An iterative finite element-integral technique for predicting sound radiation from turbofan inlets in steady flight

Horowitz, S. J.; Sigman, R. K.; Zinn, B. T.

doi:10.2514/3.9429

Cited by 17 publications

(16 citation statements)

References 11 publications

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“…For finite element applications of kinematic conditions in flow acoustics, see for instance Refs. [32,[39][40][41][42][43][44][45]. Table 4 gives some standard literature results for the dynamic condition.…”

Section: Myers Approach For Eulerian Perturbationsmentioning

confidence: 99%

Jump conditions for unsteady small perturbations at fluid–solid interfaces in the presence of initial flow and prestress

Treyssède¹,

Tahar²

2009

Wave Motion

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a b s t r a c tThe goal of this paper is to investigate jump conditions for unsteady small perturbations at impermeable interfaces, slip or bonded, plane or not, between fluids and structures in the presence of initial flow and prestress. Based on conservative equations obtained from a mixed Eulerian-Lagrangian description, interface conditions are first derived in an elegant and straightforward manner thanks to the concept of generalized functions in distribution theory. These conditions are validated with exact conditions derived from a direct linearization of the standard jump conditions. For a straightforward comparison between both approaches, all conditions are written in terms of a curvilinear coordinate system attached to the interface. The normal Lagrangian displacement continuity across the interface is proved to be a sufficient condition. The jump conditions for mass, momentum, energy and entropy are discussed, yielding conditions for the Lagrangian perturbations of displacement, stress, heat flux and temperature. Displacement and stress jump conditions are shown to coincide with literature results. The mixed Eulerian-Lagrangian description is likely to be advantageous over its fully Eulerian or Lagrangian counterparts. It yields an interesting unification between existing formulations for inviscid fluids (Galbrun's equation) and solids (updated Lagrangian formulation), together with simpler jump conditions.

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Section: Myers Approach For Eulerian Perturbationsmentioning

confidence: 99%

Jump conditions for unsteady small perturbations at fluid–solid interfaces in the presence of initial flow and prestress

Treyssède¹,

Tahar²

2009

Wave Motion

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“…To obtain the acoustic equations for the inlet, first the flow potential $ is rewritten as the sum of a steady axisymmetric mean flow potential 4>(r,z) and an acoustic potential <f> *=^ + (^(r,z)e-/(w '-me) (3) To account for spinning modes, the acoustic potential in equation (3) has been modified to include e""*. Also the solutions have been assumed to be harmonic (e~""') in time.…”

Section: Fig 5 Theoretical Far Field Spl Directionality Pattern For mentioning

confidence: 99%

“…References [1] and [2] contain a literature review of the techniques, advantages, and limitations associated with the various numerical solutions of the sound propagation equations in ducts. The purpose of the present paper is to investigate how accurately a newly developed hybrid finite element-integral program [3] simulates the measured noise radiated from the JT15D inlet.…”

Section: Introductionmentioning

confidence: 99%

Finite Element-Integral Acoustic Simulation of JT15D Turbofan Engine

Baumeister

Horowitz

1984

Journal of Vibration and Acoustics

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An .iterative finite element-integral technique is used to predict the sound field radlatedfrom the JTl5D turbofan inlet. The soundfield is divided into two regions: the sound field within and near the inlet which is computed using the finite element method, and the radiation field beyond the inlet which is calculated using an integral solution technique. The velocity potential formulation of the acoustic wave equation was employed in the program. For some single mode JTJ5D datil, the theory and experiment are in good agreement for the far field radiation pattern as well as suppressor attenuation. Also, the computer program is used to simulate flight effects that cannot be performed on a ground static test stand.

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“…While this is not the subject of the present paper, it should be pointed out that a conventional statement of the acoustic field equations [4] would require as data the external flow velocities and velocity derivatives at several points within each acoustic finite element. This in itself creates a large computational problem and requires huge data files for input to the acoustic computational scheme.…”

Section: Introductionmentioning

confidence: 98%

“…This in itself creates a large computational problem and requires huge data files for input to the acoustic computational scheme. It has been routine in the industry to use what amount to boundary element methods [4,5] for the steady flow calculations. These methods are not directly compatible with the finite element acoustic calculations.…”

Section: Introductionmentioning

confidence: 99%

Contributions to the Finite Element Solution of the Fan Noise Radiation Problem

Eversman

Parrett

Preisser

et al. 1985

Journal of Vibration and Acoustics

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The radiation of fan generated noise to the far field from a nacelle of realistic geometry is investigated using the finite element method. Several innovations have been introduced to minimize the computational requirements and create a highly efficient numerical scheme. The innovations include: (1) formulation of the problem in terms of velocity potential and density in such a way that no inlet mean flow velocity derivatives are required in the field equations, (2) the use of "wave envelope" elements in an outer region permitting a grid much coarser than would be used for conventional finite elements, (3) the use of a mesh which deforms with an increase of forward flight speed so that mesh lines are always lines of constant phase and rays for a point source, permitting the use of wave envelope elements and simple boundary conditions for any case of forward velocity, (4) an efficient scheme for introducing the noise source via modal amplitude coefficients, and (5) the use of a frontal solution technique which for physically realistic problems drastically reduces the active storage requirements. The finite element scheme is outlined, as are the specific details of the innovations. Results are given for cases where comparable experimental data are available.

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An iterative finite element-integral technique for predicting sound radiation from turbofan inlets in steady flight

Cited by 17 publications

References 11 publications

Jump conditions for unsteady small perturbations at fluid–solid interfaces in the presence of initial flow and prestress

Jump conditions for unsteady small perturbations at fluid–solid interfaces in the presence of initial flow and prestress

Finite Element-Integral Acoustic Simulation of JT15D Turbofan Engine

Contributions to the Finite Element Solution of the Fan Noise Radiation Problem

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