Scalar concentration measurements in liquid-phase flows with pulsed lasers

Shan, Jerry W.; Lang, Daniel B.; Dimotakis, Paul E.

doi:10.1007/s00348-004-0817-z

Cited by 12 publications

(13 citation statements)

References 17 publications

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“…These levels of laser irradiance are significantly higher than the saturation intensity I sat of most fluorescent dyes (Crimaldi 2008). Values of I sat have been estimated or inferred for rhodamine 6G (Shan et al 2004) and rhodamine WT (Melton and Lipp 2003) to be of order 1 MW/cm 2 . When pulsed lasers are used to induce the fluorescence, it is thus common to have partially saturated fluorescence.…”

Section: Introductionmentioning

confidence: 99%

The saturation of the fluorescence and its consequences for laser-induced fluorescence thermometry in liquid flows

et al. 2016

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Section: Introductionmentioning

confidence: 99%

The saturation of the fluorescence and its consequences for laser-induced fluorescence thermometry in liquid flows

et al. 2016

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“…Using these background and reference images, the effects of CCD sensitivity variation, illumination non-uniformity, and optical transfer function were removed using (3). The imaged jet-fluid concentration was referenced to the jet-plenum dye concentration, c 0 , † The low concentrations used in the jet experiment, and near-saturation of fluorescence, caused absorption to be a small fraction of the initial laser intensity, I L,0 (Shan et al 2004). It was verified in fluorescence measurements of a uniform-concentration field that laser attenuation due to absorption was small for the mean-concentration-pathlength of the jet images.…”

Section: Imaging Techniquementioning

confidence: 99%

Reynolds-number effects and anisotropy in transverse-jet mixing

Shan

Dimotakis

2006

J. Fluid Mech.

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Experiments are described which measured concentration fields in liquid-phase strong transverse jets over the Reynolds-number range 1.0 × 10 3 6 Re j 6 20 × 10 3 . Laserinduced-fluorescence measurements were made of the jet-fluid-concentration fields at a jet-to-freestream velocity ratio of V r = 10. The concentration-field data for far-field (x/d j = 50) slices of the jet show that turbulent mixing in the transverse jet is Reynoldsnumber dependent over the range investigated, with a scalar-field PDF that evolves with Reynolds number. A growing peak in the PDF, indicating enhanced spatial homogenization of the jet-fluid concentration field, is found with increasing Reynolds number. Comparisons between transverse jets and jets discharging into quiescent reservoirs show that the transverse jet is an efficient mixer in that it entrains more fluid than the ordinary jet, yet is able to effectively mix and homogenize the additional entrained fluid. Analysis of the structure of the scalar field using distributions of scalar increments shows evidence for well-mixed plateaux separated by sharp cliffs in the jet-fluid concentration field, as previously shown in other flows. Furthermore, the scalar field is found to be anisotropic, even at small length scales. Evidence for local anisotropy is seen in the scalar power spectra, scalar microscales, and PDFs of scalar increments in different directions. The scalar-field anisotropy is shown to be correlated to the vortex-induced large-scale strain field of the transverse jet. These experiments add to the existing evidence that the large and small scales of high-Schmidt-number turbulent mixing flows can be linked, with attendant consequences for the universality of small scales of the scalar field for Reynolds numbers up to at least Re = 20 × 10 4 .

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“…Here, the pulse duration is practically unaltered, but the energy of the pulse is redistributed into a broader optical bandwidth at higher wavelengths. This technique has proven to be very effective and was already applied in shadowgraph experiments (Zijlstra and Ohl 2008) and is closely related to fluorescent flow visualization described in Rau et al (2006) and Shan et al (2004). A disadvantage is that the cuvette containing the dye can act as a secondary laser cavity (Schäfer et al 1966), thereby partially restoring the coherent nature of the pulse (see Fig.…”

Section: Introductionmentioning

confidence: 99%

iLIF: illumination by Laser-Induced Fluorescence for single flash imaging on a nanoseconds timescale

et al. 2011

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The challenge in visualizing fast microscale fluid motion phenomena is to record high-quality images free of motion-blur. Here, we present an illumination technique based on laser-induced fluorescence which delivers high-intensity light pulses of 7 ns. The light source consists of a Q-switched Nd:YAG laser and a laser dye solution incorporated into a total internal reflection lens, resulting in a uni-directional light beam with a millimetersized circular aperture and 3°divergence. The laser coherence, considered undesirable for imaging purposes, is reduced while maintaining a nanoseconds pulse duration. The properties of the illumination by laser-induced fluorescence (iLIF) are quantified, and a comparison is made with other high-intensity pulsed and continuous light sources.

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Scalar concentration measurements in liquid-phase flows with pulsed lasers

Cited by 12 publications

References 17 publications

The saturation of the fluorescence and its consequences for laser-induced fluorescence thermometry in liquid flows

The saturation of the fluorescence and its consequences for laser-induced fluorescence thermometry in liquid flows

Reynolds-number effects and anisotropy in transverse-jet mixing

iLIF: illumination by Laser-Induced Fluorescence for single flash imaging on a nanoseconds timescale

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