Alternating‐Current Generation with Moving Conducting Fluids

A one‐dimensional, small‐amplitude analysis is presented of alternating‐current generation by a stationary electromagnetic circuit coupling to waves in a moving, perfectly conducting fluid. In a uniform applied dc magnetic field the waves in the fluid are either compressional waves if the time‐average velocity v0 is transverse to the dc magnetic field, or Alfven waves if it is along the dc magnetic field. It is shown that, for velocities v0 greater than the velocity of propagation c of the compressional or Alfven waves, self‐excited oscillations may be produced in a resistively loaded coil coupling to the fluid. In a traveling‐wave circuit and in a resistively loaded distributed circuit coupling to the fluid, growing waves are found which result from a transformation of the fluid energy into electromagnetic energy. There is a close analogy between these power‐generation mechanisms and those employed in microwave electron‐beam tubes.The results of two‐ and three‐dimensional analyses are summarized in orde...