Acoustic Doppler velocimetry measurements of flow over a backward-facing step

Araújo, Maria Amélia V.C.; Araújo, Billy Jácome de; Greenwood, Brian

doi:10.1080/00221686.2019.1671521

Cited by 3 publications

(1 citation statement)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The precision and sources of error of ADVs in the measurements of the mean and higher-order statistics of turbulent flows have been quantified. More precisely, it has been shown that ADVs predict mean and Reynolds shear stresses accurately; however, their precision in measuring normal Reynolds stresses and small-scale turbulence have been questioned (Nikora and Goring 1998;Voulgaris and Trowbridge 1998;Hurther and Lemmin 2008;Khorsandi et al 2012;Quaresma et al 2017;Huang et al 2018;Araujo et al 2019). The sources of noise are divided into different categories, including (i) sampling error related to resolving phase shifts, which is not flow related; (ii) Doppler noise, which is intrinsic to the technique and is mainly caused by turbulence and particle scattering in the sampling volume; and (iii) error due to the mean velocity shear in the sampling volume (Lohrmann et al 1994;Lhermitte and Lemmin 1994;Voulgaris and Trowbridge 1998;Hurther and Lemmin 2008;Li et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Effect of Acoustic Doppler Velocimeter Sampling Volume Size on Measurements of Turbulence

Kazemi

Khorsandi

Mydlarski

2021

Journal of Atmospheric and Oceanic Technology

View full text Add to dashboard Cite

The relatively large sampling volume of acoustic Doppler velocimeters (ADVs) is expected to influence their measurement of turbulence. To study this effect, a series of experiments using different sampling volume sizes was conducted in an axisymmetric turbulent jet. The results show that the mean velocities are not significantly affected by the size of the sampling volume. On the other hand, reducing the sampling volume size results in an increase in the variances of the u and v velocities, while its effect on the variance of the w-velocity is negligible. Application of a noise reduction method to the data renders the velocity variances nearly independent of sampling volume size, suggesting that the difference was mainly due to Doppler noise. The principal conclusion of this work is therefore that – as long as the characteristic length of sampling volume is much smaller than the integral length scale of flow – increasing the sampling volume size (i.e., increasing spatial averaging over highly correlated scatterers) can reduce Doppler noise and result in more accurate measurements of the velocity variances. Application of noise reduction methods to the data is found to be especially important when the sampling volume size is reduced to capture smaller scales, or for near-boundary measurements. Furthermore, noise due to mean velocity shear, even at the largest velocity gradient along the jet radial profile, is found to be negligible in the present work.

show abstract