We present a robust and computationally efficient numerical scheme for simulating steady electrohydrodynamic atomization processes (electrospray). The main simplification assumed in this is that all the free electrical charges are distributed over interface. A comparison of results with those calculated volume-of-fluid method showed presented here accurately describes flow pattern within entire liquid domain. Experiments were performed to partially validate predictions. simulations...

It has been documented since the Renaissance that an air bubble rising in water will deviate from its straight, steady path to perform a periodic zigzag or spiral motion once is above critical size. Yet, unsteady rise resisted quantitative description, and physical mechanism remains dispute. Using numerical mapping technique, we for first time find agreement with high-precision measurements of instability. Our linear stability analysis shows straight becomes unstable perturbation (a Hopf...

The liquid cone-jet mode can be produced upon stimulation by a coflowing gas sheath. Most applications deal with the jet breakup, leading to either of two droplet generation regimes: Jetting and dripping. flow pattern is explored direct axisymmetric volume fluid (VOF) numerical simulation; its evolution studied as rate increased around jetting-dripping transition. As observed in other focused flows such electrospraying cones steady thread emission, displays strong recirculating within...

We study numerically the nonlinear stationary states of a droplet covered with an insoluble surfactant in uniaxial extensional flow. calculate both eigenfunctions to reveal instability mechanism and time-dependent resulting from it, which provides coherent picture phenomenon. The transition is saddle-node type, without surfactant. flow becomes unstable under linear perturbations. Surfactant considerably reduces interval stable capillary numbers. Inertia increases deformation decreases...

In the flow focusing technique, a liquid rate Q is injected through microcapillary to form meniscus attached its edge. The stretched until thin jet tapers from tip due action of gas stream driven by pressure drop Δp. Both and cross orifice plate located in front capillary at distance H. present work, stability both tapering emitted analyzed experimentally. Three regimes are identified: (i) steady jetting regime, where stable convectively unstable; (ii) local instability absolutely (iii)...

We examine both theoretically and experimentally the breakup of a pendant drop loaded with an insoluble surfactant. The experiments show that significant amount surfactant is trapped in resulting satellite droplet. This result contradicts previous theoretical predictions, where effects surface tension variation were limited to solutocapillarity Marangoni stresses. solve numerically hydrodynamic equations, including not only those but also shear dilatational viscosities. viscosities play...

The breakup of low-viscosity droplets like water is a ubiquitous and rich phenomenon. Theory predicts that in the inviscid limit one observes finite-time singularity, giving rise to universal power law, with prefactor for given density surface tension. This universality has been proposed as powerful tool determine dynamic tension at short time scales. We combine high-resolution experiments simulations show this unobservable practice: contrast previous studies, we fluid system parameters do...

We study both numerically and experimentally the steady cone-jet mode of electrospraying close to stability limit minimum flow rate. The leaky dielectric model is solved for arbitrary values relative permittivity electrohydrodynamic Reynolds number. linear analysis base flows conducted by calculating their global eigenmodes. rate determined as that which growth factor dominant becomes positive. find a good agreement between this theoretical prediction experimental values. spatial structure...

We examine the behaviour of a compound capillary jet from spatio-temporal linear stability analysis Navier–Stokes equations. map jetting–dripping transition in parameter space by calculating Weber numbers for which convective/absolute instability occurs. If remaining dimensionless parameters are set, there two critical that verify Brigg's pinch criterion. The region absolute (convective) corresponds to smaller (larger) than highest value those numbers. is affected significantly presence...

The global stability of the steady jetting mode liquid jets focused by coaxial gas streams is analyzed both theoretically and experimentally. Numerical simulations allow one to identify physical mechanisms responsible for instability in low viscosity very viscous regimes liquid. characteristic flow rates which takes place are estimated a simple scaling analysis. These do not depend on pressure drop (energy) applied system produce microjet. Their dependencies opposite two extremes studied:...

The electrohydrodynamic response of low-conductivity pendant drops to a step change in the electric field magnitude was examined both numerically and experimentally. Both leaky-dielectric perfect-conductor models were solved simulations. Experiments conducted precisely measure drop interface shape as function time. oscillated for applied voltages smaller than critical value which depended on rest governing parameters. It stretched subsequently emitted microjet from its tip potentials above...

The physics of electrospray has been subject to an intense debate for three decades regarding the ultimate electrokinetics that determines electric current and size emitted droplets in steady Taylor cone-jet mode (TCJ). In order solve with a high degree accuracy complete electrokinetic structure TCJ, this work, we have used full Poisson–Nernst–Planck model equations, which solved using numerical scheme. We consider formulation no interfacial adsorption ions, as Mori & Young ( J. Fluid...

We study numerically the microjetting mode obtained when a fluid is injected through tube submerged in uniaxial extensional flow. The steady solution to full nonlinear Navier–Stokes equations calculated. obtain linear global modes determining stability of solution. For sufficiently large outer viscosity, flow remains stable for infinitely small values rate. This implies that jets with vanishing diameters can be produced regardless jet viscosity and strength. inner-to-outer ratio, instability...

In this experimental and numerical study, we revisit the question of onset elastic regime in viscoelastic pinch-off. This is relevant to all modern filament thinning techniques, which aim measure extensional properties low-viscosity polymer solutions. Examples are slow retraction method (SRM) for capillary breakup rheometry (CaBER), or dripping method, a drop detaches from nozzle. As part these stable liquid bridge brought slowly its stability threshold, where capillary-driven starts. slows...

Recent experimental studies on the instability of capillary jets have revealed suitability a linear spatiotemporal analysis to ascertain parametrical conditions for specific flow regimes such as steady jetting or dripping. In this work, an extensive analytical, numerical, and description confined is provided, leading integrated picture both in terms data interpretation. We propose extended, accurate analytic model low Reynolds number limit, introduce numerical scheme predict system response...