Rainbow refractrometry on particles with radial refractive index gradients

Saengkaew, Sawitree; Charinpanitkul, Tawatchai; Vanisri, Hathaichanok; Tanthapanichakoon, Wiwut; Biscos, Y.; Garcı́a, N.; Lavergne, G.; Méès, Loïc; Gouesbet, G.; Gréhan, Gérard

doi:10.1007/s00348-007-0342-y

Cited by 40 publications

(8 citation statements)

References 18 publications

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“…Evaporating droplets are characterized by the presence of a refractive index gradient inside the droplet (related to temperature gradient) and by the presence of a air/vapor mixture film all around it. The internal refractive index gradient can be considered in GLMT simulation by considering a large number of layers with a nearly continuous refractive index evolution [19]. GLMT simulations (not presented here) show that such an internal gradient does not affect the droplet holograms in the present configuration (at large distance) and will be not considered in the following.…”

Section: C Evaporating Droplet Hologramsmentioning

confidence: 99%

Evaporating droplet hologram simulation for digital in-line holography setup with divergent beam

et al. 2013

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Generalized Lorenz-Mie theory (GLMT) for a multilayered sphere is used to simulate holograms produced by evaporating spherical droplets with refractive index gradient in the surrounding air/vapor mixture. Simulated holograms provide a physical interpretation of experimental holograms produced by evaporating Diethyl Ether droplets with diameter in the order of 50 μm and recorded in a digital in-line holography configuration with a divergent beam. Refractive index gradients in the surrounding medium lead to a modification of the center part of the droplet holograms, where the first fringe is unusually bright. GLMT simulations reproduce this modification well, assuming an exponential decay of the refractive index from the droplet surface to infinity. The diverging beam effect is also considered. In both evaporating and nonevaporating cases, an equivalence is found between Gaussian beam and plane wave illuminations, simply based on a magnification ratio to be applied to the droplets' parameters.

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Section: C Evaporating Droplet Hologramsmentioning

confidence: 99%

Evaporating droplet hologram simulation for digital in-line holography setup with divergent beam

et al. 2013

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“…The refractive index values are of the order of 1.375 for the shortest distances, that is significantly greater than value generally admitted for liquid Diethyl Ether, which is about 1.35. This over-estimation is due to the presence of a refractive index gradient (temperature and/or composition gradient due to evaporation) inside the droplet as shown in Saengkaew et al (2007). At larger distances from the nozzle (between 11 and 15 mm), the measured refractive index decreases fast and not regularly.…”

Section: Evolution Of the Droplets Refractive Indexmeasurements At Ramentioning

confidence: 99%

Lagrangian measurements of the fast evaporation of falling diethyl ether droplets using in-line digital holography and a high-speed camera

et al. 2014

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measurements of the fast evaporation of falling diethyl ether droplets using in-line digital holography and a high-speed camera. Experiments in Fluids, Springer Verlag (Germany), 2014, 55, 1708 (13 p.). 10.1007/s00348-014-1708-6. ujm-01020697 Experiments in Fluids manuscript No. (will be inserted by the editor) Lagrangian measurements of the fast evaporation of falling Diethyl Ether droplets using in-line digital holography and a high-speed camera Abstract The evaporation of falling Diethyl Ether droplets is measured by following droplets along their trajectories. Measurements are performed at ambient temperature and pressure by using in-line digital holography. The holograms of droplets are recorded with a single high-speed camera and reconstructed with an "inverse problems" approach algorithm previously tested (Chareyron et al 2012). Once evaporation starts, the interfaces of the droplets are surrounded by air/vapor mixtures with refractive index gradients that modify the holograms. The central part of the droplets holograms is unusually bright compared to what is expected and observed for non-evaporating droplets. The reconstruction process is accordingly adapted to measure the droplets diameter along their trajectory. The Diethyl Ether being volatile, the droplets are found to evaporate in a very short time: of the order of 70 ms for a 50 − 60 µm diameter at an ambient temperature of 25• C. After this time, the Diethyl Ether has fully evaporated and droplets diameter reaches a plateau. The remaining droplets are then only composed of water, originating from the cooling and condensation of the humid air at the droplet surface. This assertion is supported by two pieces of evidence: (i) by estimating the evolution of droplets refractive index from light scattering measurements at rainbow angle, and (ii) by

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“…Results showed a significant decrease in the accuracy of rainbow refractometry. Saengkaew et al (2007) studied the sensitivity of the SRR to a radial gradient of refractive index and demonstrated that it is always possible to find an equivalent particle with a homogeneous refractive index which scatters light in both forward and backward directions in the same way as a particle with a gradient. However, the temperature corresponding to the refractive index of this equivalent particle is rather difficult to interpret physically.…”

Section: Standard Rainbow Refractometry (Srr)mentioning

confidence: 99%

“…The inversion consists of looking for the best correlation in the Fourier domain (position of the characteristic frequencies and phases) between experimental light scattered profiles and refined calculations based on an exact method like LMT which also take the optical devices' field of view into account (Han et al 1998;Min and Gomez 1996). Saengkaew et al (2007) employed this kind of inversion method on a monodisperse stream of ethanol droplets (initial diameter around 95 lm) slowly evaporating in air at ambient temperature. They claimed to have observed a size variation of 0.2 lm over 2 cm and an associated temperature variation of 5°C.…”

Section: Standard Rainbow Refractometry (Srr)mentioning

confidence: 99%

Temperature and chemical composition of droplets by optical measurement techniques: a state-of-the-art review

Lemoine

Castanet

2013

Exp Fluids

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Rainbow refractrometry on particles with radial refractive index gradients

Cited by 40 publications

References 18 publications

Evaporating droplet hologram simulation for digital in-line holography setup with divergent beam

Evaporating droplet hologram simulation for digital in-line holography setup with divergent beam

Lagrangian measurements of the fast evaporation of falling diethyl ether droplets using in-line digital holography and a high-speed camera

Temperature and chemical composition of droplets by optical measurement techniques: a state-of-the-art review

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