1 Investigation of Wall Normal ElectroMagnetic Actuator for Seawater Flow Control

Abstract: ElectroMagnetic (EM) Flow Control deals with the concept of using in combination “wall-flush ” electrodes (j, DC current supply) and “sub-surface ” magnets (B, magnetic induction origin) to create directly local body forces (jxB) within a seawater boundary layer. Analytical, experimental and computational investigations of EM Flow Control are presented here. This work is intended to understand the basic mechanisms involved in turbulence intensity and skin friction reductions as well as in coherent structure extinction. First, EM actuator and its modes of action are described. This description includes: some general remarks on EM actuator; the set of equations suitable to EM control in seawater; and a selection of dimensionless parameters analysed in term of possible mechanisms of action. Second, some experimental investigations and visualizations of wall bounded flows under EM actuation are presented: near wall vortex around the actuator; suction zone above the actuator; wall jets around the actuator; boundary layers “suction- blowing”.