system and its associated hodographic diagram. The resulting profiles help understand the generation of secondary flows and the associated longitudinal vorticity.

A numerical study was conducted to analyse the performance of different turbulence models and different turbulence intensities and turbulence length scales specified for the boundary condition of the inflow to the internal compression flow field of a typical supersonic inlet. The effect of the back-pressure ratio on the properties of the flow field was also investigated. Computational results obtained by the commercial software FLUENT, which is used to solve the full two-dimensional Reynolds-averaged Navier-Stokes equations, were validated through both graphical and quantitative comparisons with previously published experimental data. The two-equation models that were considered in this study are the RNG k-ε, realisable k-ε, standard k-ε, and SST k-ω turbulence models. The RNG k-ε model had the best performance among the four models and predicted good wall pressure distributions. The best agreement between the predicted results and experimental data was obtained when either the default values of the freestream turbulence intensity and length scale in the FLUENT solver were used, or the empirical formula was used to calculate the two parameters of the freestream turbulence properties. The shock wave pattern varied between the oblique mode and the fully developed normal mode with increasing back-pressure ratio, and the unstart phenomenon occurred when the back-pressure ratio was sufficiently high.

This paper presents the concept of custom-optimised departure profiles, as an advanced form of noise abatement departure procedures. This concept relies on fixed routes in combination with individually optimised vertical departure profiles. Although the use of fixed ground tracks results in some loss in environmental performance, the high degree of complexity associated with free routing is eliminated as well, leading to a concept that does not appear to be incompatible with today’s Air Traffic Control (ATC) principles. By using a primitive form of trajectory negotiation between airline and ATC, selected flights can be allowed to perform an optimised departure without interfering with non-participating traffic. Apart from the concept itself, this paper also describes the departure profile optimisation tool, which is based on a previously developed trajectory optimisation framework called NOISHHH. Finally, in a numerical example, a current standard ICAO-A procedure is compared with two optimised profiles for a Boeing 737 departure from Amsterdam Airport. Fuel burn, noise impact and the required flight time to a specified point are compared for the three departure profiles. It is shown that the custom-optimised departure profiles have the potential to both reduce fuel burn as well as noise exposure, relative to the ICAO-A procedure.

In this article, the effect of on-surface flow visualisation (SVF) techniques on measured loads over an airfoil are explored. Titanium dioxide based mixture effects on the lift and drag coefficient are experimentally quantified at low Reynolds numbers by recording the time history as the patterns evolve and freeze. With statistical comparison based on Student’s t-distribution method, it was determined that the effect on the drag coefficient was minimal but the lift coefficient was slightly attenuated. Additionally, it was observed that at high angles-of-attack the temporal history of the flow as the wind tunnel ramps up may alter the steady-state flow field in the presence of a SFV mixture.