Department of Mechanical engineering

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Author: search.filters.author.Yadav, Shyam SunderSubject: search.filters.subject.Electrohydrodynamics

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    Influence of electric potential boundary condition on the electrospraying process
    (Elsevier, 2025-08) Rao, Venkatesh K.P.; Yadav, Shyam Sunder
    In the current work, we perform three dimensional numerical simulations of the electrospraying process. Our aim is to investigate the effect of electric potential boundary condition on the electrospraying process of a liquid. We observe a steady electrospraying process in the cone jet mode for the case of uniform electric potential boundary condition. On the other hand, we observe a highly unsteady, violent electrospraying process for the case of non-uniform boundary condition. We provide explanation of this widely different behavior of the electrospraying process.
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    Oscillations of a Sessile Droplet in Contact and Non-contact Modes Under an AC Electric Field
    (Springer, 2016-09) Yadav, Shyam Sunder
    In the present work we numerically investigate the oscillations of a sessile conducting droplet in the contact and non-contact modes under an alternating electric field. We show that the oscillations in the non-contact mode, where the needle electrode remains away from the drop, are caused by the electric forces due to charge accumulation at the apex of the drop. In the contact mode case, where the needle remains dipped inside the drop, the electric charge accumulates at the drop surface just above the dielectric coating with a maximum value near the three phase contact line. These charges push the three phase contact line outwards with an oscillatory force which leads to drop oscillations. We also observe that higher needle voltage (~1 kV) is required for the non-contact mode while considerably less potential (~10 V) is enough for the contact mode to cause drop oscillations.
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    Numerical simulations of bubble formation from a submerged orifice and a needle: The effects of an alternating electric field
    (Elsevier, 2016) Yadav, Shyam Sunder
    In many applications, such as bubble column reactors, electric field is employed to provide a greater control on the sizes of bubbles forming at orifices and needles. In this study, we investigate the effects of an alternating electric field on the bubble dynamics. We perform numerical simulations of an alternating electric field coupled with two-phase flow using a Coupled Level-Set and Volume-of-Fluid method. We show that bubbles forming at orifices and needles decrease in size (up to ) only for a range of applied frequency and for other frequencies, the size of bubbles can be much bigger compared to the bubbles forming in the corresponding DC electric field case. The oscillating electric forces excite capillary waves on the bubble interface resulting in applied frequency dependent bubble oscillations. The numerically observed resonance for the needle case corresponds to , where is the frequency of the oscillation of the electric field force at the interface and is the capillary time scale, indicating that the resonance behavior is indeed governed by the interactions between the capillary and electric field force. A decomposition of bubble profile shapes into Legendre modes shows that for orifice as well as the needle case, second mode is most dominant followed by the fourth mode.
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    Numerical investigation of a conducting drop’s interaction with a conducting liquid pool under an external electric field
    (Elsevier, 2020-06) Yadav, Shyam Sunder
    A charged conducting drop suspended in an insulating medium shows non-coalescence with an interface under high strength of an externally applied electric field. We perform numerical simulations of the non-coalescence phenomenon to understand the underlying physical mechanisms and the effect of electric field strength and fluid conductivity on the coalescence behavior of a conducting drop with a conducting liquid pool under highly viscous conditions. We show that two factors primarily govern the coalescence or non-coalescence of the drop with the interface. First, the magnitude of the charge transfer time scale (which governs the rate of charge transfer during contact between the drop and the pool) relative to the time scale of the capillary waves. Second, the strength of the electric forces compared to the viscous forces. We further show that for the case of macro drops ( mm), charge transfer by fluid convection dominates charge conduction at lower electric conductivities ( S/m) only. Finally, we explain the non-dependence of secondary droplet’s size and charge on the fluid’s electric conductivity as observed in the experiments.