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Research Papers

Advanced Numerical Methods for the Prediction of Tonal Noise in Turbomachinery—Part II: Time-Linearized Methods

[+] Author and Article Information
Christian Frey

e-mail: Christian.Frey@dlr.de

Graham Ashcroft

e-mail: Graham.Ashcroft@dlr.de

Hans-Peter Kersken

e-mail: Hans-Peter.Kersken@dlr.de
Institute of Propulsion Technology,
German Aerospace Center (DLR),
Linder Höhe,
Cologne 51147, Germany

Christian Weckmüller

Institute of Propulsion Technology,
German Aerospace Center (DLR),
Müller-Breslaustr. 8,
Berlin 10623, Germany
e-mail: Christian.Weckmueller@dlr.de

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the Journal of Turbomachinery. Manuscript received August 2, 2012; final manuscript received April 26, 2013; published online September 26, 2013. Editor: David Wisler.

J. Turbomach 136(2), 021003 (Sep 26, 2013) (10 pages) Paper No: TURBO-12-1163; doi: 10.1115/1.4024649 History: Received August 02, 2012; Revised April 26, 2013

This is the second part of a series of two papers on unsteady computational fluid dynamics (CFD) methods for the numerical simulation of aerodynamic noise generation and propagation. It focuses on the application of linearized RANS methods to turbomachinery noise problems. The convective and viscous fluxes of an existing URANS solver are linearized and the resulting unsteady linear equations are transferred into the frequency domain, thereby simplifying the solution problem from unsteady time-integration to a complex linear system. The linear system is solved using a parallel, preconditioned general minimized residual (GMRES) method with restarts. In order to prescribe disturbances due to rotor stator interaction, a so-called gust boundary condition is implemented. Using this inhomogeneous boundary condition, one can compute the generation of the acoustic modes and their near field propagation. The application of the time-linearized methods to a modern high-bypass ratio fan is investigated. The tonal fan noise predicted by the time-linearized solver is compared to numerical results presented in the first part and to measurements.

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References

Figures

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Fig. 1

Prescribed acoustic wave in duct segment

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Fig. 2

Numerical dissipation error against grid resolution

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Fig. 3

Mach number distribution of mean flow through the DLR Rig 250 stator row

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Fig. 4

Real part of harmonic pressure on pressure (solid) and suction (dashed) side

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Fig. 5

Imaginary part of harmonic pressure on pressure (solid) and suction (dashed) side

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Fig. 6

Real part of harmonic pressure on pressure (solid) and suction (dashed) side. Perturbation amplitude has been increased by a factor of 4.

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Fig. 7

Imaginary part of harmonic pressure on pressure (solid) and suction (dashed) side. Perturbation amplitude has been increased by a factor of 4.

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Fig. 8

Real part of harmonic pressure on pressure (solid) and suction (dashed) side. Unsteady turbulence model versus constant eddy viscosity model.

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Fig. 9

Imaginary part of harmonic pressure on pressure (solid) and suction (dashed) side. Unsteady turbulence model versus constant eddy viscosity model.

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Fig. 10

Real part of harmonic pressure on pressure (solid) and suction (dashed) side. Two-dimensional nonreflecting boundary conditions are employed at outlets.

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Fig. 11

Imaginary part of harmonic pressure on pressure (solid) and suction (dashed) side. Two-dimensional nonreflecting boundary conditions are employed at outlets.

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Fig. 12

Model of the DLR–UHBR fan for the numerical simulations

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Fig. 13

Real part of second harmonic of axial velocity in the stator row. Time-linearized versus unsteady simulation.

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Fig. 14

Real part of second harmonic of blade surface pressure on suction side

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Fig. 15

Imaginary part of second harmonic of blade surface pressure on suction side

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Fig. 16

Real part of second harmonic of blade surface pressure on pressure side

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Fig. 17

Imaginary part of second harmonic of blade surface pressure on pressure side

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Fig. 18

Real part of harmonic surface pressure on stator caused by wave reflected at rotor blade row

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Fig. 19

Imaginary part of harmonic surface pressure on stator caused by wave reflected at rotor blade row

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Fig. 20

Real part of harmonic surface pressure on stator. Unsteady versus time-linearized solution using unsteady average.

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Fig. 21

Imaginary part of harmonic surface pressure on stator. Unsteady versus time-linearized solution using unsteady average.

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Fig. 22

Real part of the second harmonic of the pressure along the duct section

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Fig. 23

Sound pressure level of upstream acoustic mode of azimuthal order m = 6 and radial order n = 0, 1, 2. Time-linearized versus unsteady results and measurements.

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