Staggered actuation of electromagnetic tiles for boundary layer control

An apparatus for controlling a boundary layer in a flow of an electrically conductive fluid moving relative to a surface in a free-stream direction, said apparatus comprising:

• a plurality of selectively actuatable control region tiles distributed over the surface in an array extending in the free-stream direction and a direction transverse thereto, each said tile being bounded by magnetic field generating means for generating in the fluid a magnetic field B(x,y,z,t) having flux lines with a predetermined orientation with respect to the free-stream direction and electric current generating means for generating in the fluid an electric current density J(x,y,z,t) traversing the magnetic flux lines such that actuation of a particular tile generates a magnetic field B and electric current density J that create in the flow a force L(x,y,z,t)=J.times.B and introduce a resulting vorticity distribution .omega. (x,y,z,t);
• and
• control means for selectively actuating said tiles to create control regions that introduce a vorticity distribution into the flow over each said control region such that over said array the vorticity at the wall in the direction transverse to the free-stream direction is reduced and creation of boundary layer vorticity concentrations in the free-stream direction is inhibited.