Velocity measurements on highly turbulent free surface flow using ADV

Cea, Luís; Puertas, Jerónimo; Pena, Luis

doi:10.1007/s00348-006-0237-3

Cited by 140 publications

(86 citation statements)

References 18 publications

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“…The de-spiking filters of Goring and Nikora (2002) (phase-space thresholding method modified by Wahl (2002) which is used in the SONTEK data analysis software, WinADV) and Cea et al (2007) were tested on the current jet data. However, they did not reduce the RMS velocities significantly as the signal quality was high in the present laboratory flow.…”

Section: Post-processing and Noise-reduction Methodsmentioning

confidence: 99%

“…It has been found that the ADV accurately predicts the mean velocity and the Reynolds shear stresses in bed shear dominated turbulence (e.g., in rivers) (Voulgaris and Trowbridge, 1998;Hurther and Lemmin, 2008). However its accuracy in measuring turbulence quantities such as the normal components of the Reynolds stresses, turbulent kinetic energy, and the turbulent microscales has been questioned (Nikora and Goring, 1998;Voulgaris and Trowbridge, 1998;Cea et al, 2007;Hurther and Lemmin, 2008). Voulgaris and Trowbridge (1998) Therefore, the effect of noise is more significant on the horizontal RMS velocities than on the vertical RMS velocity and the Reynolds shear stresses.…”

Section: Acoustic Doppler Velocimetrymentioning

confidence: 99%

“…Hurther and Lemmin (2001) ADVs. These include the phase-space thresholding method of Goring and Nikora (2002) and the despiking filters of Cea et al (2007). In addition, Nikora and Goring (1998) presented a post-processing filter that removed Doppler noise from the ADV's measured velocities.…”

Section: Acoustic Doppler Velocimetrymentioning

confidence: 99%

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Effect of background turbulence on an axisymmetric turbulent jet

2013

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The effect of background turbulence on a turbulent jet was investigated experimentally. The primary objective of this work was to study the effect of different levels of the background turbulence on the dynamics and mixing of an axisymmetric turbulent jet at different Reynolds numbers. The secondary objective, which arose during the experiments, was to improve the acoustic Doppler velocimetry measurements which were found to be inaccurate when measuring turbulence statistics.In addition to acoustic Doppler velocimetry (ADV), flying hot-film anemometry was employed in this study. To move the hot-film probe at constant speeds, a high precision traversing mechanism was designed and built. A data acquisition system and LabVIEW programs were also developed to acquire data and control the traversing mechanism. The experiments started by benchmarking the two measurement techniques in an axisymmetric turbulent jet. Comparing the results with those of the other studies validated the use of flying hot-film anemometry to estimate the mean and the root-mean square (RMS) velocities.The experiments also validated the use of ADV for measurement of the mean velocities (measured in three Cartesian directions) and the RMS velocity (measured in the z-direction only). RMS velocities measured by the ADV along the x-and y-direction of the probe were overestimated.Attempts to improve the turbulence statistics measured by the ADV using the post-processing and noise-reduction methods presented in the literature were undertaken. However, the RMS velocities remained higher than the accepted values. In addition, a noise-reduction method was presented in this study which reduced the RMS velocities down to the accepted values. It was also attempted to relate Doppler noise to current velocity, and thus improve the results by iv subtracting the Doppler noise from the measured RMS velocities in the jet. However, no relationship was found between the Doppler noise and the mean velocity.The effect of different levels of background turbulence on the dynamics and mixing of an axisymmetric turbulent jet at different Reynolds numbers was then investigated. The background turbulence was generated by a random jet array. To confirm that the turbulence is approximately homogeneous and isotropic and has a low mean flow, the background flow was first characterized. Velocity measurements in an axisymmetric jet issuing into two different levels of background turbulence were then conducted. Three different jet Reynolds

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Section: Post-processing and Noise-reduction Methodsmentioning

confidence: 99%

Section: Acoustic Doppler Velocimetrymentioning

confidence: 99%

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Effect of background turbulence on an axisymmetric turbulent jet

2013

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“…Goring and Nikora (2002) is probably the most popular paper that provides the details of despiking the ADV data where several despiking algorithms are available. Later, some of other algorithms have been developed by Cea et al (2007), Parsheh et al (2010), Wright andBaas (2013), andMacVicar et al (2014) etc.…”

Section: Introductionmentioning

confidence: 99%

Measurement of turbulent flow in a narrow open channel

Sarkar

2016

Journal of Hydrology and Hydromechanics

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Abstract:The paper presents the experimental results of turbulent flow over hydraulically smooth and rough beds. Experiments were conducted in a rectangular flume under the aspect ratio b/h = 2 (b = width of the channel 0.5 m, and h = flow depth 0.25 m) for both the bed conditions. For the hydraulically rough bed, the roughness was created by using 3/8″ commercially available angular crushed stone chips; whereas sand of a median diameter d 50 = 1.9 mm was used as the bed material for hydraulically smooth bed. The three-dimensional velocity components were captured by using a Vectrino (an acoustic Doppler velocimeter). The study focuses mainly on the turbulent characteristics within the dip that were observed towards the sidewall (corner) of the channel where the maximum velocity occurs below the free-surface. It was also observed that the nondimensional Reynolds shear stress changes its sign from positive to negative within the dip. The quadrant plots for the turbulent bursting shows that the signs of all the bursting events change within the dip. Below the dip, the probability of the occurrence of sweeps and ejections are more than that of inward and outward interactions. On the other hand, within the dip, the probability of the occurrence of the outward and inward interactions is more than that of sweeps and ejections.

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“…Goring and Nikora (2002) assumed that good data can be found within a cluster and that points located outside the cluster are spikes. They suggested a method based on iterative phase-space thresholding as the most suitable solution for spike detection, and this technique is now frequently used (Cea et al 2007). Spike data may simply be removed from the time series.…”

Section: Methodsmentioning

confidence: 99%

Improving the accuracy of four‐receiver acoustic Doppler velocimeter (ADV) measurements in turbulent boundary layer flows

Doroudian

Bagherimiyab

Lemmin

2010

Limnology & Ocean Methods

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Acoustic Doppler instrument measurements suffer from random spikes and Doppler noise. Using a fourreceiver ADV (acoustic Doppler velocimeter; Vectrino manufactured by Nortek) that allows recording beam velocities, we combine a spike-removal procedure on the beam velocities with a noise-reduction method on the flow velocities to improve turbulence measurements. We compare the results with those obtained from ADVP (acoustic Doppler velocity profiler) measurements under the same conditions, i.e., in turbulent open-channel flow over a coarse-grained bed. It is shown that spikes are best removed from ADV beam velocity data before calculating flow velocities, thereby correcting all three flow velocity components at the source. Spikes in beam velocities do not correlate with low correlation values. ADVP data generally have few spikes and do not need spike removal treatment, showing that spikes are instrument related. The noise reduction method is based on the decorrelation of the Doppler noise terms contained in two vertical velocities redundantly sampled in the same volume. The combined ADV data treatment is sufficient to significantly extend the resolved frequency range in the velocity spectra. It reduces RMS values by up to a factor of 2, and the corrected values agree with ADVP results and theoretical predictions, indicating that both treatments are needed. Owing to spatial averaging effects over the ADV sample volume, a sampling frequency limit of close to 50 Hz is determined by the deviation of the spectra from the -5/3 slope.

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Velocity measurements on highly turbulent free surface flow using ADV

Cited by 140 publications

References 18 publications

Effect of background turbulence on an axisymmetric turbulent jet

Effect of background turbulence on an axisymmetric turbulent jet

Measurement of turbulent flow in a narrow open channel

Improving the accuracy of four‐receiver acoustic Doppler velocimeter (ADV) measurements in turbulent boundary layer flows

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