The concept of modifying the turbulent boundary layer with a conformal
array of electrodes and permanent magnets used to produce a
spatially- and temporally-varying Lorentz force
for the primary purpose of drag reduction will be presented.
This approach is called ElectroMagnetic Turbulence Control, or EMTC.
The basic physics of EMTC, along with implementation
on a flat plate and an autonomous buoyant axisymmetric body will be discussed.
The buoyant test vehicle (BTV) permits a direct determination of
EMTC effectiveness from: 1. arrival time at the free surface,
2. velocity at breach, and 3. breach height.
In particular, the breach height alone may be used to determine directly the
mean BTV-drag during ascent.
In a preliminary, related experiment, a circumferential array of
modified EMTC tiles introduced a net streamwise component of Lorentz force
in the vicinity of the BTV tail. The objective was to maneuver the BTV
during rise (in pitch and yaw) through the generation of azimuthal
variations in the local tail-pressure to create a net moment about the
center of mass of the BTV. Visual observations of the BTV during
these initial "solid-state" maneuvering experiments will be presented.