Drag reduction by dc corona discharge along an electrically conductive flat plate for small Reynolds number flow

Abstract

Corona-induced drag reduction was studied numerically over a finite region of a semi-infinite flat plate having small Ohmic surface conductivity for low Reynolds number flow (<100 000, based on the farthest downstream electrode distance). The model simulates a corona discharge along a surface from two parallel wire electrodes of infinite length immersed flush on the surface and oriented perpendicular to the flow. Charge deposition and removal with the conducting surface are included as possible charge transfer mechanisms. The analysis is limited to ions of positive charge. Five coupled partial differential equations govern the numerical model including continuity, momentum, gas phase conservation of charge, Poisson’s equation of electrostatics, and conservation of charge at the solid interface. The governing equations together with empirical breakdown and current–voltage relationships (Φ–I characteristic) were evaluated by finite differencing schemes. The calculated results predict “corona thinning” of the boundary layer for a downstream ion flow and a corresponding reduction in drag, in agreement with previous theoretical studies. Various parameters of flow, electricity, and geometry, relating to corona-induced drag, are investigated.