Electrohydrodynamic flow modeling using FEMLAB

Karpov, S., Krichtafovitch, I.
Kronos Air Technologies, Redmond, Washington

Electrohydrodynamic flow is a flow of electrically neutral gas caused by corona-generated charged particles (ions) drifting through it. The operation principles of electrostatic fluid accelerators that use corona discharge phenomenon can be described as following. High voltage applied between high curvature corona electrode and low curvature collecting electrode provides condition for ionization of gas molecules in the nearest vicinity of corona electrode surface.

In the case of positive corona, i.e. where corona electrode has potential higher than collecting electrode, negative ions move toward corona electrode whereas positive ions move away from it, eventually leaving the ionization zone. Outside the ionization zone, positive ions drift toward collecting electrode and collide en route with neutral air molecules. During these collisions, momentum is transferred from ions to neutral molecules resulting in a bulk motion of the gas. Thus, electrohydrodynamic flow involves interaction between the electrostatic field, the flow of ions, and the flow of electrically neutral gas molecules. In addition, if collecting electrodes have finite conductivity, then voltagecurrent distribution inside them also has to be taking into account.

This paper shows how modeling of electrohydrodynamic flow can be successfully performed using FEMALB multiphysics modeling capabilities. Four application modes are used to solve system of coupled equations with appropriate boundary conditions: Electrostatics mode for electric potential distribution in drifting zone, PDE (Coefficient Form) mode for charge transport equation, Incompressible Navier-Stokes mode for fluid dynamics equations, and Conductive Media DC mode for electric potential distribution inside conductive collecting electrodes.