Experimental Studies on a Rudimentary Four Wheel Landing Gear

Venkatakrishnan, L.; Karthikeyan, N.; Mejia, Kevin

doi:10.2514/6.2011-354

Cited by 15 publications

(14 citation statements)

References 7 publications

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“…Here, we revert to the RLG in order to use the NAL experimental data. 19 The DES solution had σ min = 0. Below St ≈ 0.5 the wind-tunnel data appear contaminated by global fluctuations (identical at all three forward-facing points, namely 4, 5 and 6).…”

Section: Iiia2 Turbulencementioning

confidence: 99%

Sensitivity of Landing-Gear Noise Predictions by Large-Eddy Simulation to Numerics and Resolution

Spalart

Shur²,

Strelets³

et al. 2012

50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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Landing-gear noise is predicted by conducting a Detached-Eddy Simulation of the turbulent region, and extrapolating the sound to the far field using the Ffowcs-WilliamsHawkings (FWH) equation. We use the Rudimentary Landing Gear (RLG), as well as two simpler configurations. Our past results conflicted with expectations based on Curle's approximation. Even at Mach numbers near 0.1, the sound attributed to surface pressure fluctuations ("S" sound) did not agree with the sound predicted with a permeable FWH surface ("P" sound). There was an apparent "quadrupole effect." We cautiously published this finding. In further work, we have found that it is not numerically robust at the level of grid resolution we had, of the order of 18 million points for the full RLG. Specifically, the P and the S results as well as their difference decrease tangibly when some measure of upwind differencing and thus numerical dissipation is introduced in the turbulent region; this brings results close to Curle's prediction (experimental comparisons are not presented). This is although the flow field obtained with minimal numerical dissipation is free of oscillations or spectral anomalies, and appears to represent a better simulation; upwind differencing smooths out the solution. In addition, for the simpler case of an isolated axle, simulations with finer grids by a factor of 2 and then 4 in each direction also produce lower noise and weaker apparent quadrupole content, even though they contain more small-scale turbulence. We discuss this troublesome disconnect between accepted criteria for the quality of a Large-Eddy Simulation, on one hand, and the noise predicted in the far field, on the other hand. In Appendices we discuss the detailed implications of theory regarding Mach-number scaling and relevant experimental findings, in preparation for later noise comparisons, and an independent verification of our FWH code.

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Section: Iiia2 Turbulencementioning

confidence: 99%

Sensitivity of Landing-Gear Noise Predictions by Large-Eddy Simulation to Numerics and Resolution

Spalart

Shur²,

Strelets³

et al. 2012

50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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“…7a. It is relevant to note that the experimental measurements 12 were collected in a narrow 3.44D x 3.44D hard-walled wind tunnel sketched in Fig. 7b while the present calculations were carried out in a much wider channel (Fig.…”

Section: A Near-field Transient Flow Resultsmentioning

confidence: 99%

“…The RLG geometry ( Fig. 1), its dimensions and test flow conditions have been described in detail in earlier experimental and numerical studies 12,13 , which focused on predicting surface pressures and placed the model in a wind tunnel of the size of that at the National Aerospace Laboratories (NAL) in Bangalore, India 12 . In the present study, in order to allow far-field noise predictions, three of the walls are removed, and the RLG model is placed in a half space, with a plane of symmetry at the same distance as the previous wind-tunnel wall, namely 1.845 D. The post reaches this plane.…”

Section: Problem Descriptionmentioning

confidence: 99%

Rudimentary Landing Gear Noise Predictions Using Scale-Resolving Simulations

Kurbatskii

Viti

Menter

et al. 2013

51st AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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In this work we present a computational investigation of the problem of unsteady flow past a rudimentary four-wheel landing gear configuration and associated far-field noise radiation. The numerical simulations are carried out using the general purpose CFD code ANSYS Fluent. The pressure-based solver with the second-order bounded central-difference spatial discretization and second-order bounded implicit time marching scheme is applied to obtain a time-accurate solution. Compressibility effects are negligible for the Mach numbers under consideration (M < 0.3) and the flow is treated as incompressible. Two-scale resolving turbulence approaches are considered: the Delayed Detached Eddy Simulation (DDES) and Scale-Adaptive Simulation (SAS). The numerical simulation is carried out on two computational meshes with different resolutions to provide a measure of grid independence. The numerical solution recovers the unsteady generation of fine-scale turbulent content critical for accurate predictions of far-field acoustic spectra. Numerical values of pressure spectra at selected location on the landing gear are compared with experimental data, and favorable agreement at lower frequencies is found. The Ffowcs Williams and Hawkings (FW-H) model is applied to propagate acoustic waves from the source surfaces defined on all the landing gear walls into the far field, and far-field noise directivities are examined. Sound spectrum at a far-field microphone location calculated by the FW-H model is in agreement with experimental measurements at lower frequencies.

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“…The measurement allowed the identification of different flow states at low frequency. Venkatakrishnan et al 11 measured the flow around a rudimentary four-wheel landing gear. It was found that the struts strongly affect the flow field around the two in-line wheels.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulations of Single and Tandem Wheels for Aerodynamic Loads Prediction

Spagnolo

Xin

et al. 2015

22nd AIAA Computational Fluid Dynamics Conference

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The aim of this work is to improve the accuracy and efficiency of unsteady aerodynamic loads prediction of landing gears in flight conditions, as part of the UK ATI ALGAAP (Advanced Landing Gear Aero-loads and Aero-noise Prediction) project. Delayed DetachedEddy Simulations (DDES) with the Spalart-Allmaras turbulence model are performed to obtain the desired prediction improvement, both with the fully-turbulent inflow and with laminar inflow and fixed transition. The reference geometries for the current simulations are generic scaled landing-gear wheels in single and tandem configurations, which have been experimentally tested within the project. An experimental database, consisting of mean and unsteady aerodynamic loads, on-surface pressures and velocity fields from particle image velocimetry, is used for CFD validation. The results show the importance of modelling the transition in order to reproduce the experimental data in the transitional regime and to correctly capture the physical flow features. The proposed high-efficiency DDES simulations improve the accuracy of the results with respect to the standard DDES model both on single and tandem wheels. The discrepancy between simulations and experiments on the total mean drag coefficient of tandem wheels is within 7% at zero angle of attack and up to 15% at higher angles of attack.

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Experimental Studies on a Rudimentary Four Wheel Landing Gear

Cited by 15 publications

References 7 publications

Sensitivity of Landing-Gear Noise Predictions by Large-Eddy Simulation to Numerics and Resolution

Sensitivity of Landing-Gear Noise Predictions by Large-Eddy Simulation to Numerics and Resolution

Rudimentary Landing Gear Noise Predictions Using Scale-Resolving Simulations

Numerical Simulations of Single and Tandem Wheels for Aerodynamic Loads Prediction

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