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Research Papers: Flows in Complex Systems

Unsteady Vortex Flows Produced by Trailing Edge Articulation

[+] Author and Article Information
Stephen A. Huyer, David Beal

 Naval Undersea Warfare Center, Newport, RI 02841

Daniel Macumber, Anuradha Annaswamy

 Massachusetts Institute of Technology, Cambridge, MA 02139-4307

J. Fluids Eng 130(3), 031105 (Mar 11, 2008) (7 pages) doi:10.1115/1.2844579 History: Received February 09, 2007; Revised January 03, 2008; Published March 11, 2008

The unsteady vortex flows produced by biologically inspired tail articulation are investigated. The application is to provide active means of reducing tonal noise due to upstream wake interaction with downstream propellers on underwater vehicles. By reducing the wake velocity defect, the periodic unsteady propeller blade pressure fluctuations that are the source of the noise should be reduced. Accordingly, experiments to measure the flows produced by an upstream stator fitted with a movable trailing edge were carried out in a water tunnel for Reynolds numbers in the range 75,000<Re<300,000. A stator model with a hinged flapping trailing edge section operated at frequencies up to 21Hz corresponding to a range of Strouhal number 0.0<St<0.18. Velocity measurements of the articulating stator wake were carried out by laser Doppler velocimetry (LDV) and particle image velocimetry (PIV). Reduced mean and rms LDV data show that trailing edge articulation generates vortex structures with dependence on both Strouhal number and articulation amplitude. Estimates of the time mean stator drag that were obtained by integrating the mean wake profiles were used to estimate optimal Strouhal numbers in terms of wake elimination. Instantaneous phase-averaged measurements via PIV show a transition in the unsteady stator wake flow regimes as St is increased, from a deflected vortex sheet to a series of rolled up, discrete vortices. Measurements of the wake highlight the characteristics of the vortex structures and provide a means to estimate the impact on downstream propellers.

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Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 7

Vertical velocity wake profiles for A=10deg, U0=2m∕s, and St=0.0, 0.016, 0.033, 0.065, 0.089, and 0.122.

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Figure 8

Total drag estimates derived from wake profile integration as a function of Strouhal number for articulation amplitudes of 5deg, 10deg, and 20deg

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Figure 9

Downstream vorticity plots derived from PIV data for A=10deg and St=0.033, 0.092, and 0.184. The line at x∕c=1.0 refers to the velocity measurement rake in later figures and the horizontal line plots the location of the TE

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Figure 10

Instantaneous axial velocity wake profiles taken one chord length downstream of the articulating TE highlighting the induced velocity due to the upper and lower vortices for St=0.017, 0.034, 0.046, 0.067, 0.092, and 0.184

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Figure 11

Instantaneous axial velocity wake profiles taken one chord length downstream of the articulating TE highlighting the induced velocity between the upper and lower vortices for St=0.017, 0.034, 0.046, 0.067, 0.092, and 0.184

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Figure 1

Research water tunnel and experimental setup

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Figure 2

Four bar linkage and stator with TE flap

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Figure 3

Base line axial velocity wake profiles for A=0deg, U0=1m∕s, 2m∕s, and 4m∕s, and St=0

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Figure 4

Axial velocity wake profiles for A=10deg, U0=1m∕s, 2m∕s, and 4m∕s, and St=0.064

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Figure 5

Axial velocity wake profiles for A=5deg, 10deg, and 20deg, U0=2m∕s, and St=0.064

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Figure 6

Axial velocity wake profiles for A=10deg, U0=2m∕s, and St=0.0, 0.016, 0.033, 0.065, 0.089, and 0.122

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