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Research Papers: Flows in Complex Systems

Noise Filtering for Wall-Pressure Fluctuations in Measurements Around a Cylinder With Laminar and Turbulent Flow Separation

[+] Author and Article Information
C. Sardu

Dipartimento di Ingegneria
Meccanica e Aerospaziale,
Politecnico di Torino,
Corso Duca degli Abruzzi 24,
Torino 10129, Italy
e-mail: costantino.sardu@polito.it

D. Lasagna

Engineering and Environment,
University of Southampton,
Southampton SO17 1BJ, UK
e-mail: davide.lasagna@soton.ac.uk

G. Iuso

Dipartimento di Ingegneria
Meccanica e Aerospaziale,
Politecnico di Torino,
Corso Duca degli Abruzzi 24,
Torino 10129, Italy
e-mail: gaetano.iuso@polito.it

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received July 28, 2015; final manuscript received November 15, 2015; published online January 8, 2016. Assoc. Editor: Alfredo Soldati.

J. Fluids Eng 138(6), 061101 (Jan 08, 2016) (12 pages) Paper No: FE-15-1519; doi: 10.1115/1.4032034 History: Received July 28, 2015; Revised November 15, 2015

This paper proposes two different noise cancellation techniques for cleaning wall-pressure fluctuations signals. These fluctuations are measured around a circular cylinder with laminar and turbulent flow separation. The noise cancellation techniques are based on Wiener and adaptive filters and use the signals of pressure transducers mounted in a cross section of the cylinder and the signal of a free-field sensor opportunely located upstream. First, synthetic signals are used in order to validate the procedure. Then, both techniques are applied to the experimental data. Specific attention is paid to the filter order, optimized by a method introduced in this paper. Both filter types showed a selective behavior preserving the essence of the fluid dynamic phenomena characterizing the flow fields at each Reynolds number tested, especially when laminar separation occurs.

Copyright © 2016 by ASME
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Figures

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Fig. 1

Calibration devices: (a) loudspeaker and (b) end plate for the pressure transducers positioning

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Fig. 2

Spectra before (a) and after (b) the calibration

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Fig. 3

Comparison of the time histories of Mic1 and B&K before (a) and after the calibration (b)

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Fig. 4

Cylinder in the test section and the location of the reference microphone

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Fig. 5

Noise cancellation filter concept for Wiener and adaptive filters

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Fig. 6

Algorithm for the definition of the filter order

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Fig. 7

Short time history of synthetic signal contaminated with random noise (a) and cleaned with Wiener filter (b)

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Fig. 8

Comparison of filters (Wiener and adaptive) using synthetic signal

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Fig. 9

Results of noise cancellation in case of loudspeaker signal contamination. Wiener and adaptive filters.

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Fig. 10

Validation test with loudspeaker. Wiener noise cancellation for Mic1 (θ = 15 deg).

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Fig. 11

Validation test with loudspeaker. Zoom around 180 Hz, the frequency of the loud speaker disturbance. Mic1 (θ = 15 deg).

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Fig. 12

Validation test with loudspeaker: comparison of techniques. Mic1 (θ = 15 deg).

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Fig. 13

Validation test with loudspeaker. Comparison of techniques, zoom around 180 Hz, the frequency of the loud speaker disturbance. Mic1 (θ = 15 deg).

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Fig. 14

Results of Wiener and adaptive filters for the noise cancellation for laminar flow separation

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Fig. 15

Wiener noise cancellation applied to laminar separation case: (a) Mic1 (θ = 15 deg) and (b) Mic7 (θ = 120 deg)

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Fig. 16

Blades disturbances applied to laminar separation case. Wiener noise cancellation for Mic1 (θ = 15 deg).

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Fig. 17

Comparison of noise cancellation techniques applied to laminar separation case: (a) Mic1 (θ = 15 deg) and (b) Mic7 (θ = 120 deg)

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Fig. 18

Results of Wiener and adaptive filters for the noise cancellation in turbulent flow separation

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Fig. 19

Wiener noise cancellation applied turbulent flow separation Mic1 (θ = 15 deg attached flow)

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Fig. 20

Blades disturbance removal Wiener noise cancellation-turbulent flow separation Mic1 (θ = 15 deg)

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