The motility of sperm flagella and cilia are based on a common
axonemal structure. In this article, we describe a fluid-mechanical
model for the ciliary and sperm axoneme. This fluid-mechanical model,
based on the immersed boundary method, couples the internal force
generation of dynein molecular motors through the passive elastic
axonemal structure with the external fluid mechanics governed by the
Navier-Stokes equations. We show recent numerical simulation
results for sperm motility and multiciliary interaction.