Numerical aeroacoustic analysis of propeller designs

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 Computational Fluid Dynamics (CFD) method is able to reproduce the tonal content of all blades and its dependence on hub and blade design features

Acoustic Assessment of Twin-engined Turboprop Layout

No abstract available

Numerical modelling of the aerodynamic interference between helicopter and ground obstacles

Helicopters are frequently operating in confined areas where the complex flow fields that develop in windy conditions may result in dangerous situations. Tools to analyse the interaction between rotorcraft wakes and ground obstacles are therefore essential. This work, carried out within the activity of the GARTEUR Action Group 22 on “Forces on Obstacles in Rotor Wake”, attempts to assess numerical models for this problem. In particular, a helicopter operating in hover above a building as well as in its wake, one main rotor diameter above the ground, has been analysed. Recent tests conducted at Politecnico di Milano provide a basis for comparison with unsteady simulations performed, with and without wind. The helicopter rotor has been modelled using steady and unsteady actuator disk methods, as well as with fully resolved blade simulations. The results identify the most efficient aerodynamic model that captures the wakes interaction, so that real-time coupled simulations can be made possible. Previous studies have already proved that the wake superposition technique cannot guarantee accurate results if the helicopter is close to the obstacle. The validity of that conclusion has been further investigated in this work to determine the minimum distance between helicopter and building at which minimal wake interference occurs

Aeroacoustic simulation of modern propellers

Because of their considerably higher fuel efficiency compared to turbofans, turboprop aircraft are the best choice for short and middle-haul flights. Yet, propeller acoustic emissions need to be reduced to comply with future noise certification standards, and to improve the comfort of passengers and crew. The CFD solver of the University of Glasgow, HMB3, was first validated for propeller aerodynamics and acoustics against JORP and IMPACTA wind tunnel data, and then employed for comparing different innovative designs and installation options to identify the quietest solution. OSPL and frequency tonal spectra were directly computed from (U)RANS results. Cabin noise was estimated via experimental transfer functions. The design of the propeller is the key to decrease the emitted sound at source level. A blade design that moves the loading inboard and operates at lower rotational speed yielded relevant noise gains (up to 6 dB in OSPL) without strong performance penalties. Hub configurations meant to redistribute the acoustic energy over more frequencies did not clearly appear more pleasant for passengers. The presence of the airframe modifies the propeller inflow, and causes additional noise sources as well as sound waves reflections. The need of simulating the whole airplane in real operating conditions to accurately estimate in-flight noise was shown. For a twin-engined high-wing aircraft with propellers in phase at cruise conditions, the counter-rotating top-in layout was found the quietest, with a benefit in interior OSPL of more than 4 dB compared to co-rotating propellers. The inboard-up propeller rotation led louder noise because of the higher blade loading on the fuselage side, and of constructive sound waves interferences. The latters are instead used favorably from propeller synchrophasing, promoting noise cancellation. This strategy was shown to provide more than 3 dB of OSPL noise reduction inside the cabin on co-rotating propellers, whereas propellers in-phase appeared the best operating option for the counter-rotating top-in layout

Computational Aeroacoustic Analysis of Propeller Installation Effects

In line with the goal of cleaner and quieter aircraft, this paper investigates propeller acoustics aiming to improve turboprops noise emissions, as they represent the best choice for short and medium range flights in terms of fuel efficiency. CFD is used to analyse the propeller-airframe interaction physics, and assess propeller installation effects, for a full scale twinengined aircraft. The employed propellers represent advanced designs currently used in modern aircraft and the cases of co-rotating and counter-rotating top-in layout are considered. The URANS approach is used on grids of up to 195 M points aiming to directly extract from CFD the noise tonal content. Numerical results are first validated against modelscaled experimental data. A comparison between results of the full aircraft and a propeller in isolation is also carried out. Full aircraft predictions show significant differences in the external acoustics between port and starboard sides for the co-rotating case, with a louder noise generated by the inboard-up propeller. The counter-rotating layout shows a more regular distribution of overall noise, with on average slightly higher noise levels towards the front and the rear of the cabin. Acoustic predictions from an isolated propeller in axial flight significantly underestimate noise levels even on the fuselage sides where the aircraft masks the other propeller, showing the relevance of the propeller-airframe interactions in the evaluation of actual sound pressure levels in flight

Propeller installation effects on turboprop acoustics

Propeller installation options for a twin-engined turboprop aircraft are evaluated at cruise conditions, aiming to identify the quieter configuration. Computational fluid dynamics is used to investigate the near-field acoustics and transfer functions are employed to estimate the interior cabin noise. Co-rotating and counter-rotating installation options are compared. The effect of propeller synchrophasing is also considered. The employed method captures the complexity of the acoustic field generated by the interactions of the propeller sound fields among each other and with the airframe, showing also the importance of simulating the whole problem to predict the actual noise on a flying aircraft. Marked differences among the various layouts are observed. The counter-rotating top-in option appears the best in terms of acoustics, the top-out propeller rotation leading to louder noise because of inflow conditions and the occurrence of constructive acoustic interferences. Synchrophasing is shown to be beneficial for co-rotating propellers, specially regarding the interior noise, because of favorable effects in the interaction between the propeller direct sound field and the noise due to the airframe. An angle closer to the maximum relative blade shift was found to be the best choice, yielding, however, higher sound levels than those provided by the counter-rotating top-in layout

Forces on Obstacles in Rotor Wake – A GARTEUR Action Group

The paper describes the objectives and the structure of the GARTEUR Action Group HC/AG-22 project which deals with the basic research about the forces acting on obstacles when immersed in rotor wakes. The motivation started from the observation that there was a lack of experimental databases including the evaluation of the forces on obstacles in rotor wakes; and of both numerical and experimental investigations of the rotor downwash effects at medium-to-high separation distances from the rotor, in presence or without sling load. The four research centres: CIRA (I); DLR (D); NLR (NL); ONERA (F); and three universities: NTUA (GR); Politecnico di Milano (I); University of Glasgow (UK) created a team for the promotion of activities that could contribute to fill these gaps. In particular, both numerical and experimental investigations were proposed by the team to study, primarily, the effects of the confined area geometry on a hovering helicopter rotor, and, secondarily, the downwash and its influence on the forces acting on a load, loose or slung, at low to high separation distances from the rotor disc. The following activities were planned: a) application and possible improvement of computational tools for the study of helicopter rotor wake interactions with obstacles; b) set-up and performance of four cost-effective wind tunnel test campaigns aimed at producing a valuable experimental database for the validation of the numerical methodologies applied; c) final validation of the numerical methodologies. The project started in November 2014 and has a duration of three years

Clinical Psychology of Aging: the Italian Manifesto

In the context of Italian aging population, clinical psychology can play a crucial role in enabling older adults to cope with the multiple challenges associated with the aging process and disease-related issues. This manifesto was  written by the 'Clinical Psychology of Aging' working group, which is part of the Italian Association of Psychology (AIP) consisting of academic experts in this field  who collaborated to elaborate the contents highlighting the most relevant dimensions of the clinical psychology of aging. Specifically, the aging process was addressed from multiple points of view (i.e., theoretical perspectives, multidimensional assessment, interventions), and the role of the clinical psychologists in the National Health System along with training issues were discussed in the attempt to specify  the unique contribution  of the clinical psychology in aging

Off-label long acting injectable antipsychotics in real-world clinical practice: a cross-sectional analysis of prescriptive patterns from the STAR Network DEPOT study

Introduction Information on the off-label use of Long-Acting Injectable (LAI) antipsychotics in the real world is lacking. In this study, we aimed to identify the sociodemographic and clinical features of patients treated with on- vs off-label LAIs and predictors of off-label First- or Second-Generation Antipsychotic (FGA vs. SGA) LAI choice in everyday clinical practice. Method In a naturalistic national cohort of 449 patients who initiated LAI treatment in the STAR Network Depot Study, two groups were identified based on off- or on-label prescriptions. A multivariate logistic regression analysis was used to test several clinically relevant variables and identify those associated with the choice of FGA vs SGA prescription in the off-label group. Results SGA LAIs were more commonly prescribed in everyday practice, without significant differences in their on- and off-label use. Approximately 1 in 4 patients received an off-label prescription. In the off-label group, the most frequent diagnoses were bipolar disorder (67.5%) or any personality disorder (23.7%). FGA vs SGA LAI choice was significantly associated with BPRS thought disorder (OR = 1.22, CI95% 1.04 to 1.43, p = 0.015) and hostility/suspiciousness (OR = 0.83, CI95% 0.71 to 0.97, p = 0.017) dimensions. The likelihood of receiving an SGA LAI grew steadily with the increase of the BPRS thought disturbance score. Conversely, a preference towards prescribing an FGA was observed with higher scores at the BPRS hostility/suspiciousness subscale. Conclusion Our study is the first to identify predictors of FGA vs SGA choice in patients treated with off-label LAI antipsychotics. Demographic characteristics, i.e. age, sex, and substance/alcohol use co-morbidities did not appear to influence the choice towards FGAs or SGAs. Despite a lack of evidence, clinicians tend to favour FGA over SGA LAIs in bipolar or personality disorder patients with relevant hostility. Further research is needed to evaluate treatment adherence and clinical effectiveness of these prescriptive patterns