Calculation of far field jet noise spectra from near field measurements with true source location

Ahuja, K. K.; Tester, Brian J.; Tanna, H. K.

doi:10.1016/s0022-460x(87)81374-3

Cited by 28 publications

(27 citation statements)

References 1 publication

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“…The grid mesh spacings are uniform with ⌬r = ⌬z = 0.065r 0 , yielding the Strouhal number St D = 8.6 for four points per wavelength. After a propagation time of t =60r 0 / u j , pressure is recorded around the jets at a distance of 60r 0 from z = r = 0, where far-field acoustic conditions are expected to apply according to experiments, 48 during periods of 300r 0 / u j for Jetnoise256, Jetring256, and Jetring512, 140r 0 / u j for Jetring256drdz, 290r 0 / u j for Jetring1024dz, and 250r 0 / u j for Jetring1024drdz. Pressure spectra are then evaluated using overlapping samples of duration 38r 0 / u j , and they are averaged in the azimuthal direction.…”

Section: E Far-field Extrapolationmentioning

confidence: 99%

Large-eddy simulation of the flow and acoustic fields of a Reynolds number 105 subsonic jet with tripped exit boundary layers

2011

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Large-eddy simulations ͑LESs͒ of isothermal round jets at a Mach number of 0.9 and a diameter-based Reynolds number Re D of 10 5 originating from a pipe are performed using low-dissipation schemes in combination with relaxation filtering. The aim is to carefully examine the capability of LES to compute the flow and acoustic fields of initially nominally turbulent jets. As in experiments on laboratory-scale jets, the boundary layers inside the pipe are tripped in order to obtain laminar mean exit velocity profiles with high perturbation levels. At the pipe outlet, their momentum thickness is ␦ ͑0͒ = 0.018 times the jet radius, yielding a Reynolds number Re = 900, and peak turbulence intensities are around 9% of the jet velocity. Two methods of boundary-layer tripping and five grids are considered. The results are found to vary negligibly with the tripping procedure but appreciably with the grid resolution. Based on analyses of the LES quality and on comparisons with measurements at high Reynolds numbers, fine discretizations appear necessary in the three coordinate directions over the entire jet flow. The final LES carried out using 252ϫ 10 6 points with minimum radial, azimuthal, and axial mesh spacings, respectively, of 0.20, 0.34, and 0.40ϫ ␦ ͑0͒ is also shown to provide shear-layer solutions that are practically grid converged and, more generally, results that can be regarded as numerically accurate as well as physically relevant. They suggest that the mixing-layer development in the present tripped jet, while exhibiting a wide range of turbulent scales, is characterized by persistent coherent vortex pairings.

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Section: E Far-field Extrapolationmentioning

confidence: 99%

Large-eddy simulation of the flow and acoustic fields of a Reynolds number 105 subsonic jet with tripped exit boundary layers

2011

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“…The grid spacings are uniform with ∆r = ∆z = 0.065r 0 , yielding St D = 8.6 for an acoustic wave at four points per wavelength. After a propagation time t ≃ 60r 0 /u j , pressure is recorded around the jets at a distance of 60r 0 from z = r = 0, where far-field acoustic conditions are expected to apply according to the experiments of Ahuja et al, 60 during a period of 250r 0 /u j . Pressure spectra are evaluated using overlapping samples of duration 38r 0 /u j , and they are averaged in the azimuthal direction.…”

Section: Far-field Extrapolationmentioning

confidence: 99%

Influence of nozzle-exit boundary-layer profile on high-subsonic jets

Bogey

Marsden

2014

20th AIAA/CEAS Aeroacoustics Conference

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The influence of the nozzle-exit boundary-layer profile on high-subsonic round jets is investigated by performing compressible large-eddy simulations of four jets using lowdissipation numerical schemes. The jets are isothermal, and have a Mach number of 0.9 and a diameter-based Reynolds number of 5 × 10 4 . They originate from a pipe nozzle in which a trip-like forcing is applied. In that way, they exhibit, at the exit section, around 6% of peak turbulence intensity and boundary-layer velocity profiles characterized by a momentum thickness of about 2.8% of the nozzle radius, yielding a Reynolds number around 700, and by shape factors equal to 1.68, 1.77, 2.01 and 2.36. The results from the fourth case with a laminar velocity profile differ significantly from those from the three first cases with transitional profiles, whose accuracy is shown by a grid refinement study. Clear trends are thus identified when the shape of the exit boundary-layer profile changes from laminar to turbulent. Higher azimuthal modes and higher Strouhal numbers are found to predominate, respectively, at the pipe exit close to the wall and early on in the mixing layers. The latter appear to develop more slowly, leading to a longer potential core, and weaker velocity fluctuations are obtained in the shear layers and on the jet axis. Finally, lower noise levels are generated in the acoustic field.

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“…The grid spacings are uniform with r = z = 0.065r 0 , yielding St D = 8.6 for an acoustic wave at four points per wavelength. After a propagation time of t = 60r 0 /u j , pressure is recorded around the jets at a distance of 60r 0 from z = r = 0, where far-field acoustic conditions are expected to apply according to the experiments of Ahuja et al, 61 during a period of 250r 0 /u j . Pressure spectra are evaluated using overlapping samples of duration 38r 0 /u j , and they are averaged in the azimuthal direction.…”

Section: Far-field Extrapolationmentioning

confidence: 99%

Effects of moderate Reynolds numbers on subsonic round jets with highly disturbed nozzle-exit boundary layers

2012

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Particle transport in a turbulent boundary layer: Non-local closures for particle dispersion tensors accounting for particle-wall interactions Phys. Fluids 24, 103304 (2012) Convection and reaction in a diffusive boundary layer in a porous medium: Nonlinear dynamics Chaos 22, 037113 (2012) Symmetry analysis and self-similar forms of fluid flow and heat-mass transfer in turbulent boundary layer flow of a nanofluid Phys. Fluids 24, 092003 (2012) Detuned resonances of Tollmien-Schlichting waves in an airfoil boundary layer: Experiment, theory, and direct numerical simulation Phys. Fluids 24, 094103 (2012) Additional information on Phys. FluidsThe effects of moderate Reynolds numbers on the flow and acoustic fields of initially highly disturbed isothermal round jets at Mach number M = 0.9 and diameter-based Reynolds numbers Re D between 2.5 × 10 4 and 2 × 10 5 are investigated using largeeddy simulation under carefully controlled conditions. To the best of our knowledge, this is the first comprehensive study of its kind. The jets originate at z = 0 from a pipe nozzle of radius r 0 , in which a tripping procedure is applied to the boundary layers. At the nozzle exit, laminar-like mean velocity profiles of thickness δ 0.15r 0 and momentum thickness δ θ 0.018r 0 , yielding Reynolds numbers Re θ varying from 256 to 1856 depending on Re D , and peak turbulence intensities around 9% of the jet velocity, are thus obtained. As the Reynolds number increases, the mixing layers develop more slowly, with smaller integral length scales and lower levels of velocity fluctuations. The axial profiles of turbulence intensities become smoother, showing a clear overshoot around z = 2r 0 at Re D = 2.5 × 10 4 , but a monotonical growth at Re D = 2 × 10 5 . Velocity spectra downstream of the nozzle exit also broaden with Re D , as expected. Large-scale components usually observed in turbulent boundary layers and shear layers, characterized by Strouhal numbers St θ 0.013 around z = r 0 and by azimuthal spacings λ θ δ, remain dominant, although the contribution of fine-scale structures with λ θ ≤ δ/2 strengthens. Moreover, with rising Re D , the jet potential core lengthens slightly, but the flow properties do not change significantly farther downstream. Finally, lower sound pressure levels are generated, with a decrease of about 2 dB over the range of Re D considered. C 2012 American Institute of Physics.

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Calculation of far field jet noise spectra from near field measurements with true source location

Cited by 28 publications

References 1 publication

Large-eddy simulation of the flow and acoustic fields of a Reynolds number 105 subsonic jet with tripped exit boundary layers

Large-eddy simulation of the flow and acoustic fields of a Reynolds number 105 subsonic jet with tripped exit boundary layers

Influence of nozzle-exit boundary-layer profile on high-subsonic jets

Effects of moderate Reynolds numbers on subsonic round jets with highly disturbed nozzle-exit boundary layers

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