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This paper aims at investigating and analyzing numerical simulations of landing-gear configurations of increasing complexity using the Lattice-Boltzmann solver "LaBS". The LAGOON (LAnding-Gear nOise database for CAA validatiON) project, supported by Airbus, 1, 2 provides an accurate experimental database on simplified landing-gear configurations perfectly suitable for this purpose. First, an assessment of the numerical approach accuracy is carried out on LAGOON1 configuration by comparing both aerodynamic and near-field acoustic results with the LAGOON database disclosed in the frame of the NASA BANC workshop. Then, further investigations are focused on the influence of mesh refinement, subgrid scale model and wall law parameters. Finally, the best practices obtained are applied on LAGOON2 & 3 configurations and allow to capture the impact of some geometrical components added onto LAGOON1 baseline.

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Pilot flames, created by additional injectors of pure fuel, are often used in turbulent burners to enhance flame stabilisation and reduce combustion instabilities. The exact mechanisms through which these additional rich zones modify the flame anchoring location and the combustion dynamics are often difficult to identify, especially when they include unsteady hydrodynamic motion. This study presents Large Eddy Simulations (LES) of the reacting flow within a large-scale gas turbine burner for two different cases of piloting, where either 2 or 6 percent of the total methane used in the burner is injected through additional pilot flame lines. For each case, LES shows how the pilot fuel injection affects both flame stabilisation and flame stability. The 6 percent case leads to a stable flame and limited hydrodynamic perturbations in the initial flame zone. The 2 percent case is less stable, with a small-lift-off of the flame and a Precessing Vortex Core (PVC) in the cold stabilisation zone. This PVC traps some of the lean cold gases issuing from the pilot passage stream, changes the flame stabilisation point and induces instability.

This paper aims at predicting the noise generated by flows interacting with airframe elements using unstructured LES coupled with a FW-H technique. The rod-airfoil canonical geometry 5 has been selected as a benchmark representative of such phenomena. The detailed experimental database 5 and several numerical simulations 3, 6-11 available enable an extensive validation of the proposed methodology. Similar or improved results are obtained both in the near-field (velocity profiles) and in the acoustic far-field (power spectral densities obtained with both porous and solid surfaces) compared with the best, most recent simulations. The impact of two important numerical parameters is also assessed : the spanwise dimension of the computational domain, and the sensitivity of the rod/airfoil alignment. The former improves the low frequency content of the simulated acoustic pressure, the latter only the simulated near-field in the cylinder wake. Finally best practices are drawn from this test case for future airframe industrial configurations.

Purpose-The lattice Boltzmann (LB) method offers an alternative to conventional computational fluid dynamics (CFD) methods. However, its practical use for complex turbulent flows of engineering interest is still at an early stage. In this article, a LB wallmodeled large-eddy simulation (WMLES) solver is outlined. The flow past a rod-airfoil tandem in the sub-critical turbulent regime is examined as a challenging benchmark. Design/methodology/approach-Fluid dynamics are discretized upon the LB principles. The large-eddy simulation is accounted straightforwardly by including a modeled subgrid-scale viscosity in the LB scheme, whereas a wall-law model enforces the boundary condition at the first off-wall node. This physical modeling is briefly introduced and relevant references are given for details. The flow past a rod-airfoil tandem at Reynolds number Re = 4.8 × 10 4 and Mach number Ma 0.2 is simulated on a composite multiresolution grid; the numerical setup is detailed. Unsteady aerodynamic and aeroacoustic features including spectral analysis and far-field pressure fluctuations are discussed. Findings-Extensive quantitative comparisons with both experimental and numerical reference data indicate that aerodynamic and aeroacoustic features are well captured by the LB simulation. Originality/value-Our study shows that WMLES within the LB framework provides a workable and efficient alternative to Navier-Stokes CFD solvers in the context of complex turbulent flows. The LB method permits to access an attractive turnaround time while 1 preserving engineering accuracy.

This paper aims at performing a CFD/CAA study on the LAGOON landing-gear baseline configuration using a high-order unstructured compressible LES solver chained with a Ffowcs-Williams and Hawkings analogy. Both aerodynamic and acoustic results are compared with the LAGOON database supported by Airbus and with the latest studies using block-structured meshes in terms of near-field (Wall-pressure distribution and spectra, velocity profiles) and of far-field results (Pressure spectra and directivity). The effect of grid-refinement at the wall and the use of a wall-function are also investigated. Fairly good aerodynamic and acoustic results are obtained. The grid refinement improves the results quality and increases the cut-off frequency of the near-field and far-field spectra, while wall-modeling yields mixed results. NomenclatureLES Large-Eddy Simulation DES Detached-Eddy Simulation RANS Reynolds-Averaged Navier-Stokes LBM Lattice-Boltzman Method FW-H Ffowcs-Williams and Hawkings PSD Power Spectral Density U in Free-stream velocity M a Mach number P in Free-stream static pressure T in Free-stream temperature D Wheel diameter d Upper leg diameter Re D Reynolds number related to the wheel diameter D Re d Reynolds number related to the upper leg diameter d C p Pressure coefficient u Mean streamwise velocity u rms Root-mean-squared streamwise velocity