1/ Assessment at material/component level
For LGs:
Passive FTFs (solid, wire meshes, perforated plates, Diamond-Lattice cells and metallic wool) proposed by DAv/DLR/ONERA/TUD were (i) characterized in B2A@ONERA and WAABLIEF@VKI (May-Sep 21) to calibrate numerical models, (ii) tested in A-Tunnel@TUD (Sept 21) on a LAGOON LG to validate computations without/with FTFs by ONERA/RWTH/Chalmers/DAv and (iii) tested on a generic detailed BJ trailing-arm MLG model in AWB@DLR (Oct 21/Jan 22), also computed by DAv. Finally, tests by SLS/DAv of the same MLG and FTFs at scale 1 in S2A (Feb/Oct 23) revealed discrepancies with AWB results transposed to full scale, showing a global sensitivity to scale effects.
TCD first designed local/global active air curtain via CFD to evaluate air mass rates and tune-up the designs. Several local blowing devices were tested in AWB on a LAGOON LG in Jan 22, with significant self-noise generated by the nozzles. New designs of more silent nozzles (air blade and tube) were tested in AWB (Mar 23) on a GB-MLG, with significant noise reductions.
Airbus led a DTN activity: from a detailed 2-wheel MLG designed by SLS, a low noise design accounting for integration constraints was derived, with intensive use of ProLB (LBM solver) for the local unsteady flow and a FWH method for the radiated noise. First simulations at 1/7.5th scale, validated with tests in AWB (Jul 22), underlined the physics and ranking of the main noise sources. A numerical benchmark by Airbus/ONERA/CERFACS provided best practices and compromise of accuracy vs cost. Then partners shared parametric computations at 1/4th scale of the sidestay/lockstay orientation/shape modifications. This led to a low noise design, tested at scale 1/12.5th isolated in AWB (Jan 24) and installed under wing in NWB@DNW (Apr 24), showing the numerical capability of the DTN, and its applicability to future LG. Besides, ONERA computed a 4-wheel MLG (same A/C weight) with 3 bogie angles, all globally noisier than the reference 2-wheel LG, the “toe-up” angle being the quietest.
The LG wake/flap interaction noise (observed in ARTEM) was reduced using porous materials on the flap. Flow surveys of the LG wake achieved in AWB on the ARTEM set-up validated initial RANS computations by UCFD, which fed 2 numerical simulations of the interaction noise based on (i) scale resolving simulations on the baseline by UCFD, and (ii) CAA with stochastic forcing by DLR (PIANO), with the porous inserts on the flap modeled with the Darcy-Forchheimer model, showing efficient noise reduction.
For HLDs:
14 generic/low noise slat tracks proposed by DAv/DLR/NLR (6 of them designed from RANS) were acoustically assessed (Sep 21) in AWT@NLR on DLR’s flapless 2.5D high-lift wing F16 at a 30° sweep, showing the critical acoustic role of the wing cavity, and the potential of low noise designs.
In Oct 21, porous inserts (Diamond-Lattice cells and polyurethane foam) proposed by TCD/TUD/DLR were characterized in WAABLIEF to calibrate/validate numerical models, and then tested at the slat suction side of the F16 model at 0° sweep at AAWT@UoB, showing modest noise reductions, confirmed by numerical simulations by RWTH.
In Apr-May 22, the same slat tracks and porous slats (with more inserts and materials located close to the slat trailing edge) were assessed in F2@ONERA on the full 3-element F16 model at 30° sweep with 3 slat systems (1 continuous and 2 slat side-edges). Data relying on a 120-microphone array, static pressure taps, PIV and LDV, were compared by ONERA/NLR/DAv/DLR with numerical simulations of slat track flow and noise, fairly recovering the experimental levels observed with the slat tracks.
In May-Jun 22, aeroacoustics tests at AWT@UoS of an academic wall-mounted spoiler identified the main noise sources (deflection angle, upstream boundary layer and separation bubble, turbulent wake and side edge vortices), confirmed by ProLB simulations by CERFACS/UoS. A more realistic spoiler, tested in AWB in the OPENAIR project, was also computed to validate the approach in operational conditions.
Aeroacoustic data of a classic slotted slat and 2 Krüger flaps (reference/low noise) installed on a SMR A/C model in NWB (INTONE German project) were provided to ONERA/Chalmers who achieved flow/noise numerical simulations with ProLB/STAR-CCM+, in a wing section without tracks, partially recovering the noise deltas observed between the configurations.
2/ Assessment at airframe/aircraft level
In Apr 24, the best NRTs, selected at component levels, were tested in NWB at airframe level on two semi-span generic A/C models, a SMR A/C at scale 1/15th (Airbus) and a BJ A/C at scale 1/10th (DAv). For both A/C, a baseline (no NRTs) was defined, and NRTs were tested, either one by one, or combined to maximize their effect.
Then, the measured noise reductions were extrapolated to full scale and applied to more realistic A/C platforms to evaluate the impacts in EPNdB on certification noise at approach. An assessment of the best combination of NRTs was also achieved on a SMR A/C in approach operational conditions during the full descent and showed promising results.
Finally, Airbus achieved numerical simulations with ProLB of the whole semi-span SMR model without/with the main LG, nicely recovering the moderate noise delta generated by the MLG.
