Hybrid electric propulsion is a promising solution to reduce aircraft emissions, thus improving the sustainability of the air transport. In this work, a hybrid aircraft configuration with a rear-mounted boundary layer ingestion (BLI) engine has been investigated. The partial embedding of the engine into the fuselage generates a distortion of the ingested inflow causing additional tonal and broadband BLI noise sources, and, at the same time, alters the existing one, such as the rotor–stator interaction noise (RSI). This work is focused on the tonal RSI noise modeling, with and without the distortion generated by the BLI, and the far-field propagation including the acoustic masking contribution due to the engine–fuselage integration. As the main result, this work shows the contributions of BLI and the engine–aircraft integration on the RSI noise. Both effects should be properly taken into account in the early aircraft design stage for an effective noise reduction even at ground level.

Over the past two decades, there has been a renewed interest in the development of a new generation of supersonic aircraft for civil purposes that could potentially succeed Concorde. However, the noise annoyance is still considered one of the hampering factors to meet public consensus. This paper aims at revealing the potential of numerical simulations to predict sonic boom signature in Near Field at early design stages. In particular, the paper further demonstrates the applicability of the numerical approach proposed by NASA and other partners during the Sonic Boom Prediction Workshops held between 2014 and 2021, to compute the pressure signature of aircraft in the zone close to it. The results highlight the suitability of the approach (1) to capture the impact of aircraft flight condition variations on the sonic boom signature, (2) to enable the characterization of novel aircraft layout, including Mach 5 waverider configuration, (3) to provide near-field shock wave noise predictions that can be used to evaluate shock propagation, on-ground signature analyses, and annoyance assessment.

Scientific research studies on jet noise generation have been ongoing since the early 1950s, when turbojets were first used in commercial aircraft. Several numerical methods have been developed with the aim of reducing the environmental issues related to the impact of jet noise on community annoyance. Among them, the development of fast and comprehensive tools for jet noise prediction captured the attention of researchers and engineers, being very useful in the preliminary design phase of aircraft engines. This work deals with an extensive survey of James R. Stone’s models, initially formulated for the National Aeronautics and Space Administration (NASA) by Modern Technologies Corporation (MTC), and their implementation in a contemporary numerical framework. The models and their implementation are validated by simulating different engine settings and nozzle configurations taken from the literature with the main scope of highlighting the strengths and weaknesses of the different semi-empirical formulations and setting guidelines for their effective use during the design phases of the next generation of supersonic aircraft.

This paper investigates the effects of the interaction between an under-expanded supersonic jet and a flat plate on screech generation. The plate is installed parallel to the jet axis and an experimental investigation is made for several configurations corresponding to different radial distances of the plate, H , from the nozzle axis. Acoustic measurements are carried out to evaluate the plate impact on jet aeroacoustics. The results show that, when the radial distance is less than 1.5 nozzle diameters, the plate substantially alters the staging dynamics between modes A1 and A2 and between modes B and C. Specifically, the plate induces an extinction of modes A2 and C together with an extension of modes A1 and B. The extent of flow conditions for which the extinction of modes A2 and C is observed is dependent on the jet-plate distance, the smaller the distance the wider the range of flow conditions. Furthermore, the plate induces a frequency splitting of mode B for the smallest jet-plate distance, that is, $$H=0.7D$$ H = 0.7 D . A time-frequency analysis is performed to explore in detail the staging dynamics between A1 and A2 modes. The study shows that the jet experiences a complete suppression of mode A2 for $$H=0.7D$$ H = 0.7 D and an intermittent switch from A1 to A2 modes as the jet-plate radial distance is increased. Finally, schlieren measurements are conducted to assess whether the observed modifications of the screech behaviour might be associated with changes of the shock-cell structure. The analysis reveals that for $$H=0.7D$$ H = 0.7 D the surface induces an attenuation of the amplitude of the secondary wavenumber peak of the shock-cell structure, thus providing a possible explanation of the A2 mode suppression observed in the noise spectra.

This paper presents a comparative analysis of simplified and high-fidelity sonic boom prediction methods to assess their applicability in the conceptual design of supersonic aircraft. The high-fidelity approach combines Computational Fluid Dynamics (CFD) for near-field shock analysis with ray-tracing and the Augmented Burgers Equation for far-field propagation through a non-uniform atmosphere, whereas the simplified Carlson method uses analytical approximations for rapid predictions. The comparison across selected climb, cruise, and descent conditions for a supersonic reference aircraft shows that the Carlson method captures general trends in sonic boom behavior, such as changes in peak overpressure and signal duration with varying Mach number and altitude. However, significant deviations are noted under realistic atmospheric conditions, highlighting limitations in the simplified model’s accuracy. Common psycho-acoustic metrics were evaluated to assess the potential annoyance on the ground. The results demonstrate that while the simplified method is effective for early-stage design assessments, the high-fidelity model is essential for precise sonic boom characterization under realistic conditions, particularly for regulatory and community impact evaluations.