Shape and oscillations of the water drops freely suspended in a horizontal electric field: A wind tunnel study

Bhalwankar, Rohini; Deshpande, C. G.; Kamra, A. K.

doi:10.1016/j.jastp.2015.09.004

Cited by 5 publications

(16 citation statements)

References 40 publications

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“…Although, these changes are small, these are observed consistently for all drop sizes in both absence and presence of the electric field. Small decrease in oscillation frequency with drop diameter has been earlier observed by Szakáll et al [2010] and Bhalwankar et al [2015].…”

Section: Drop Breakup Chargingsupporting

confidence: 62%

“…Vertical velocity and the intensity of turbulence in the airflow in the cross section of the modified wind tunnel were measured with a precalibrated VelociCalc‐Multifunction ventilation meter (TSI model 9565‐P). It can measure the average velocity with a resolution of 0.01 m s −1 and calculates the intensity of turbulence from 3 min sample of the velocity reading in a particular position [ Bhalwankar et al ., ]. The depth of velocity well, i.e., the difference in velocity in the center of well with respect to the free‐stream velocity, in the modified wind tunnel reduced to ~12% as compared to that of ~30% in our earlier measurements [ Kamra et al ., ].…”

Section: Experimental Setup and Methodologymentioning

confidence: 99%

“…Water drops were suspended in a vertical air stream of an open-ended, low-turbulence vertical wind tunnel described by Kamra et al [1993]. In a minor modification of this wind tunnel, a wire mesh screen of size 8 meshes per centimeter was fixed between the blower and divergent section to streamline the incoming air [Bhalwankar et al, 2015]. A crossed-wire mesh screen of size 8 meshes per centimeter fixed below the test section of the wind tunnel slightly lowers the vertical air stream velocity in the center of the test section of the wind tunnel.…”

Section: Experimental Setup and Methodologymentioning

confidence: 99%

“…As discussed in our earlier study [ Bhalwankar et al ., ] the AVI (Audio Video Interleave) files recorded with high‐speed camera were manually cropped in such a way that the images of the oscillating drop remain within the cropped region. Images were analyzed by the “ImageJ,” a public domain Java image processing and analysis software to get major (2a) and minor (2b) axes of the drop from which axis ratios (b/a) were computed.…”

Section: Experimental Setup and Methodologymentioning

confidence: 99%

“…With a spatial pixel resolution of 24 µm, the error in the axis ratio measurement was estimated by assuming a 2 pixel uncertainty in the edge detection using an algorithm that converted gray scale images to binary version by ImageJ software. A relative error of ~4% is estimated for the axis ratios of the drop sizes considered in our measurements [ Bhalwankar et al ., ]. The oscillation frequency of drops was computed using fast Fourier transform analysis by converting the time series of drop axis ratio variations into the frequency domain.…”

Section: Experimental Setup and Methodologymentioning

confidence: 99%

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Breakup modes of the drops suspended in a vertical wind tunnel in presence of the horizontal electric field

2017

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The influence of strong horizontal electric field (EH) on different stages of deformation and eventual breakup of the large water drops of 6.6, 7.0, and 7.25 mm diameter has been observed in a vertical wind tunnel using high‐speed photography. Dumbbell, filament, and bag modes of drop breakup are observed when EH = 0. However, drops elongate in horizontal direction, mostly develop sharp curvature at their ends, eject a fine jet spray of tiny droplets, and ultimately break up into several droplets in EH = 500 kV m−1. Extreme elongation up to 29 mm is observed for a 7.0 mm diameter drop. Results show that the breakup time, i.e., the time from the drop's extreme prolate shape to its breakup in its final oscillation, ranges from 13 to 41 ms when EH = 0 and 57–105 ms when EH = 500 kV m−1. So although the lifetime of the drop since its suspension to breakup is reduced, its elongation and breakup time increase in EH. It suggests that the effect of EH in final oscillation before breakup overcomes the effect of hydrodynamic and aerodynamic forces in elongating the drop. Also, no breakup of bag type is observed in EH = 500 kV m−1. Moreover, the fragments formed after the drop breakup and tiny droplets ejected by their fragments carry electrical charges of polarity determined by the induced charge on the parent drop in EH. The significance of the results is discussed in modifying the drop growth and the radar echo‐precipitation relationships in thunderclouds.

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Section: Drop Breakup Chargingsupporting

confidence: 62%

Section: Experimental Setup and Methodologymentioning

confidence: 99%

Section: Experimental Setup and Methodologymentioning

confidence: 99%

Section: Experimental Setup and Methodologymentioning

confidence: 99%

Section: Experimental Setup and Methodologymentioning

confidence: 99%

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Breakup modes of the drops suspended in a vertical wind tunnel in presence of the horizontal electric field

2017

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Binary Collisions of water drops in presence of horizontal electric fields: A wind tunnel study

Bhalwankar

Pawar²,

Kamra

2022

Preprint

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Coalescence/breakup characteristics of binary collisions of small water drops (d S =0.4-1.8 mm diameter) with large drops (d L =3-3.5 mm diameter) occurring in the absence/presence of horizontal electric field (E H ) = 0, 100, and 300 kVm -1 have been investigated in a small vertical wind tunnel using a high-speed digital camera. The coalescence efficiency (E C ) of 0.299 observed for average diameters (d L =3.2 mm, d S =1.2 mm) in E H = 0 decreased to 0.244/0.211 when E H is increased to 100/300 kVm -1 . The increase in the electric field reduces the probability of coalescence when Weber number (We) <1. However, when We [?] 1, an increase in We restricts the probability of coalescence. Our data, when plotted in the regime diagram in the We*p plane, delineates the collision outcomes in all-electric field values but does show the overlapping of some data points in the adjacent categories. After a binary collision, the relaxation time required for the occurrence of coalescence is higher than that for the breakup. Further, the relaxation time increases from the filament to sheet to disk mode of breakup in all-electric field values. Fragment size distributions after the filament and sheet types of breakups differ and are differently affected by the applied electric field. Higher collision kinetic energy (CKE) has a tendency to increase the number of fragments of the sizes between d L and d S . It is concluded therefore that, the effect of the electric field needs to be included in the estimation of drop growth and precipitation in clouds.

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Experimental study on the falling and coalescence characteristics of droplets under alternating electric fields

Sun

Yang

Sun

et al. 2020

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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Shape and oscillations of the water drops freely suspended in a horizontal electric field: A wind tunnel study

Cited by 5 publications

References 40 publications

Breakup modes of the drops suspended in a vertical wind tunnel in presence of the horizontal electric field

Breakup modes of the drops suspended in a vertical wind tunnel in presence of the horizontal electric field

Binary Collisions of water drops in presence of horizontal electric fields: A wind tunnel study

Experimental study on the falling and coalescence characteristics of droplets under alternating electric fields

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