Water is first caused to flow through a first passage and rotate a first
impeller. Rotation of the first impeller is linked to rotation of a second
impeller, which is in fluid communication with a second, discrete passage.
Vanes on the second impeller are constrained to move faster than vanes on
the first impeller. Water is subsequently caused to flow through the
second passage and to be more aggressively advanced by the second
impeller.
