  The motion of a rotating helical body in a viscoelastic fluid is considered.
In the case of force-free swimming, the introduction of viscoelasticity can
either enhance or retard the swimming speed and locomotive efficiency,
depending on the body geometry, fluid properties, and the body rotation rate.
Numerical solutions of the Oldroyd-B equations show how previous theoretical
predictions break down with increasing helical radius or with decreasing
filament thickness. Helices of large pitch angle show an increase in swimming
speed to a local maximum at a Deborah number of order unity. The numerical
results show how the small-amplitude theoretical calculations connect smoothly
to the large-amplitude experimental measurements.
