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Research Papers

Zonal Large-Eddy Simulation of a Fan Tip-Clearance Flow, With Evidence of Vortex Wandering

[+] Author and Article Information
Jérôme Boudet

LMFA, UMR CNRS 5509,
Ecole Centrale de Lyon,
Université de Lyon,
Ecully Cedex 69134, France
e-mail: jerome.boudet@ec-lyon.fr

Adrien Cahuzac

LMFA, UMR CNRS 5509,
Ecole Centrale de Lyon,
Université de Lyon,
Ecully Cedex 69134, France

Philip Kausche

Abteilung Triebwerksakustik,
Institut für Antriebstechnik,
Deutsches Zentrum für Luft-und
Raumfahrt (DLR),
Berlin 10623, Germany

Marc C. Jacob

LMFA, UMR CNRS 5509,
Université Lyon 1,
Université de Lyon,
Ecully Cedex 69134, France

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received October 22, 2013; final manuscript received September 22, 2014; published online November 25, 2014. Assoc. Editor: Graham Pullan.

J. Turbomach 137(6), 061001 (Jun 01, 2015) (9 pages) Paper No: TURBO-13-1240; doi: 10.1115/1.4028668 History: Received October 22, 2013; Revised September 22, 2014; Online November 25, 2014

The flow in a fan test-rig is studied with combined experimental and numerical methods, with a focus on the tip-leakage flow. A zonal RANS/LES approach is introduced for the simulation: the region of interest at tip is computed with full large-eddy simulation (LES), while Reynolds-averaged Navier–Stokes (RANS) is used at inner radii. Detailed comparisons with the experiment show that the simulation gives a good description of the flow. In the region of interest at tip, a remarkable prediction of the velocity spectrum is achieved, over about six decades of energy. The simulation precisely captures both the tonal and broadband contents. Furthermore, a detailed analysis of the simulation allows identifying a tip-leakage vortex (TLV) wandering, whose influence onto the spectrum is also observed in the experiment. This phenomenon might be due to excitation by upstream turbulence from the casing boundary layer and/or the adjacent TLV. It may be a precursor of rotating instability. Finally, considering the outlet duct acoustic spectrum, the vortex wandering appears to be a major contribution to noise radiation.

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References

Figures

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Fig. 1

Sketch of the DLR fan rig

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Fig. 2

DLR fan rig with the hot-wire traverses (marked with white ovals)

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Fig. 3

Hot-wire probes inside the fan rig duct

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Fig. 4

Overall performance of the fan. Δ: reduced fan loading (ψ), ○: efficiency (η). The filled symbols represent the operating condition of the present study (Ω = 3195 rpm), while the hollow symbols are for a lower shaft speed (Ω = 3000 rpm).

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Fig. 11

Turbulence intensity of the fluctuations downstream of the rotor (computed in the rotating frame of reference). (a) contours (the simulation domain boundaries are drawn on the experimental map). (b) radial profiles (time and azimuthal average). ×: measurements; solid line: simulation.

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Fig. 12

Power spectral density of the axial velocity, in the downstream plane at radius r=0.98 Rc. Dashed line: experiment; solid line: simulation.

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Fig. 13

Power spectral density of the tangential velocity, in the downstream plane at radius r=0.98 Rc. Dashed line: experiment; solid line: simulation.

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Fig. 14

Simulation: power spectral density of the axial velocity, at a point attached to the rotating frame of reference, in the downstream plane at radius r = 0.98 Rc

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Fig. 15

Experiment: sound pressure spectrum

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Fig. 16

Real part of the radial velocity Fourier transform (f = 1800 Hz): isosurfaces at –4 × 10−6 m/s (dark gray) and 4 × 10−6 m/s (light gray)

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Fig. 10

Mean velocity components downstream of the rotor (computed in the rotating frame of reference). (a), (c), and (e): contours (the simulation domain boundaries are drawn on the experimental maps). (b), (d), and (f): radial profiles (time and azimuthal average). ×: measurements; solid line: simulation.

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Fig. 9

Radial profile (time and azimuthal average) of axial velocity Ux in the fan face plane. ×: measurements; solid line: simulation.

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Fig. 8

Instantaneous isosurface of Q-criterion (8 × 107s–2), colored by chordwise vorticity

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Fig. 7

Mean pressure coefficient on the blade surface, from the simulation. Solid line: midspan; dashed-dotted line: close to the tip at 97% span.

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Fig. 6

Streamlines of the LES mean flow in the blade tip region

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Fig. 5

Computational domain: inlet duct sector and rotor passage. The mesh on a meridian sheet is shown, with every second point plotted in each direction.

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