Author: Md. Abdul Halim

Publisher:

Published: 2013

Total Pages: 406

ISBN-13:

Management of bubbles, drops, and solid particles is a major task in many industrial processes. For almost all conventional applications, the gravitational force is predominantly used to control and manipulate their motion. In the cases where the gravitational force can no longer serve the purpose, particle control by electric field is a promising alternative. Thus, the electrohydrodynamic phenomenon, which deals with the interaction of fluid flow and electric field, is being studied in many physical, chemical, and engineering disciplines. Some of the prominent applications are microelectromechanical devices, enhancement of heat and mass transfer, and electroseparation devices (electrophoresis units, electrodialysis cells, and electrically driven desalters). In this thesis, the dynamics of drops suspended in AC electric fields were studied using Direct Numerical Simulations (DNS). The Navier-Stokes equation and the electrostatic equation were solved for the fluid inside and outside the drop. Several sets of simulations were performed concerning the dynamics of a single drop. The single bubble simulations captured the transient behavior of the drop, flow, and the electric field toward the quasi-steady state. Low surface tension drops readily deformed to oblate or prolate shapes while drops having high surface tension remained circular or went through rebound before reaching a quasi-steady state. The multibubble simulations showed the significance of the relative magnitude of the conductivity ratio (R) and the permittivity ratio (S), of the fluid drop to the ambient fluid, in the microstructure formation of the drops. When S>R, the drops tended to deform to oblate shapes and accumulate in the middle of the domain. For S The multibubble simulations showed the significance of the relative magnitude of the conductivity ratio (R) and the permittivity ratio (S), of the fluid drop to the ambient fluid, in the microstructure formation of the drops. When S>R, the drops tended to deform to oblate shapes and accumulate in the middle of the domain. For S