  Scaling laws for the propulsive performance of rigid foils undergoing
oscillatory heaving and pitching motions are presented. Water tunnel
experiments on a nominally two-dimensional flow validate the scaling laws, with
the scaled data for thrust, power, and efficiency all showing excellent
collapse. The analysis indicates that the behaviour of the foils depends on
both Strouhal number and reduced frequency, but for motions where the viscous
drag is small the thrust closely follows a linear dependence on reduced
frequency. The scaling laws are also shown to be consistent with biological
data on swimming aquatic animals.
