Digital in-line holography to quantify secondary droplets from the impact of a single drop on a thin film

Guildenbecher, Daniel Robert; Engvall, Luke; Gao, Jian; Grasser, Thomas W.; Reu, Phillip L.; Chen, Jun

doi:10.1007/s00348-014-1670-3

Cited by 42 publications

(21 citation statements)

References 23 publications

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“…In spite of its significance, the size distribution of airborne droplets resulting from raindrop impact on a deep pool has not been reported before, although Blanchard & Woodcock (1957) make some semi-quantitative estimates for raindrops falling near terminal velocity. Droplets impacting on a dry surface or on a thin liquid film have produced log-normal (Levin & Hobbs 1971;Stow & Stainer 1977;Guildenbecher et al 2014) or exponential distributions (Xu, Barcos & Nagel 2007). Droplet size distributions have also been measured for phenomena that bear some topological similarity to the present conditions, in particular the presence of a sheet with a thickened rim and protruding ligaments (Clanet 2007).…”

Section: Airborne Droplet Statisticsmentioning

confidence: 98%

Splash behaviour and oily marine aerosol production by raindrops impacting oil slicks

Murphy

d’Albignac

et al. 2015

J. Fluid Mech.

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The high-speed impact of a droplet on a bulk fluid at high Weber number (We) is not well understood but is relevant to the production of marine aerosol by raindrop impact on the sea surface. These splashes produce a subsurface cavity and a crown which closes into a bubble canopy, but a floating layer of immiscible oil, such as a crude oil slick, alters the splash dynamics. The effects of oil layer fluid properties and thickness, droplet size and impact speed are examined by high-speed visualization. Oil layer rupture and crown behaviour are classified by dimensional scaling. The subsurface cavity volume for impact on thick layers is shown to depend on the Reynolds number (Re), although canopy formation at high Re introduces a competing We effect since rapid canopy closure is found to retard cavity expansion. Time-resolved kinematic measurements show that thin crude oil slicks similarly alter crown closure and cavity growth. The size and spatial distributions of airborne droplets are examined using high-speed holographic microscopy. The droplets have a bimodal distribution with peaks at 50 and 225 µm and are clustered by size at different elevation angles. Small droplets (50 µm) are ejected primarily at shallow angles, indicating production by splashing within the first 100 µs and by breakup of microligaments. Larger droplets (225 µm) are found at steeper elevation angles, indicating later production by capillary instability acting on large ligaments protruding upward from the crown. Intermittent droplet release while the ligaments grow and sweep upward is thought to contribute to the size-dependent spatial ordering. Greater numbers of small droplets are produced at high elevation angles when a crude oil layer is present, indicating satellite droplet formation from ligament breakup. A crude oil layer also increases the target fluid Ohnesorge number, leading to creation of an intact ejecta sheet, which then ruptures to form aerosolized oil droplets.

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Section: Airborne Droplet Statisticsmentioning

confidence: 98%

Splash behaviour and oily marine aerosol production by raindrops impacting oil slicks

Murphy

d’Albignac

et al. 2015

J. Fluid Mech.

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“…Gao and co-workers [9,10] developed a DH-based system to characterize single drop breakup both in the aerodynamic flow field and from the impact on a film. Yang and co-workers [11,12] applied DH to the spray fields measurement.…”

Section: Introductionmentioning

confidence: 99%

Characterization of atomization and breakup of acoustically levitated drops with digital holography

Yao

et al. 2014

Appl. Opt.

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A digital holographic particle tracking velocimetry system is applied to quantitatively study the drop atomization induced by capillary waves, and the breakup caused by increased sound pressure levels. A wavelet-based algorithm is used for particle detection and autofocusing with a wide size range of 20 μm-2 mm. To eliminate the influence of large particles on small particles, a two-step detection method is adopted. Large drops are first characterized and simulated by a diffraction-based model. Then the contributions of the drops are subtracted from the original hologram followed by the detection of small droplets. Finally, the velocity and size distribution of the secondary droplets are obtained from the experimental holograms. The results demonstrate the validity of the digital in-line holographic technique for the atomization and breakup study of acoustically levitated drops.

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“…Advantages of the hybrid method include automatic selection of segmentation thresholds, applicability to arbitrary-shaped particles, and demonstrated accuracy. A detailed description of the hybrid method can be found in [15], and applications are available in [9,10].…”

Section: A Hybrid Methodsmentioning

confidence: 99%

“…Furthermore, 3D trajectories and velocities can be extracted from sequential holograms via particle matching. The literature contains many applications to solid particles [1][2][3][4], liquid or gaseous particles [5][6][7][8][9][10], and biological particles [11,12], where particle sizes range from a few to hundreds of micrometers. Note, in order to resolve small particles [9] or to expand the field of view (FOV) [13], magnification is usually introduced by a lens added in the optical path.…”

Section: Introductionmentioning

confidence: 99%

Refinement of particle detection by the hybrid method in digital in-line holography

et al. 2014

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Digital in-line holography provides simultaneous particle size and three-dimensional position measurements. In general, the measurement accuracy varies locally, and tends to decrease where particles are closely spaced, due to noise resulting from diffraction by adjacent particles. Aggravating the situation is the identification of transversely adjoining particles as a single particle, which introduces significant errors in both size and position measurements. Here, we develop a refinement procedure that distinguishes such erroneous particles from accurately detected ones and further separates individual particles. Effectiveness of the refinement is characterized using simulations, experimental holograms of calibration fields, and a few practical applications to liquid breakup. Significant improvements in the accuracy of the measured particle sizes, positions, and displacements confirm the usefulness of the proposed method.

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Digital in-line holography to quantify secondary droplets from the impact of a single drop on a thin film

Cited by 42 publications

References 23 publications

Splash behaviour and oily marine aerosol production by raindrops impacting oil slicks

Splash behaviour and oily marine aerosol production by raindrops impacting oil slicks

Characterization of atomization and breakup of acoustically levitated drops with digital holography

Refinement of particle detection by the hybrid method in digital in-line holography

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