Evaluation of a Triple-Axis Coherent Doppler Velocity Profiler for Measuring Near-Bed Flow: A Field Study

K. F. E. Betteridge Proudman Oceanographic Laboratory, Liverpool, United Kingdom

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P. S. Bell Proudman Oceanographic Laboratory, Liverpool, United Kingdom

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P. D. Thorne Proudman Oceanographic Laboratory, Liverpool, United Kingdom

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J. J. Williams Proudman Oceanographic Laboratory, Liverpool, United Kingdom

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Abstract

Collocated detailed measurements of near-bed turbulent and intrawave flow are important for studying sediment transport processes and seabed evolution. Existing commercially available triple-axis profiling instruments do not provide collocated velocity measurements. To improve the capability to make such measurements a triple-axis coherent Doppler velocity profiler (CDVP) has been developed and tested in the marine environment. The instrument was designed to measure orthogonal velocity profiles within a narrow column of water at 16 Hz within 1 m of the bed with a vertical spatial resolution of 0.05 m. This paper describes the first deployment of the instrument, in a tidal inlet in Portugal during a multidisciplinary study, when CDVP flow velocity measurements were compared with data from other instrumentation. A pragmatic approach was adopted to assess the capability of the triple-axis CDVP, using both an evaluation of internal consistency and an assessment against two commercially available acoustic Doppler velocimeters (ADVs). Measurements of the mean and fluctuating velocity profiles were collected with the triple-axis CDVP, and these have been shown to be internally consistent and to be in good agreement with measurements obtained with the ADVs.

Corresponding author address: K. F. E. Betteridge, Proudman Oceanographic Laboratory, 6 Brownlow St., Liverpool L3 5DA, United Kingdom. Email: kfeb@pol.ac.uk

Abstract

Collocated detailed measurements of near-bed turbulent and intrawave flow are important for studying sediment transport processes and seabed evolution. Existing commercially available triple-axis profiling instruments do not provide collocated velocity measurements. To improve the capability to make such measurements a triple-axis coherent Doppler velocity profiler (CDVP) has been developed and tested in the marine environment. The instrument was designed to measure orthogonal velocity profiles within a narrow column of water at 16 Hz within 1 m of the bed with a vertical spatial resolution of 0.05 m. This paper describes the first deployment of the instrument, in a tidal inlet in Portugal during a multidisciplinary study, when CDVP flow velocity measurements were compared with data from other instrumentation. A pragmatic approach was adopted to assess the capability of the triple-axis CDVP, using both an evaluation of internal consistency and an assessment against two commercially available acoustic Doppler velocimeters (ADVs). Measurements of the mean and fluctuating velocity profiles were collected with the triple-axis CDVP, and these have been shown to be internally consistent and to be in good agreement with measurements obtained with the ADVs.

Corresponding author address: K. F. E. Betteridge, Proudman Oceanographic Laboratory, 6 Brownlow St., Liverpool L3 5DA, United Kingdom. Email: kfeb@pol.ac.uk

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  • Betteridge, K. F. E., Thorne P. D. , and Bell P. S. , 2002: Assessment of acoustic coherent Doppler and cross-correlation techniques for measuring near-bed velocity and suspended sediment profiles in the marine environment. J. Atmos. Oceanic Technol., 19 , 367380.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hardcastle, P. J., 1994: A high resolution near-bed coherent acoustic Doppler current profiler for measurement of turbulent flow. Proc. Sixth Int. Conf. on Electronic Engineering in Oceanography, London, United Kingdom, IEE, Conf. Publ. 394, 73–76.

    • Crossref
    • Export Citation
  • Hurther, D., and Lemmin U. , 1998: A constant-beam-width transducer for 3D acoustic Doppler profile measurements in open-channel flows. Meas. Sci. Technol., 9 , 17061714.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hurther, D., and Lemmin U. , 2001: A correction method for turbulence measurements with a 3D acoustic Doppler velocity profiler. J. Atmos. Oceanic Technol., 18 , 446458.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lhermitte, R., and Serafin R. , 1984: Pulse-to-pulse coherent Doppler sonar signal processing techniques. J. Atmos. Oceanic Technol., 1 , 293308.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rolland, T., and Lemmin U. , 1997: A two-component acoustic velocity profiler for use in turbulent open-channel flow. J. Hydro. Res., 35 , 545562.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Thorne, P. D., and Taylor J. , 2000: Acoustic measurements of boundary layer flow and sediment flux. J. Acoust. Soc. Amer., 108 , 15681581.

  • Thorne, P. D., and Hanes D. , 2002: A review of acoustic measurement of small scale sediment processes. Cont. Shelf Res., 22 , 603632.

  • Veron, F., and Melville W. K. , 1999: Pulse-to-pulse coherent Doppler measurements of waves and turbulence. J. Atmos. Oceanic Technol., 16 , 15801596.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Voulgaris, G., and Trowbridge J. H. , 1998: Evaluation of the acoustic Doppler velocimeter (ADV) for turbulence measurements. J. Atmos. Oceanic Technol., 15 , 272289.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Williams, J. J., Bell P. S. , Humphery J. D. , Hardcastle P. J. , and Thorne P. D. , 2003a: New approach to measurement of sediment processes in a tidal inlet. Cont. Shelf Res., 23 , 12391254.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Williams, J. J., Bell P. S. , and Thorne P. D. , 2003b: Field measurements of flow fields and sediment transport above mobile bed forms. J. Geophys. Res., 108 , C4,. 636.

    • Search Google Scholar
    • Export Citation
  • Wilson, R. A., Thorne P. D. , Williams J. J. , Bell P. S. , and Hardcastle P. J. , 2000: An evaluation of a 3D acoustic coherent Doppler current profiler in the marine environment. Proc. of the Fifth European Conf. on Underwater Acoustics (ECUA 2000), Lyon, France, European Commission, 627–632.

  • Zedel, L., and Hay A. E. , 1999: A coherent Doppler profiler for high-resolution particle velocimetry in the ocean: Laboratory measurements of turbulence and particle flux. J. Atmos. Oceanic Technol., 16 , 11021117.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zedel, L., and Hay A. E. , 2002: A three component bistatic coherent Doppler velocity profiler: Error sensitivity and system accuracy. IEEE J. Ocean. Eng., 27 , 717725.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zedel, L., Hay A. E. , Cabrera R. , and Lohrmann A. , 1996: Performance of a single beam pulse to pulse coherent Doppler profiler. IEEE J. Ocean. Eng., 21 , 290297.

    • Crossref
    • Search Google Scholar
    • Export Citation
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