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Boundary effects on electrothermal convection in a dielectric fluid layer

Ravisha M., Raghunatha K. R., Mamatha A. L., Shivakumara I. S.

Archives of Thermodynamics

2019

Vol. 40, no 1

3--19

The instability characteristics of a dielectric fluid layer heated from below under the influence of a uniform vertical alternating current (AC) electric field is analyzed for different types of electric potential (constant electric potential/ electric current), velocity (rigid/free) and temperature boundary conditions (constant temperature/heat flux or a mixed condition at the upper boundary). The resulting eigenvalue problem is solved numerically using the shooting method for various boundary conditions and the solution is also found in a simple closed form when the perturbation heat flux is zero at the boundaries. The possibility of a more precise control of electrothermal convection (ETC) through various boundary conditions is emphasized. The effect of increasing AC electric Rayleigh number is to hasten while that of Biot number is to delay the onset of ETC. The system is more stable for rigid-rigid boundaries when compared to rigid-free and least stable for free-free boundaries. The change of electric potential boundary condition at the upper boundary from constant electric potential to constant electric current is found to instill more stability on the system.

Capillary instability of fluid cylinder under the effect of transverse varying electric field

Radwan A. E., Radwan H. A.

Mechanics and Mechanical Engineering

2004

Vol. 7, nr 1

151-158

The electrodynamic instability of a capillary dielectric fluid cylinder (radius a and density p) penetrated by a uniform axial electric field surrounded by a transverse varying electric field is investigated. A general dispersion relation to all possible axisymmetric modes of perturbation for all short wavelengths and long wavelengths is derived and discussed in detail. The model is capillary stable to axisymmetric modes if the longitudinal wave number normalized with respect to the jet radius is equal to or greater than 1.05757 and vice versa. The axial electric fields pervading the interior and the exterior ofthe cylinder are stabilizing or destabilizing for all disturbance modes according to some restrictions. The transverse varying electric field is purely stabilizing in the axisymmetric disturbances for all wavelengths. The electrodynamic force has a strong stabilizing influence in the axisymmetric mode and can suppress the capillary instability above a certain value of the basic electric field.