Xin Zhao

Spatial interpolation methods (SIMs) are widely used in local environmental assessments, yet their computational cost and performance vary substantially across datasets. High resolution modelling of elements of local environmental studies, including pollutant concentrations and noise, is often computationally demanding. As a result, SIMs are widely used to estimate values between modelled points and construct exposure contour maps. The choice of interpolation method therefore has a direct influence on both computational efficiency and the accuracy of subsequent impact assessments.This work develops a structured framework for comparing and selecting SIMs by examining how they differ in three practical respects: how strongly they smooth or preserve sharp spatial features, how sensitive they are to the spacing of available data points, and how computationally demanding they are to apply. To demonstrate these distinctions, we analyse pollutant concentration and noise datasets using airport sites as the case study. High resolution model outputs are used as reference values, against which we evaluate interpolated estimates derived from coarser grids across a range of SIMs. This enables a systematic assessment of method behaviour under realistic sampling conditions typical of local environmental modelling.We compare commonly used SIMs including nearest neighbour, inverse distance weighting, linear and Clough–Tocher triangulation, radial basis functions and several kriging variants across multiple sampling densities. Errors relative to fine grid values are analysed together with measures of local spatial gradients, allowing us to identify when methods smooth peaks, distort steep transitions or perform reliably in more uniform regions. The study also reviews recent machine learning and hybrid interpolation approaches and summarises current software support for SIMs.The outcome has two components. First, we present a decision tree that groups SIMs according to their ability to represent sharp spatial changes, their sensitivity to spatial sampling and their computational requirements. This framework provides a general guide for method selection in local environmental assessments. Second, the case studies show that interpolation performance depends strongly on the structure of the dataset being modelled, meaning that method choice should always be verified for the specific application. Together, the framework and case study findings offer both a basis for SIM selection and insight into how different methods perform in practice when balancing accuracy and computational cost.

An open-source simulation model for aircraft noise prediction is presented and validated using backpropagated noise measurements for a state-of-the-art engine and aircraft. The validation is focused on approach procedures and was performed using ground-based noise measurements that were taken at 17 recording stations for a total of 18 consecutive flights carried out during the morning of 8 April 2021. The flights were performed using two A321neo aircraft with LEAP-1A engines. It is demonstrated that the presented noise model provides a satisfactory estimation of the source noise for varying approach configurations and flight conditions. Configurations using a greater number of high-lift devices are particularly well predicted in the mid- and high-frequency regions, whereas the lower configuration settings show greater spectral deviations, which are partly attributed to measurement uncertainties caused by the increased aircraft–microphone distance. The model can predict the overall mean total sound intensity level within a 2 dB accuracy for all configurations, while the average predicted level at each microphone differs by less than 3 dB from the measurement average, for all cases except one. Variation in aircraft speed showed to have a strong impact on the predicted total noise, which matches the well-recognized sixth-power Mach number far-field sound intensity scaling law for airframe noise models, while the measurements indicated a less significant dependency. This is mainly due to installation effects and noise reduction measures that are not included in the models. Nevertheless, the variations in the spectra of the predicted and measured noise showed similar patterns.

The inflow distortion to the fan introduced by the ingestion of the fuselage boundary layer is the most critical challenge in realizing the benefits of boundary later ingesting (BLI) concepts. Minimizing the level of distortion while maintaining the desired amount of ingested boundary layer and free stream flow is crucial in minimizing the penalties to fan efficiency and noise emissions. In this paper, a parametric sensitivity study is performed to examine the integration of two semi-buried BLI turbofans at the rear end of a typical tube-and-wing body (TWB) fuselage. The key parameters influencing BLI, such as the nacelle installation positions, wing position, fuselage length, rear fuselage shape, intake shape and operating conditions were evaluated by computational fluid dynamics (CFD). Among the investigated parameters, increasing the nacelle spanwise installation spacing improved inflow distortion by reducing the diffusion separation, but this needs to be offset against the added weight and nacelle drag. A high wing position variant showed strong interference between the wing and the nacelle, which must be avoided as this significantly increases the complexity of the inflow distortion. A moderate angle of attack (AOA) variation did not affect the fan inflow distortion but there was a tendency for interference from the wing to increase when the AOA was increased. The general conclusions from this study will be useful in the conceptual design of a similar type of BLI configuration, as well as a more comprehensive optimization of this type of aircraft–engine integration.

Key results from the EU H2020 project CENTRELINE are presented. The research activities undertaken to demonstrate the proof of concept (technology readiness level—TRL 3) for the so-called propulsive fuselage concept (PFC) for fuselage wake-filling propulsion integration are discussed. The technology application case in the wide-body market segment is motivated. The developed performance bookkeeping scheme for fuselage boundary layer ingestion (BLI) propulsion integration is reviewed. The results of the 2D aerodynamic shape optimization for the bare PFC configuration are presented. Key findings from the high-fidelity aero-numerical simulation and aerodynamic validation testing, i.e., the overall aircraft wind tunnel and the BLI fan rig test campaigns, are discussed. The design results for the architectural concept, systems integration and electric machinery pre-design for the fuselage fan turbo-electric power train are summarized. The design and performance implications on the main power plants are analyzed. Conceptual design solutions for the mechanical and aero-structural integration of the BLI propulsive device are introduced. Key heuristics deduced for PFC conceptual aircraft design are presented. Assessments of fuel burn, NOx emissions, and noise are presented for the PFC aircraft and benchmarked against advanced conventional technology for an entry-into-service in 2035. The PFC design mission fuel benefit based on 2D optimized PFC aero-shaping is 4.7%.

Aircraft and engine technology have continuously evolved since their introduction and significant improvement has been made in fuel efficiency, emissions, and noise reduction. One of the major issues that the aviation industry is facing today is pollution around the airports, which has an effect both on human health and on the climate. Although noise emissions do not have a direct impact on climate, variations in departure and arrival procedures influence both CO₂ and non-CO₂ emissions. In addition, design choices made to curb noise might increase CO₂ and vice versa. Thus, multidisciplinary modeling is required for the assessment of these interdependencies for new aircraft and flight procedures. A particular aspect that has received little attention is the quantification of the extent to which early design choices influence the trades of CO₂, NOx, and noise. In this study, a single aisle thrust class turbofan engine is optimized for minimum installed SFC (Specific Fuel Consumption). The installed SFC metric includes the effect of engine nacelle drag and engine weight. Close to optimal cycles are then studied to establish how variation in engine cycle parameters trade with noise certification and LTO (Landing and Take-Off) emissions. It is demonstrated that around the optimum a relatively large variation in cycle parameters is allowed with only a modest effect on the installed SFC metric. This freedom in choosing cycle parameters allows the designer to trade noise and emissions. Around the optimal point of a state-of-the-art single aisle thrust class propulsion system, a 1.7 dB reduction in cumulative noise and a 12% reduction in EINOx could be accomplished with a 0.5% penalty in installed SFC.

Electrification of the propulsion system has opened the door to a new paradigm of propulsion system configurations and novel aircraft designs, which was never envisioned before. Despite lofty promises, the concept must overcome the design and sizing challenges to make it realizable. A suitable modeling framework is desired in order to explore the design space at the conceptual level. A greater investment in enabling technologies, and infrastructural developments, is expected to facilitate its successful application in the market. In this review paper, several scholarly articles were surveyed to get an insight into the current landscape of research endeavors and the formulated derivations related to electric aircraft developments. The barriers and the needed future technological development paths are discussed. The paper also includes detailed assessments of the implications and other needs pertaining to future technology, regulation, certification, and infrastructure developments, in order to make the next generation electric aircraft operation commercially worthy.