Capillary electrohydrostatics of conducting drops hanging from a nozzle in an electric field

Journal Article · Wed Dec 01 00:00:00 EST 1993 · Journal of Colloid and Interface Science; (United States)

DOI:https://doi.org/10.1006/jcis.1993.1482· OSTI ID:5579445

Harris, M T; Basaran, O A ^[1]

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1. Oak Ridge National Lab., TN (United States)

A hybrid boundary element/finite element method is used to determine the axisymmetric equilibrium shapes and stability of a conducting drop hanging from a nozzle of length H[sub 2] that is attached to the top plate of a parallel-plate capacitor. The finite element method is used to solve the Young-Laplace equation for drop shape and the boundary element method is used to solve an integral equation for the electric field distribution on the drop and solid surfaces. The new results suggest that immediately upon loss of equilibrium sonic pendant drops jet from their tips whereas others go unstable by ejecting annular jets from their periphery. The temporal evolution of the instability or jetting phenomena cannot of course be determined by the present static analysis. By repeatedly increasing the number of elements on drop surfaces, which would be prohibitively costly if the electric field were calculated by finite element or difference methods, the apparent cone angle at the tip of drops tending toward conical is determined. Although the apparent cone angle is a function of D, this angle is shown to lie between 40[degree] and 50[degree] when D = 0: it increases monotonically with nozzle length and is bound above by the Taylor limit of 49.3[degree]. Moreover, the variation of the critical field strength for instability [var epsilon], with plate spacing H and nozzle length H[sub 2] and the asymptotic values approached by [epsilon][sub c] as H and H[sub 2] grow without bound are also evaluated. These results are of primary importance in capillary electrohydrostatics and in the development and design of electrodispersion apparatus finding use in the production of ceramic precursor Powders and in chemical separations.

• DOE Contract Number: AC05-84OR21400
• OSTI ID: 5579445
• Journal Information: Journal of Colloid and Interface Science; (United States), Vol. 161:2; ISSN 0021-9797
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
DROPLETS
ELECTROSTATICS
HYDRODYNAMICS
BOUNDARY CONDITIONS
CALCULATION METHODS
CERAMICS
ELECTRIC FIELDS
NOZZLES
PRODUCTION
SEPARATION PROCESSES
SHAPE
STABILITY
FLUID MECHANICS
MECHANICS
PARTICLES
360201* - Ceramics
Cermets
& Refractories- Preparation & Fabrication
400105 - Separation Procedures