Optical measurements in evolving dispersed pipe flows

Voulgaropoulos, Victor; Angeli, Panagiota

doi:10.1007/s00348-017-2445-4

Cited by 29 publications

(19 citation statements)

References 46 publications

(47 reference statements)

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“…with the experimental results of Vlachogiannis et al 47 and Hou et al 44 . Any discrepancies between the current work and Hou et al 44 recorded close to the pipe wall could be attributed to the PIV uncertainties, which are more susceptible to near-wall measurement errors, as has also been discussed elsewhere 30,[53][54][55] . The discrepancies in the results concerning k X between Hou et al 44 and the present measurements shown in Fig.…”

Section: Underlying Relationshipsmentioning

confidence: 50%

On the link between experimentally‐measured turbulence quantities and polymer‐induced drag reduction in pipe flows

et al. 2019

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In this study, we investigate the hydrodynamics of polymer-induced drag reduction in horizontal turbulent pipe flows. We provide spatiotemporally resolved information of velocity and its gradients obtained with particle image velocimetry (PIV) measurements in solutions of water with dissolved polyethylene oxide (PEO) of three different molecular weights, at various dilute concentrations and with flow Reynolds numbers from 35, 000 to 210, 000. We find that the local magnitudes of important turbulent flow variables correlate with the measured levels of drag reduction irrespective of the flow Reynolds number, polymer weight and concentration. Contour maps illustrate the spatial characteristics of this correlation. A relationship between the drag reduction and the turbulent flow variables is found. The effects of the polymer molecular weight, its concentration and the Reynolds number on the flow are further examined through joint probability distributions of the fluctuations of the streamwise and spanwise velocity components.

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Section: Underlying Relationshipsmentioning

confidence: 50%

On the link between experimentally‐measured turbulence quantities and polymer‐induced drag reduction in pipe flows

et al. 2019

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“…Optical diagnostics allow for real-time, in situ imaging of one-(1-D), two-(2-D) or three-dimensional (3-D) spatial distributions of seeded or naturally occurring tracermolecules or particles, and are therefore often preferred to more "conventional" approaches, including instrumentation such as thermocouples, and conductivity and capacitance probe measurements. Fluorescence-based techniques, in particular, have been employed in a wide range of multiphase flows for the identification of interfaces [15,16], the investigation of gas and liquid entrainment [17,18], the identification of mixing zones [19][20][21][22], and the measurement of temperature [13,23] and velocity [24,25]. Planar laser-induced fluorescence (PLIF), which we currently employ in order to recover the film-height, relies on the (planar) illumination of a section of the flow, and the subsequent collection of the fluorescence emitted by the dye-seeded liquid over the excitation plane.…”

Section: Measurement Techniquesmentioning

confidence: 99%

Spatiotemporally resolved heat transfer measurements in falling liquid-films by simultaneous application of planar laser-induced fluorescence (PLIF), particle tracking velocimetry (PTV) and infrared (IR) thermography

Charogiannis

Markides

2019

Experimental Thermal and Fluid Science

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We present an optical technique that combines simultaneous planar laser-induced fluorescence (PLIF), particle tracking velocimetry (PTV) and infrared (IR) thermography for the space-and time-resolved measurement of the film-height, 2-D velocity and 2-D free-surface temperature in liquid films falling over an inclined, resistively-heated glass substrate. Using this information and knowledge of the wall temperature, local and instantaneous heat-transfer coefficients (HTCs) and Nusselt numbers, Nu, are also recovered along the waves of liquid films with Kapitza number, Ka = 180, and Prandtl number, Pr = 77. By employing this technique, falling-film flows are investigated with Reynolds numbers in the range Re = 18 − 66, wave frequencies set to f w = 7, 12 and 17 Hz, and a wall heat flux set toq = 2.5 W cm −2. Complementary data are also collected in equivalent (i.e., for the same mean-flow Re) flows withq = 0 W cm −2. Quality assurance experiments are performed that reveal deviations of up to 2-3% between PLIF/PTV-derived film heights, interfacial/bulk velocities and flow rates, and both analytical predictions and direct measurements of flat films over a range of conditions, while IR-based temperature measurements fall within 1 • C of thermocouple measurements. Highly localized film height, velocity, flow-rate and interface-temperature data are generated along the examined wave topologies by phase/wave locked averaging. The application of a heat flux (q = 2.5 W cm −2) results in a pronounced "thinning" of the investigated films (by 18%, on average), while the mean bulk velocities compensate by increasing by a similar extent to conserve the imposed flow rate. The axial-velocity profiles that are obtained in the heated cases are parabolic but "fuller" compared to equivalent isothermal flows, excluding any wave-regions where the interface slopes are high. As the Re is reduced, the heating applied at the wall penetrates through the film, resulting in a pronounced coupling between the HTC and the film height in thinner film regions. When the imposed wave frequency is increased, a narrower range of HTCs is observed, which we link to the evolution of the film topology and the associated redistribution of the fluid flow upstream of the imaging location, as the liquid viscosity decreases. The local and instantaneous Nu is strongly coupled to the film height and experiences variations that increase as f w is reduced.

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“…For instance, several authors have estimated the mixing performances for several mixer geometries by injecting polymers, by injecting dye fluids, by performing CFD simulations, or by using Laser Induced Fluorescence technique in the static mixers (Pahl and Muschelknautz 1982;Rauline et al 1998;Lemenand et al 2003;Meijer et al 2012;Das et al 2013;Ghanem et al 2014;Montante et al 2016). Other authors investigated the static mixers using the PIV mainly in single phase or liquid-liquid flows in recent years (Voulgaropoulos and Angeli 2017;Alekseev et al 2017). To the best of our knowledge, the high frequency PIV has never been employed in gas-liquid flows in previous works.…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamics of gas-liquid dispersion in transparent Sulzer static mixers SMXTM

Scala

Gamet

Malbec

et al. 2020

Chemical Engineering Science

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Optical measurements in evolving dispersed pipe flows

Cited by 29 publications

References 46 publications

On the link between experimentally‐measured turbulence quantities and polymer‐induced drag reduction in pipe flows

On the link between experimentally‐measured turbulence quantities and polymer‐induced drag reduction in pipe flows

Spatiotemporally resolved heat transfer measurements in falling liquid-films by simultaneous application of planar laser-induced fluorescence (PLIF), particle tracking velocimetry (PTV) and infrared (IR) thermography

Hydrodynamics of gas-liquid dispersion in transparent Sulzer static mixers SMXTM

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