Summary of the LAGOON Solutions from the Benchmark problems for Airframe Noise Computations-III Workshop

Abstract

and the BANC-III Category 5 LAGOON Team The Benchmark for Airframe Noise Computations (BANC) has been initiated by the BECAN Technical Discussion Group under AIAA. This continuous framework, mainly impulsed by NASA LaRC, aims at evaluating numerical methods for the simulation of unsteady flows and aerodynamic noise radiated by airframe components such as airfoil trailing edges, landing gears and high lift devices. In this context, eight test-cases are proposed, with problem statements relying on extended experimental databases. The 2-wheel LAGOON landing gear is one of them. Originally designed and tested in the homonym project funded by Airbus-France, it has a simplified shape, compatible with a wide range of numerical methods, although involving complex physics. This paper summarizes seven submissions that were presented in this category at the Third BANC Workshop in Atlanta in June 2014. Researchers employed various block-structured, unstructured and embedded Cartesian ("octree") grids and large computational resources to simulate the flow and radiated noise. The solutions are compared against each other and with experimental data gathered in two Onera's windtunnels, F2 for aerodynamic data and CEPRA19 for acoustic data. Overall, all simulations captured the main features of the unsteady flow and radiated noise, including cavity resonances occurring between the wheels. The acoustic spectra and directivity diagrams of overall sound pressure levels are in fair agreement with experiment, although a significant dispersion can be observed between all contributions. Nomenclature D wheel diameter (D = 300 mm) W wheel (tyre) width (W = 88 mm) S wheelbase or spanwise distance between the wheel's median planes (S = 198 mm) D a axle diameter (D a = 44 mm) D ml main leg lower diameter (D ml = 55 mm) D mh main leg upper diameter (D mh = 71 mm) M Mach number p pressure U

Simulations of LAGOON landing-gear noise using Lattice Boltzmann Solver

“…19 Solver performance data has been communicated in the frame of the BANC-III workshop. 22 Resulting turnover time is almost an order of magnitude faster than other classical LES approaches. Ongoing code optimizations indicate that a supplementary factor 2 in code performance is reachable in the near future.…”

Noise Characterization of a Full-Scale Nose Landing Gear

“…Hybrid methods, combining, for example, detached-eddy simulation [20] with the Ffowcs Williams-Hawkings analogy [21], allow realistic landing-gear models to be numerically modeled [22,23], and entirely different approaches using lattice Boltzmann methods [24] seem to be able to dramatically decrease computational times, allowing larger and larger models to be analyzed. However, these numerical methods and others are still in development and need to be validated against experimental results provided by dedicated datasets such as the Benchmark Problems for Airframe Noise Computations initiative [25]. This paper presents experimental results from the Clean Sky funded ALLEGRA "Advanced Low Noise Landing (Main and Nose) Gear for Regional Aircraft" project.…”

The Ability of a Weakly Compressible Solver to Predict Landing Gear Noise with Flow-Acoustic Interactions

“…These trends include: 1) higher cut-off frequencies for far-field noise spectra than those for surface pressure spectra; 2) higher cut-off frequency at overhead and downstream microphones on sideline arc; 3) less under-prediction beyond the cut-off frequency on sideline arc; 4) over-predicted tonal peak at Microphone 3 on sideline arc. For 1) Manoha and Cauelle 18 gave an explanation that small, local eddies in the near-field that contributed to the surface spectra at higher frequencies are less responsible for far-field noise. For trends 2), 3) and 4) no existing hypotheses are given, but it's suspected that installation effects brought by the mounting plane, the inlet and outlet of the wind tunnel might play a role in it.…”

“…A shear layer refraction correction by Amiet and an atmospheric absorption correction have been applied to these acoustic data. Numerical predictions and experimental measurements of this configuration were summarised by Manoha and Caruelle 18 for the third workshop of Benchmark problems of Airframe Noise Computations (BANC-III).…”