Abstract:
The reader will quickly see that the subject
matter of Chapter 3 is confined to the hydraulics of sharply
stratified media, whereas real estuaries are always more or
less diffusely stratified. What is more, no discussion is
made of the order of magnitude of the friction terms. In
ordinary single layer flow (such as in rivers) engineers already have crude approximations of the friction terms (Chezy
and Manning formulas), but we do not have even these approximations for two layer flow. For this reason the differential
equations of gradually varied flow of two layers are for the
most part left unintegrated and all that is demonstrated is
the qualitative aspects of the flow.
In the case of entrainment of water from one layer
into another we can only perform integrations of the equations when the amount of entrainment is known, whereas in real estuaries we do not have a priori knowledge of this amount.
The reader will see, therefore, that the subject matter
of Chapter 3 is really very incomplete, leaving undetermined all the constants which depend upon turbulent mixing,
upon the frictional stresses on the bottom, and the
free surface and the walls, and upon the amount of entrainment.
The contents of Chapter 4 are somewhat different.
First of all, they contain summaries of several
of these papers have proceeded on the basis of hypotheses already published papers on the mixing in estuaries. Most
about the nature of the mixing process. The applicability
of these hypotheses appears to be restricted to only certain estuaries, and it must be admitted that more work has
been done that involves guessing what the mixing processes
in an estuary might be, than has been done in trying to
find out what the mixing processes in an estuary actually
are.
As incomplete as the subject matter of Chapter 4
is, it is hoped that it will suggest which of the possible
mixing processes in estuaries may be important in any particular
one which is the subject of study, and that it will
also suggest the type of observations which will be most
desirable in studying a particular estuary. For example:
in an unstratified estuary it seems that a more or less
uniform spacing of stations up and down the estuary is desirable; but in an estuary which appears to be subject to
the constraint of overmixing (Section 4.51) the location of
stations should be largely confined to control sections.
