The rectilinear flow of an incompressible viscous fluid
along a duct of uniform cross section due to an
oscillating pressure gradient has been considered by
a number of investigators. The duct of circular
cross .section has been treated by Richardson and
Tyler and Sexl, the elliptic case by Khamrui, and
the rectangular case by Drake and Fan and Chao.
Recently Jeng has discussed the importance of this
type of flow and has given a procedure for
calculating a numerical solution for a duct of
arbitrary cross-section. An interesting feature of
these flows is that, at large frequencies when the
flow is of boundary-layer type, the velocity at any
instant has its maximum near the walls, the velocity
overshooting its almost uniform distribution at the
centre of the duct.