Noise Radiated by a High-Reynolds-number 3-D Airfoil (original) (raw)
Related papers
Direct Noise Computation of the Turbulent Flow Around a Zero-Incidence Airfoil
AIAA Journal, 2008
A large eddy simulation of the flow around a NACA 0012 airfoil at zero incidence is performed at a chord-based Reynolds number of 500,000 and a Mach number of 0.22. The aim is to show that high-order numerical schemes can successfully be used to perform direct acoustic computations of compressible transitional flow on curvilinear grids. At a Reynolds number of 500,000, the boundary layers around the airfoil transition from an initially laminar state to a turbulent state before reaching the trailing edge. Results obtained in the large eddy simulation show a well-placed transition zone and turbulence levels in the boundary layers that are in agreement with experimental data. Furthermore, the radiated acoustic field is determined directly by the large eddy simulation, without the use of an acoustic analogy. Third-octave acoustic spectra are compared favorably with experimental data.
Direct Noise Computation around a 3-D NACA 0012 airfoil
12th AIAA/CEAS Aeroacoustics Conference (27th AIAA Aeroacoustics Conference), 2006
A Large Eddy Simulation of the flow around a NACA 0012 airfoil at a Reynolds number of 500,000 is presented. At this Reynolds number, the boundary layers transition from an initially laminar state to a turbulent state before reaching the trailing edge. Results obtained in this LES show a well-placed transition zone, and turbulence levels in good agreement with experimental data. Furthermore, the radiated acoustic field is computed directly in the same computation, which should allow future detailed examinations of the noise radiated by such a flow configuration.
Computation of unsteady flow and aerodynamic noise of NACA0018 airfoil using large-eddy simulation
International journal of heat and fluid flow, 2006
The flow field around a symmetrical NACA airfoil in the uniform flow under generation of noise was numerically studied. The numerical simulation was carried out by a large-eddy simulation that employs a deductive dynamic model as the subgrid-scale model. The results at small angle of attack a = 3-6°indicate that the discrete frequency noise is generated when the separated laminar flow reattaches near the trailing edge of pressure side and the strong instability thereafter affects positive vortices shed near the trailing edge. The quasiperiodic behavior of negative vortex formation on the suction side is affected by the strength and the periodicity of positive vortices near the trailing edge. The computation using aero-acoustic analogy indicates the primary discrete peak at the Strouhal frequency (=2f AE d/U 0) of 0.15 by the vortex shedding from the trailing edge, which is in a close agreement with the experiment.
Influence of turbulence modeling on airfoil unsteady simulations of broadband noise sources
11 th AIAA/CEAS …, 2005
In the process of simulating the trailing edge noise of an airfoil, performing the unsteady simulations of these broadband noise sources cheaply and accurately remains a major challenge. In the present study, two different fine turbulent unsteady simulations are tested on a thin controlled diffusion airfoil at low speed and low angle of attack. The flow conditions correspond to a recent aeroacoustic experiment run in the large ECL anechoic open-jet windtunnel for which detailed wall pressure and wake velocity measurements are available at the same time as the far field acoustic sound. The first turbulence model used is a Large Eddy Simulation with the standard Smagorinsky sub-grid scale model, the second one is a k--based Detached Eddy Simulation with the same sub-grid scale model. In order to stick with our objective of a simulation on a single fast PC workstation, several grid refinements in all directions have also been tested. The present final topology has up to six different grid levels. The major flow features are captured by the Large Eddy Simulation and the mean flow quantities compare favorably with the measurements. Significant differences are observed with the Detached Eddy Simulation which fails to capture the experimental short laminar separation bubble at the leading edge and consequently misses the transition point. The Large Eddy Simulation overpredicts the size of this separation bubble and the use of the MARS scheme necessary for stability reason on all the grids tested, also prevented a good prediction of the wall pressure fluctuations close to the trailing edge and therefore consequent noise predictions. This study therefore stresses the high sensitivity of such simulations of low speed transitional flows over thin airfoils.
Wall-Resolved Large Eddy Simulation over NACA0012 Airfoil
International Journal of Aerospace Sciences, 2013
The work presented here forms part of a project on Large-Eddy Simu lation (LES) of aeroengine aeroacoustic interactions. In this paper we concentrate on LES of near-field flo w over an isolated NA CA0012 airfo il at zero angle of attack with Re c =2e 5 . The pred icted unsteady pressure/velocity field is used in an analytically-based scheme for far-field trailing edge noise prediction. A wall resolved implicit LES or so-callednumerical Large Eddy Simu lation (NLES) approach is emp loyed to resolve streak-like structure in the near-wall flow regions. The mean and RMS velocity and pressure profile on airfoil surface and in wake are validated against experimental data and computational results fro m other researchers. The results of the wall-resolved NLES method are very encouraging. The effects of grid-refinement and h igher-order nu merical scheme on the wall-resolved NLES approach are also discussed. smth ctr conv J J J 1 ε + = (7) conv J , ctr J , smth J represents the interface flu x, its central difference term and s moothing term, respectively.
Aerodynamic Noise Prediction for a Rod-Airfoil Configuration using Large Eddy Simulations
20th AIAA/CEAS Aeroacoustics Conference, 2014
Aerodynamic noise produced by aerodynamic interaction between a cylinder (rod) and an airfoil in tandem arrangement is investigated using large eddy simulations. Wake from the rod convects with the flow, impinges of the airfoil to produce unsteady force which acts as a sound source. This rod-airfoil interaction problem is a model problem for noise generation due to inflow or upstream-generated turbulence interacting with a turbomachine bladerow or a wind turbine rotor. The OpenFoam and Charles (developed by Cascade Technologies) solvers are chosen to carry out the numerical simulations. The airfoil is set at zero angle of attack for the simulations. The flow conditions are specified by the Reynolds number (based on the rod diameter), Red = 48 K, and the flow Mach number, M = 0.2. Comparisons with measured data are made for (a) mean and root-mean-squared velocity profiles in the rod and airfoil wakes, (b) velocity spectra in the near field, and (c) far-field pressure spectra and directivity. Near-field flow data (on-and off-surface) is used with the Ffowcs Williams-Hawkings (FW-H) acoustic analogy as well as Amiet's theory to predict far-field sound. Disciplines
Direct Numerical Simulation of the Self-Noise Radiated by an Airfoil in a Narrow Stream
18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference), 2012
A direct numerical simulation (DNS) is conducted for the first time of an airfoil that is embedded in a wind-tunnel flow at a realistically high Reynolds number of Rec = 150, 000, based on the chord length. The nominal wind-tunnel speed corresponds to a Mach number of M = 0.25. The simulation domain comprises only the near field around the airfoil; the aerodynamic effect of the wind tunnel is included by using an appropriate set of inflow boundary profiles-a technique that has been used successfully in previous numerical airfoil studies by the authors of this paper. The boundary layer on the airfoil suction side is tripped using a purposely developed immersed-boundary method (IMBM). The results of this simulation are compared to an incompressible large-eddy simulation (LES) and experimental data. Both simulation approaches yield very good predictions of the steady and unsteady flow field and the acoustic far field. * Postdoctoral Associate, winklerj@bu.edu, AIAA member † Senior Lecturer, sandberg@soton.ac.uk, AIAA senior member ‡ Professor, stephane.moreau@usherbrooke.ca, AIAA member
CFD Letters, 2019
Airfoil Leading Edge noise is generated due to impingement of turbulent structures on the airfoil surface. The rod-airfoil configuration is a benchmark configuration for the leading edge noise and their noise calculation by computer simulation has been progressively investigated to the extend that it is comparable with the experiment. This paper presents the noise results finding between two turbulent models and their comparison with the experimental results. The two turbulent models are Large-eddy simulation (LES) and Delayed Detached-Eddy simulation (DDES). DDES can give good noise results with appropriate number of meshing grids with shorter time-span if compared to the LES. This study proposes to use DDES results for further rod-airfoil noise analysis.
LES of the trailing-edge flow and noise of a controlled-diffusion airfoil at high angle of attack
Large-eddy simulations (LES) of flow over a low-speed airfoil at high angle of attack (15 • ) are performed using two different flow solvers, Fluent and CDP, on the same fine structured mesh, whose density was previously shown to provide a reasonably accurate trailing-edge flow for noise predictions at a lower incidence of 8 • . These simulations are compared with detailed pressure measurements made using flush-mounted remote microphone probes for validation and with the previous 8 • results to assess the effect of the fan-operating condition on sound radiation. Excellent agreement is found on the mean wall-pressure coefficient for the Fluent LES. The agreement on the wall-pressure spectra is satisfactory beyond 1 kHz. The observed discrepancies at low frequencies are similar at both incidences. They are shown to have a small impact on the acoustic predictions, which compare favorably with the anechoic wind tunnel measurements. On the contrary, the CDP run shows some extra large structure burst on the suction side and a flapping of the separated shear layer born at the leading edge. This triggers a too-large low-frequency content compared to experiment. † Von Karman Institute, FRIA fellowship, Brussels, Belgium
Large Eddy Simulation of Turbulent Flow Over an Airfoil Using Both Structured and Unstructured Grids
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