Multigrid acceleration of a high-resolution computational aeroacoustics scheme

Özyörük, Yusuf; Long, Lyle N.

doi:10.2514/3.13522

Cited by 4 publications

(9 citation statements)

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“…13 ' 14 The development of the time-domain acoustic impedance condition is summarized here and more details can be found in Ozyoruk and Long. 4 The two important properties of the z-transform 13 ' 16 are the time-shifting and convolution, similar to the Fourier transform. If <j[nAi] represents the nth timediscrete sample of the continuous variable q(t), the timeshifting property is given by…”

Section: Impedance Conditionmentioning

confidence: 99%

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Impedance boundary conditions for time-domain computational aeroacoustics methods

Özyörük

Long²

1997

35th Aerospace Sciences Meeting and Exhibit

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A time-domain impedance condition method has been developed for computational aeroacoustics (CAA) applications. The basis for this method is the standard impedance condition stated in the frequency domain as the particle displacement continuity equation. The development of the time-domain impedance condition follows the relations among the frequency, z-, and discrete-time domains and a rational function representation of the impedance in the z-domain. The resultant impedance condition is finite, infinite-impulse,response type, digital filter operations in the time domain, which is suitable to CAA methods. This paper describes the present approach and discusses the time-domain numerical simulations of the NASA Langley flow-impedance tube with a constant depth ceramic tubular liner. Excellent agreement is shown with experimental Abstract A time-domain impedance condition method has been developed for computational aeroacoustics applications. The basis for this method is the standard impedance condition stated in the frequency domain as the particle displacement continuity equation. The development of the time-domain impedance condition follows the relations among the frequency, z-, and discrete-time domains and a rational function representation of the impedance in the z-domain. The resultant impedance condition is finite, infinite-impulse-response type, digital filter operations in the time-domain, which is suitable to CAA methods. This paper describes the present approach and discusses the time-domain numerical simulations of the NASA Langley flow-impedance tube with a constant depth ceramic tubular liner. Excellent agreement is shown with experimental data at various frequencies and flow conditions.

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Section: Impedance Conditionmentioning

confidence: 99%

“…(4) and (5), the frequency-domain impedance condition (Eq. (1)) or the z-transform of its inverse Fourier transform may be written in the zdomain, suppressing the space dependence for brevity, as…”

Section: Impedance Conditionmentioning

confidence: 99%

Impedance boundary conditions for time-domain computational aeroacoustics methods

Özyörük

Long²

1997

35th Aerospace Sciences Meeting and Exhibit

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“…The evolution of parallel distributed computing makes permissible the simultaneous investigation of the forward and aft radiation arcs of an engine with fine spatial resolution. An efficient implementation of the moving surface Kirchhoff formula of Farassat and Myers [7] permits the prediction of far-field noise [6,8,10]. In this paper, noise generation mechanisms are analytically specified as source terms that mimic the superposition of multiple modes and harmonics related to the blade passage frequency.…”

Section: Aiaa-2000-1943 2 Ahujamentioning

confidence: 99%

“…Unfortunately, the very characteristics of low dispersion and dissipation, that make the scheme suitable to simulation of wave propagation processes, hinder convergence to steady state. The convergence problem is alleviated in our method through the use of multigrid acceleration, [10] wherein the low frequency numerical modes are aliased as high frequency modes on successive grids of varying coarseness. This is particularly attractive in acoustic problems with a mean flow, because of the high resolution nature of the grid that is needed to resolve acoustic frequencies of interest.…”

Section: Multigrid Convergence Accelerationmentioning

confidence: 99%

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Computational simulations of fore and aft radiation from ducted fans

Ahuja

Özyörük

Long

2000

6th Aeroacoustics Conference and Exhibit

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*In this paper, we extend the work of Ozyoruk and Long, for predicting farfield noise from ducted fans using a higher order coupled Euler/Navier-Stokes solver along with a Kirchhoff formulation, to full engine configurations on distributed parallel computers. Incorporating the exhaust along with the inlet raises many issues relating to appropriate grid topologies, multigrid acceleration and the unsteady numerics. These issues are addressed in this paper and simulations pertaining to a realistic engine geometry are presented. Qualitative comparisons are in good agreement with results from a frequency domain code, pertaining to radiation from a dipole in a cylinder. Simulations relating to radiation from an engine geometry, and with and without the centerbody, with and without mass flow are also shown.

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Surface Integral Methods in Computational Aeroacoustics—From the (CFD) Near-Field to the (Acoustic) Far-Field

Lyrintzis¹

2003

International Journal of Aeroacoustics

235

124

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A review of recent advances in the use of surface integral methods in Computational AeroAcoustics (CAA) for the extension of near-field CFD results to the acoustic far-field is given. These integral formulations (i.e. Kirchhoff's method, permeable (porous) surface Ffowcs-Williams Hawkings (FW-H) equation) allow the radiating sound to be evaluated based on quantities on an arbitrary control surface if the wave equation is assumed outside. Thus only surface integrals are needed for the calculation of the far-field sound, instead of the volume integrals required by the traditional acoustic analogy method (i.e. Lighthill, rigid body FW-H equation). A numerical CFD method is used for the evaluation of the flow-field solution in the near field and thus on the control surface. Diffusion and dispersion errors associated with wave propagation in the far-field are avoided. The surface integrals and the first derivatives needed can be easily evaluated from the near-field CFD data. Both methods can be extended in order to include refraction effects outside the control surface. The methods have been applied to helicopter noise, jet noise, propeller noise, ducted fan noise, etc. A simple set of portable Kirchhoff/FW-H subroutines can be developed to calculate the far-field noise from inputs supplied by any aerodynamic near/mid-field CFD code.

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Multigrid acceleration of a high-resolution computational aeroacoustics scheme

Cited by 4 publications

References 0 publications

Impedance boundary conditions for time-domain computational aeroacoustics methods

Impedance boundary conditions for time-domain computational aeroacoustics methods

Computational simulations of fore and aft radiation from ducted fans

Surface Integral Methods in Computational Aeroacoustics—From the (CFD) Near-Field to the (Acoustic) Far-Field

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