Micro molecular tagging velocimetry for analysis of gas flows in mini and micro systems

Samouda, F.; Colin, Stéphane; Barrot-Lattes, Christine; Baldas, Lucien; Brandner, Juergen J.

doi:10.1007/s00542-013-1971-0

Cited by 15 publications

(20 citation statements)

References 42 publications

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“…However, in the recent MTV experimental studies of gaseous flows in a millimetric rectangular channel [44,57], the velocity profile, when it is simply deduced from an homothety of the streamwise displacement profile, appears to be more flatten than the expected theoretical velocity profile and an artificial velocity slip is observed at the wall. Samouda et al suggested that the effects of spanwise molecular diffusion could explain this behavior [44]. Actually, the tracer molecules appear to become displaced at the wall through advection in the MTV method, even when there is no velocity slip at the wall.…”

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confidence: 91%

“…After emission of a photon, the molecule comes back to its initial state and is then re-usable for a possible new laser excitation. Typically, a single laser beam is required to tag tracer molecules along a line [44] or on a grid [45]. The molecules luminescence is then detected at two successive times and the analysis of the tagged line displacement or of the grid deformation allows the determination of the velocity field.…”

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confidence: 99%

“…On the other hand, the first attempts to measure gas flows velocities by MTV inside devices with millimetric or sub-millimetric dimensions are quite recent and the techniques were based on MTV by direct phosphorescence using acetone as tracer molecule [44,55,56] or on MTV by photoproduct fluorescence using nitric oxide as tracer molecule [57]. These few preliminary measurements have been made in rectangular channels using one dimensional molecular tagging velocimetry (1D-MTV); in this case a single line or a series of parallel lines are tagged perpendicularly to the flow direction ( Fig.…”

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confidence: 99%

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Molecular tagging velocimetry by direct phosphorescence in gas microflows: Correction of Taylor dispersion

Mohand

Frezzotti

Brandner

et al. 2017

Experimental Thermal and Fluid Science

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Molecular tagging velocimetry is a little-intrusive technique based on the properties of specific molecules able to emit luminescence once properly excited. Several variants of this technique have been successfully developed for analyzing external gas flows or internal gas flows in large systems. There is, however, very few experimental data on molecular tagging velocimetry for gas flows in mini or microsystems, and these data are strongly affected by the molecular diffusion of the tracer molecules. In the present paper, it is demonstrated that the velocity field in gas microflows cannot be directly deduced from the measured displacement field without taking into account Taylor dispersion effects. For that purpose, the benchmark case of a Poiseuille gas flow through a rectangular channel 960 µm in depth is experimentally investigated by micro molecular tagging velocimetry using acetone vapor as a molecular tracer. An appropriate reconstruction method based on the advection diffusion equation is used to process the data and to correctly extract the velocity profiles. The comparison of measured velocities with flowrate data and with theoretical velocity profiles shows a good agreement, whereas when the reconstruction method is not implemented, the extracted velocity field exhibits qualitative and quantitative anomalies, such as a non-physical slip at the walls. The robustness of the reconstruction method is demonstrated on flows with light and heavy molecular species, namely helium and argon, at atmospheric as well as at 2 lower pressure conditions, for which diffusion effects are stronger. The obtained results represent an encouraging step for future analysis of rarefied gas microflows.

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confidence: 91%

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confidence: 99%

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confidence: 99%

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Molecular tagging velocimetry by direct phosphorescence in gas microflows: Correction of Taylor dispersion

Mohand

Frezzotti

Brandner

et al. 2017

Experimental Thermal and Fluid Science

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“…As shown by previous MTV applications to channel microflows in the hydrodynamic regime (Samouda et al 2015), the technique allows measuring gas velocity profiles with an uncertainty of the order of a few percent, which is comparable with accuracies obtained with usual velocimetry techniques.…”

Section: Discussionmentioning

confidence: 51%

“…However, even at atmospheric pressure, data processing of preliminary velocity profiles has shown several issues (Samouda et al 2015). The tagged molecules are subject to significant molecular diffusion and the diffusion effects should be taken into account during the data processing.…”

Section: Introductionmentioning

confidence: 99%

Role of diffusion on molecular tagging velocimetry technique for rarefied gas flow analysis

Frezzotti

Mohand

Barrot-Lattes

et al. 2015

Microfluid Nanofluid

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The molecular tagging velocimetry (MTV) is a well-suited technique for velocity field measurement in gas flows. Typically, a line is tagged by a laser beam within the gas flow seeded with light emitting acetone molecules. Positions of the luminescent molecules are then observed at successive times and the velocity field is deduced from the analysis of the tagged line displacement and deformation. However, the displacement evolution is expected to be affected by molecular diffusion, when the gas is rarefied. Therefore, there is no direct and simple relationship between the velocity field and the measured displacement of the initial tagged line. This paper addresses the study of tracer molecules diffusion through a background gas flowing in a channel delimited by planar walls. Tracer and background species are supposed to be governed by a system of coupled Boltzmann equations, numerically solved by the direct simulation Monte Carlo (DSMC) method. Simulations confirm that the diffusion of tracer species becomes significant as the degree of rarefaction of the gas flow increases. It is shown that a simple advection–diffusion equation provides an accurate description of tracer molecules behavior, in spite of the non-equilibrium state of the background gas. A simple reconstruction algorithm based on the advection–diffusion equation has been developed to obtain the velocity profile from the displacement field. This reconstruction algorithm has been numerically tested on DSMC generated data. Results help estimating an upper bound on the flow rarefaction degree, above which MTV measurements might become problematic

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Molecular tagging velocimetry of NH fluorescence in a high-enthalpy rarefied gas flow

Zhang

Yan

et al. 2017

Appl. Phys. B

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Micro molecular tagging velocimetry for analysis of gas flows in mini and micro systems

Cited by 15 publications

References 42 publications

Molecular tagging velocimetry by direct phosphorescence in gas microflows: Correction of Taylor dispersion

Molecular tagging velocimetry by direct phosphorescence in gas microflows: Correction of Taylor dispersion

Role of diffusion on molecular tagging velocimetry technique for rarefied gas flow analysis

Molecular tagging velocimetry of NH fluorescence in a high-enthalpy rarefied gas flow

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