Most of the fundamental concepts of unsteady viscous flows have been known since the early part
of the century. However the past decade has seen an unprecedented number of publications in
this area. In this monograph I try to connect materials of earlier contributions and synthesize
them into a comprehensive entity. One of the main purposes of a monograph in my opinion is to
fit together in a comprehensive way scattered contributions that provide fragmented information
to the readers. The collection of such contributions should be presented in a unified way
continuity of thought and logical sequence of the presentation of ideas and methods are
essential. The reader should be able to follow through without having to resort to other
references something that is unavoidable in the case of a research paper or even a review
paper. Many of the solutions discussed in the literature address specific practical problems.
In fact in the process of collecting information I discovered independent lines of
investigations dealing with the same physical problem but inspired by different practical
applications. For example I found that two groups of investigators have been studying
independently the response of a viscous layer to a harmonic external disturbance. One group is
con cerned with mass transport and the transport of sediment over the bottom of the ocean and
the other is interested in the aerodynamics of lifting surfaces in harmonically changing
environments.
