Effects of Inflow Forcing on Jet Noise Using Large Eddy Simulation

Lew, Phoi-Tack; Uzun, Ali; Blaisdell, Gregory A.; Lyrintzis, Anastasios S.

doi:10.2514/6.2004-516

Cited by 26 publications

(21 citation statements)

References 31 publications

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“…The center of the vortex is located at x 0 which is r 0 in our case. Studies regarding the effect of this inflow forcing on subsonic jets can be found by Lew et al 27 and Bogey and Bailly. 28 Because both the compact scheme and the spatial filter require all the data points along a given grid line to solve the linear system, a transposition strategy 13 is used for the parallelization.…”

Section: A 3-d Les Methodologymentioning

confidence: 99%

Numerical Simulation of Supersonic Jet Flows and their Noise

Blaisdell

Lyrintzis

2008

14th AIAA/CEAS Aeroacoustics Conference (29th AIAA Aeroacoustics Conference)

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Large-eddy simulations (LES) of a circular supersonic fully expanded jet and an underexpanded jet are performed. Both jets operate at a design Mach number 1.95, and the corresponding fully expanded Mach number for the underexpanded jet is 2.20. Since the simulations do not include the nozzle geometry explicitly, the effects of the inflow conditions (such as the forcing modes and shear layer thickness) on the near field statistics and far field noise are investigated. The near field data are collected from the LES and then the far field noise is computed by the Ffowcs Williams-Hawkings (FWH) surface integral method. The results show that removing the lower forcing modes increases the centerline velocity decay rate, the peak turbulence intensities, and the overall sound pressure level. However, reducing the inflow shear layer thickness has the opposite effect and achieves a better agreement with the experiments in both near field statistics and farfield noise. Similar trends hold for the underexpanded jet in near field statistics; however, the number of shock cells is underpredicted and is insensitive to the inflow conditions. This may be due to contamination by spurious numerical fluctuations caused by the shocks. Further simulations including shock capturing schemes are needed.

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Section: A 3-d Les Methodologymentioning

confidence: 99%

Numerical Simulation of Supersonic Jet Flows and their Noise

Blaisdell

Lyrintzis

2008

14th AIAA/CEAS Aeroacoustics Conference (29th AIAA Aeroacoustics Conference)

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“…This is to be compared to random perturbations of jets in the numerical literature. The latter are usually weak, at most on the order of 1% ͑see, e.g., Lew et al 19 where a non-normal random perturbation is added to the flow field inside the computational domain one jet radius downstream of the inflow or Shariff et al 15 where the initial condition is perturbed by a random term representing at most 2% of the unperturbed flow͒. In our case, the factor A = 0.001 amounts to adding a random term of f = A / ͱ ⌬t of the inflow velocity.…”

Section: Numerical Resultsmentioning

confidence: 98%

“…͑10͒. On the other hand, none of the cited papers on spatially developing turbulent flows [16][17][18][19] discusses the dependence of the applied random excitation on the time step.…”

Section: A Mathematical Frameworkmentioning

confidence: 96%

“…17 Very often this method is applied to simulating turbulent spatially evolving jets, be it directly 18 or using large eddy simulations. 19 DNSs of turbulent flows provide a huge amount of data which need a data reduction technique allowing the extraction of the physically most relevant information. For this purpose, usually the proper orthogonal decomposition 20 ͑POD͒ ͑or Karhunen-Loeve decomposition͒ is used.…”

Section: Introductionmentioning

confidence: 99%

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Receptivity of a spatially developing jet to stochastic perturbations

Saïdi

Dušek

David³

2011

Physics of Fluids

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In direct and large eddy simulations, turbulence in flows is often sustained using a random excitation. In this paper, the problem of receptivity of a linearized stable dynamical system to stochastic perturbations is reformulated in terms of the Lyapunov equation. The latter provides directly the statistical characterization of the random solution. It is shown how to describe the excitation term to obtain a time-step invariant response. The solution of the Lyapunov equation is equivalent to the spatial correlation matrix of the proper orthogonal decomposition ͑POD͒. It can thus be further post-treated to yield POD modes. The method is tested in the case of a weakly turbulent slightly heated jet by comparing the results obtained by statistical accumulation of data provided by a fully nonlinear unsteady Navier-Stokes simulation to the solution of the Lyapunov equation. The traces and POD modes are found in a very good agreement. The obtained results not only validate the method but also show that some flows may respond in an essentially linear way to random excitation and that, in this case, the direct statistical approach is more efficient and provides more reliable results than the classical Monte Carlo approach.

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“…Artificial forcing techniques used in many LES simulations (see Ref. 21) may cause spurious far-field SPLs. The centerline of the nozzle is along the x axis and y and z are lateral axes, respectively.…”

Section: Computational Setupmentioning

confidence: 99%

Unsteady numerical simulation of a round jet with impinging microjets for noise suppression

Lew

Najafi-Yazdi

Mongeau

2013

The Journal of the Acoustical Society of America

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The objective of this study was to determine the feasibility of a lattice-Boltzmann method (LBM)-Large Eddy Simulation methodology for the prediction of sound radiation from a round jet-microjet combination. The distinct advantage of LBM over traditional computational fluid dynamics methods is its ease of handling problems with complex geometries. Numerical simulations of an isothermal Mach 0.5, Re D ¼ 1 Â 10 5 circular jet (D j ¼ 0.0508 m) with and without the presence of 18 microjets (D mj ¼ 1 mm) were performed. The presence of microjets resulted in a decrease in the axial turbulence intensity and turbulent kinetic energy. The associated decrease in radiated sound pressure level was around 1 dB. The far-field sound was computed using the porous Ffowcs Williams-Hawkings surface integral acoustic method. The trend obtained is in qualitative agreement with experimental observations. The results of this study support the accuracy of LBM based numerical simulations for predictions of the effects of noise suppression devices on the radiated sound power.

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Effects of Inflow Forcing on Jet Noise Using Large Eddy Simulation

Cited by 26 publications

References 31 publications

Numerical Simulation of Supersonic Jet Flows and their Noise

Numerical Simulation of Supersonic Jet Flows and their Noise

Receptivity of a spatially developing jet to stochastic perturbations

Unsteady numerical simulation of a round jet with impinging microjets for noise suppression

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