New methodology to subtract noise effects from turbulence parameters computed from ADV velocity signals

GARCÍA, C.M.; CANTERO, M.I.; REHMANN, C.; GARCÍA M.H.

Salt Lake City, Utah, USA.

Congreso; World Water and Environmental Resources Congress 2004; 2004

American Society of Civil Engineers (ASCE)

The Acoustic Doppler Velocimeter (ADV) signals are affected by Doppler noise which isintrinsic to the Doppler measurement technique. It has the characteristics of white noiseand its integral effects must be subtracted from some turbulence parameters. New toolsare introduced in this paper to evaluate the relative importance of the noise energy on thetotal energy as well as to define the characteristic frequency in the measured energyspectrum where noise energy is more important than turbulent energy (flat plateau). Todevelop these tools a model for the power spectrum is adopted which allows the analysisof a range of flow conditions. Results show that noise energy can have an importantcontribution on the total measured energy, mainly in low energy flows. However in thosecases, the noise energy level can be defined from the spectrum because the characteristicfrequency is smaller than the Nyquist frequency. After the noise energy level is defined,corrections to the rest of the turbulent parameters (length and time scale, convectivevelocity, etc) must be performed.