Vortex-ring-induced elliptical drop deformation process in ambient liquid under an impact: The effects of the drop shape and other parameters

Abstract This paper presents an experimental study of impact of water drop on a surface in a spreading regime with no splashing. Three surfaces were studied: virgin glass, coating film and woven cotton fabric at different construction parameters. All experiments were carried out using water drop with the same free fall high. Digidrop with high-resolution camera is used to measure the different parameters characterising this phenomenon. Results show an important effect of the height of the free fall on the drop profile and the spreading behaviour. An important drop deformation at the surface impact was observed. Then, fabric construction as the weft count deeply affects the drop impact. For plain weave, an increase of weft count causes a decrease in penetration and increase in the spreading rate. The same result was obtained for coated fabric. Therefore, the impact energy was modified and the drop shape was affected, which directly influenced the spreading rate.

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Drop deformation and emulsion rheology under the combined influence of uniform electric field and linear flow

Journal of Fluid Mechanics ◽

10.1017/jfm.2017.897 ◽

2018 ◽

Vol 841 ◽

pp. 408-433 ◽

Cited By ~ 12

Author(s):

Shubhadeep Mandal ◽

Sudipta Sinha ◽

Aditya Bandopadhyay ◽

Suman Chakraborty

Keyword(s):

Electric Field ◽

Strain Rate ◽

Relative Strength ◽

Extensional Viscosity ◽

Uniform Electric Field ◽

Drop Deformation ◽

Perturbation Approach ◽

Electrohydrodynamic Flow ◽

Linear Flow ◽

Drop Shape

Electrohydrodynamics of a leaky dielectric suspended drop subjected to the combined influence of a uniform electric field and linear velocity field is analysed analytically and numerically. In the limit of small charge convection and small shape deformation, an analytical solution is obtained for the deformed drop shape when the imposed linear flow is of uniaxial extensional type with the extensional component aligned in the direction of the electric field. This perturbation approach is then applied towards obtaining the effect of a uniform electric field on the effective extensional rheology of a dilute emulsion. Key results indicate that the magnitude and sense of drop deformation not only depends on the material properties of the drop and medium but is also governed by the strength of the applied electric field relative to the applied flow field. The interfacial charge convection is found to increase or decrease the drop deformation depending on the direction of electrohydrodynamic flow and relative strength of electric field. The electrohydrodynamic flow and drop deformation modulates the effective extensional viscosity of the emulsion. Importantly, the presence of the electric field leads to strain-rate-dependent effective extensional viscosity of the emulsion. The emulsion is found to exhibit strain-rate thinning/thickening behaviour depending on the drop to medium charge relaxation time scale. The analytically obtained drop shape and deformation are in excellent agreement with numerical simulations for the small deformation ranges.

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Effect of Drop Deformation on Heat Transfer to a Drop Suspended in an Electrical Field

Journal of Heat Transfer ◽

10.1115/1.2824337 ◽

1998 ◽

Vol 120 (3) ◽

pp. 682-689 ◽

Cited By ~ 15

Author(s):

M. A. Hader ◽

M. A. Jog

Keyword(s):

Nusselt Number ◽

Steady State ◽

Heat Transport ◽

Peclet Number ◽

Drop Deformation ◽

Dielectric Fluid ◽

Electrical Field ◽

Drop Shape ◽

Péclet Number ◽

Internal Problem

Heat transfer to a drop of a dielectric fluid suspended in another dielectric fluid in the presence of an electric field is investigated. We have analyzed the effect of drop deformation on the heat transport to the drop. The deformed drop shape is assumed to be a spheroid and is prescribed in terms of the ratio of drop major and minor diameter. Results are obtained for both prolate and oblate shapes with a range of diameter ratio b/a from 2.0 to 0.5. The internal problem where the bulk of the resistance to the heat transport is in the drop, as well as the external problem where the bulk of the resistance is in the continuous phase, are considered. The electrical field and the induced stresses are obtained analytically. The resulting flow field and the temperature distribution are determined numerically. Results indicate that the drop shape significantly affects the flow field and the heat transport to the drop. For the external problem, the steady-state Nusselt number increases with Peclet number for all drop deformations. For a fixed Peclet number, the Nusselt number increases with decreasing b/a. A simple correlation is proposed to evaluate the effect of drop deformation on the steady-state Nusselt number. For the internal problem, for all drop deformations, the maximum steady-state Nusselt number becomes independent of the Peclet number at high Peclet number. The maximum steady-state Nusselt numbers for an oblate drop are significantly higher than that for a prolate drop.

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