A critical review on advanced velocity measurement techniques in pulsating flows

Nabavi, Majid; Siddiqui, Kamran

doi:10.1088/0957-0233/21/4/042002

Cited by 35 publications

(30 citation statements)

References 120 publications

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“…An overview of the advantages and limitations of these techniques is given by Nabavi and Siddiqui. 11 Planar (2D) PIV (Ref. 30) is chosen here because PIV provides quantitative evaluation of twodimensional velocity fields.…”

Section: B Measurement Techniquementioning

confidence: 99%

“…These contradictions motivate ongoing interest in pulsatile flow 9 and highlight the demand for more experimental data. 5,10,11 The earliest studies, which relied on pressure drop measurements, showed that the mean Reynolds number for which transition occurs decreased from Re ¼ 2200-2400 (for steady flow) to as low as 1500 when the pulsatile component is increased. 12 In vivo studies in dog aortas using hot film anemometry confirmed this behavior: both Nerem and Seed 13 and Falsetti et al 14 concluded that the critical Reynolds number decreases with increasing Womersley number (a).…”

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confidence: 99%

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An experimental study of transitional pulsatile pipe flow

et al. 2012

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The transitional regime of a sinusoidal pulsatile flow in a straight, rigid pipe is investigated using particle image velocimetry. The main aim is to investigate how the critical Reynolds number is affected by different pulsatile conditions, expressed as the Womersley number and the oscillatory Reynolds number. The transition occurs in the region of Re ¼ 2250-3000 and is characterized by an increasing number of isolated turbulence structures. Based on velocity fields and flow visualizations, these structures can be identified as puffs, similar to those observed in steady flow transition. Measurements at different Womersley numbers yield similar transition behavior, indicating that pulsatile effects do not play a role in the regime that is investigated. Variations of the oscillatory Reynolds number also appear to have little effect, so that the transition here seems to be determined only by the mean Reynolds number. For larger mean Reynolds numbers, a second regime is observed: here, the flow remains turbulent throughout the cycle. The turbulence intensity varies during the cycle, but has a phase shift with respect to the mean flow component. This is caused by a growth of kinetic energy during the decelerating part and a decay during the accelerating part of the cycle. Flow visualization experiments reveal that the flow develops localized turbulence at several random axial positions. The structures quickly grow to fill the entire pipe in the decelerating phase and (partially) decay during the accelerating phase.

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Section: B Measurement Techniquementioning

confidence: 99%

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confidence: 99%

An experimental study of transitional pulsatile pipe flow

et al. 2012

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“…The obtained results confirmed that averaging over 200 cycles has no effect on W. The scatter in the results increased slightly with increasing divergence angle, but remained less than 4% for W. However, in the hot-wire measurement, we cannot easily accurately determine the direction of the flow at a position and time when the ratio of the radial component to the axial component of the velocity is large. For such a case, a certain amount of error is unavoidable [19], particularly near the wall. Furthermore, we also verified that the flow properties were symmetric with respect to the diffuser axis.…”

Section: Measurement Proceduresmentioning

confidence: 99%

Experimental Investigation of Pulsating Turbulent Flow Through Diffusers

Sumida¹

2016

IJFMTS

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This paper presents the results of an experimental study on a pulsating turbulent flow through conical diffusers with total divergence angles (2θ) of 12°, 16°, and 24°, whose inlet and exit were connected to long straight pipes. To examine the effects of the divergence angle and the nondimensional frequency on flow characteristics, experiments were systematically conducted using a hot-wire anemometry and a pressure transducer. Moreover, the pressure rise between the inlet and the exit of the diffuser was analyzed approximately under the assumption of a quasi-steady flow and expressed in the form of simple empirical equations in terms of the time-mean value, the amplitude, and the phase difference from the flow rate variation. The expressions are in good agreement with the experimental results and very useful in practice. With the increase in the Womersley number, α, and 2θ, the sinusoidal change in the phase-averaged velocity, W, with time becomes distorted, and the W distributions show a more complicated behavior. For the flow at α=10 in the diffusers with large 2θ, the distributions of W are depressed on the diffuser axis. In contrast, for the flow at α=20, W has a protruding distribution on the diffuser axis.

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“…Most of them, such as the hot-wire anemometry, laser Doppler velocimetry and ultrasonic Doppler velocimetry, are point-based techniques [1,2]. Particle image velocimetry is an optical technique capable of measuring two-dimensional flow fields with high spatial resolution [3,4].…”

Section: Introductionmentioning

confidence: 99%