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\title[Notation and style guide]{Journal of Fluid Mechanics:\\%
       notation and style guide}
\author[L. J. Drath]{L.\ns J.\ns D\ls R\ls A\ls T\ls H}
\affiliation{Department of Applied Mathematics and Theoretical Physics, \\%
       Silver Street, Cambridge CB3 9EW, UK}
\pubyear{1993}
\volume{0}
\date{8 September 1993}

\begin{document}
\maketitle
\section{Introduction}
This document describes {\it Journal of Fluid Mechanics}
house style and notation, i.e.\ editorial matters concerning the content of the
paper. It is intended to complement the Input Guide to the
{\it JFM\/} \LaTeX\ style file, and so does not include general matters of
layout and numbering which the style file handles automatically, or  
information on using \LaTeX, which can be found in the Input Guide or the \LaTeX\ Manual.

Most editorial queries concerning notation and house style can be answered by
looking at recent pages in the {\it Journal}. The more important points are
noted in the following sections, and further information and examples
can be found in the Input Guide (JFMguide.tex) and sample pages (JFMsampl.tex).

It is very important that the guidance on style given in these pages
is followed:
editorial changes to the author's file will normally be done by the
printer, but if there are many of them, the disk may be returned to
the author for correction, thus delaying publication.

For quick reference, a summary of the most important points to note follows:
\begin{itemize}
\item Use a roman typeface in maths for:  the d (or D) in
differentials and integrals; i (square root of -1); e (exponential);
units and abbreviations (but all sub- and superscripts, apart from
those just listed, are italic)(see \S\,5.2.1).
          
\item  Use the appropriate typeface for vectors, matrices and tensors 
(\S\,5.2.1).

\item  Use $(......)^{\frac{1}{2}}$   not  $\sqrt{.....}$ (\S\,5.2.2).

\item  Put punctuation after equations where appropriate (\S\,5.1).

\item  Do not use small fractions  ($\frac{gh}{u}$),  except for
numerals ($\frac{1}{2}$,  $\frac{2}{3}$ etc.\ ): in the text use $gh/u$
and in displayed maths use $gh/u$ or normal sized fractions (\S\,5.1).

\item  Letters ({\it a, b}, etc.) associated with  equation numbers,
figure or table  numbers and references are italic, and for figures
and tables are in brackets unless they are in a phrase that is already
in brackets (\S\S\, 5.1,  3, 4).

\item Use British spelling (centre, behaviour, modelling, emphasize,
etc.)  (\S\,8).

\item  Hyphenate compound adjectives, e.g.\ high-frequency wave,
solid-body rotation; and use a double hyphen (en rule) to indicate
`and' or `to', e.g.\ Navier--Stokes, pressure--strain, pages 45--56 (\S\,9).

\item  When a reference has three authors, on first mention in the
text {\em all three\/} authors must be listed, and \etal used
thereafter; use \etal from the start if there are four or more authors (\S\,2.7.2).

\item  If a string of references in the text is in brackets, do not put
brackets round the dates; separate the entries by semicolons (\S\,2.7.2).

\item  Follow {\it JFM\/} style in the form and ordering of the list of 
References (\S\,2.7.1).
\end{itemize}

\section{General structure}

\subsection{Title}
The title should be simple and concise. Only the first word is
capitalized, apart from proper names. If the paper is part of a series 
then the title is styled `Annular flow. Part 3. Experiments'.

\subsection{Authors and affiliations}
Authors' names appear together on the same line, capitalized.
Addresses are listed separately below, with a superscript numeral to
link each author to the appropriate address if there are more than one.
Postal addresses must be given in full, including zip codes or the
equivalent, and the country. A new address can be indicated in a footnote
to the author's name if necessary.

The `received' and `revised' dates will be inserted by the Editorial Office.

\subsection{Abstract}
The abstract should be self-contained and self-explanatory and contain a
summary of purpose, methodology, results and conclusions. References and
displayed equations should be avoided.

\subsection{Section headings}
Only the first word of the heading is capitalized, apart from proper names.
{\em In the text\/} use the symbol \S \, instead of spelling out the word 
section, except at the start of a sentence. Section headings are bold, so any
maths symbols not normally bold, i.e.\ not vectors, should be changed to italic (see Input Guide).

\subsection{Acknowledgements}
Any financial support should be mentioned here. Dedications are not normally
permitted.

\subsection{Appendices}
Any appendices appear between the acknowledgements and the references.

{\em Long detailed appendices of interest to a few readers only are not
printed, but are held in the Editorial Office and made available on request.}

\subsection{References}

\subsubsection{The list of references}
Most papers submitted to the {\em Journal\/} require editorial changes to the
references, so please take particular care in the preparation of the list.

References are listed at the end of the paper in strict alphabetical
order (i.e.\ not ordered according to the number of authors or date). If the
same author(s) has more than one publication in the same year, then {\it a,
b,} etc.\ should be added after the year.  Private communications are not
included in the References; when they are mentioned in the text, initials of
first names must be given. Articles that are `submitted' or `in press' may be
included provided that the full title and the name of the Journal are given. 
Non-published material not widely available should be avoided.

The style of the References can be seen in any recent volume of the
{\em Journal} and examples are given at the end of the Input Guide. Titles
and last page numbers of articles are preferred, but can be omitted  if
done consistently. Titles of theses must be included. There is no need to
add any part of the address of the publisher, nor words such as `Press' or
`Verlag' that follow the publisher's name (except for University Presses,
where omission of Press could cause confusion). Conference proceedings must
include the editor(s) and publisher.

Short titles of Journals are based in general on the style of the {\em World
List of Scientific Periodicals}. Note that letters denoting series are
printed in roman type, e.g.\ {\em Proc.\ R. Soc.\ Lond.} A {\bf 432}, and
that contractions (e.g.\ Engng, Intl) are not followed by a point.

\subsubsection{References in the text}
The Input Guide gives details of using a key to cross-reference entries in the References and the text.

References in the text should include the author(s) name, and the
year in parentheses, unless the reference is already in parentheses, e.g.\
see Smith (1989) or (see Smith 1989). Strings of references in parentheses
should be separated by semicolons, with no commas before the dates, e.g.\
(Jones 1967, 1978; Tam 1980; Dog 1991). Any page or section numbers etc.\
referred to should follow the date, after a comma e.g.\ Smith (1987, 
p.~234).

If there are three authors, all the names are given at first mention, then
just the first name and \etal subsequently. When there are four or
more authors \etal is used from the start.


\section{Figures}

Figures cannot at present be handled in electronic form, so hard copies 
need to be provided. However, they should be included in the text in the 
form of a dummy amount of blank vertical space with the caption.

Colour pictures have to be paid for by the author and can be separate
glossy plates or printed within the text like other figures.

Figures must be numbered sequentially in the order in which they are mentioned in the text, each with a caption.

Large areas of white space should be avoided, and complicated information
should appear in the caption rather than on the figure. Avoid duplicating
information on the figure and in the caption. Groups of similar
figures should be numbered as parts ({\it a}), ({\it b}), etc.\ of
the same figure, with a single caption.

In the text, the word `figure' is never abbreviated, and only capitalized at
the start of a sentence. Do not put parentheses around  {\it a, b\/}
etc.\ if the phrase is already in parentheses. The following are
examples of forms: figure 1; figure 1\,({\it a,\,b\/}); 
figure 1\,({\it a--e\/}); figures 1\,({\it a\/}) and 1\,({\it b\/}); 
(figure 1\,{\it a,\,b\/}); (figures 1\,{\it a\/} and 1\,{\it b\/}).

\section{Tables}
Tables, however small, must be numbered sequentially in the order in which
they are mentioned in the text (where the word `table' is only capitalized at
the start of a sentence). Each should have a caption.

There should be zeros before decimal points for numbers less than one, and
powers of 10 rather than `e-4' etc.\ should be used.

{\em Extensive detailed tables of interest to a few readers only
will be held in the Editorial Office and made available on request.}

\section{Mathematics}

Details of how to use \LaTeX\ to obtain the notation and style described in
this section can be found in the JFM Input Guide or the \LaTeX\ Manual.

\subsection{Layout of equations}
Long, complicated or important equations are displayed, but
punctuated as part of the text. Numbered equations appear on separate lines,
but related equations may be denoted (2\,{\it a\/}), (2\,{\it b\/}), etc. In
this case, if they are short, they should be on the same line, separated by a
space, and then numbered in the style (2\,{\it a,\,b\/}), (2\,{\it a--c\/})
etc. Two or more equations on separate lines but with the same number should
be braced together. Dislayed equations are centred and long ones should be
broken before a $+$ or a $-$ sign. The symbol $\times $ should be used if the
break has to be at a product. Words such as `for', `as' should be roman type
with an em space on each side (see \S 5.2.1 for other details on typefaces).

Small fractions should only be used for numerals. To save space, short simple
fractions should be typed with a slash rather than on two lines.

Complicated expressions should be represented by a symbol rather than being
written out in full each time.

\vspace{3 mm}

When equations are referred to {\em in the text}, only the number in
parentheses need be given, e.g.\ `substituting (3.12) into (3.20) we
obtain...' (avoid using numerals in parentheses for any other reason): the
word `Equation' is only needed at the start of a sentence and should never 
be abbreviated. Non-displayed equations within the text must be short and
simple, and fractions must be on one line only, with a slash.

\subsection{Mathematical notation}
\subsubsection{Fonts}
Mathematical symbols are usually printed in the italic or sloping greek
type normally produced by \LaTeX\.  Avoid multiletter symbols such as
$KE$ for kinetic energy -- use $E_{K}$ instead. However, they are
sometimes used for dimensionless numbers such as {\it Re, Pr} for Reynolds 
or Prandtl numbers, and then spacing between the two letters should 
be smaller than in normal \LaTeX\ maths mode -- see the Input Guide.

Non-italic fonts should be used as follows (see the Input Guide for
how to obtain these fonts):
\begin{itemize}
\item
{\em Roman\/}: roman type should be used for the following:
  \begin{description}
    \item to denote mathematical operations, e.g.\ sin, log, d (differential);
    \item constants e.g.\ i ($\sqrt{-1}$), exp or e;
    \item Ai, Bi (Airy functions);
    \item Re, Im (real, imaginary);
    \item physical units (cm, s, etc);
    \item abbreviations such as c.c.\ (complex conjugate) and h.o.t.\
          (higher-order terms).
  \end{description}

(Note that some sub- and superscripts used to be printed in roman type
but they are now italic, apart from any in one of the above
categories.)

Greek letters are styled equivalently, i.e.\ slanted for mathematical
variables, but constants such as pi and mu (micro) and operators such as $\Delta$ (difference) are upright. 
\item
{\em Bold italic or bold sloping greek\/}: for vectors
($\bnabla$ should also be bold, but not $\nabla^{2}$).
\item
{\em Bold sloping sans serif\/}: for tensors and matrices.
\item
{\em Script\/}: an alternative to italic when the same letter is used
to denote different quantities.
\end{itemize}

\subsubsection{Symbols}
Square roots should be denoted by brackets and a fractional exponent
$(...)^{\frac{1}{2}}$ rather than the root sign $\sqrt{...}$.

A symbol is not normally used to denote a product: use a multiplication
symbol only when breaking a displayed equation, for vector products or
between numbers, e.g.\ $106 \times 10^{4}$; use a point only for the scalar
product of vectors.

Use $\approx$ to denote `approximately equal to '

Use $\sim$ to denote `asymptotically equal to'

Use {\it O} to denote `of the order of'.

\section{Units}

The International System of Units (SI) should normally be used.
An exponent is preferred to a solidus, e.g.\ cm s$^{-1}$. There should be
a space between a number and its units, and there is no need to repeat the
units in a list, e.g.\ 5 and 6$\;$cm.

Use a low rather than centred decimal point.

Use \% instead of writing out `percent' and $^{\circ}$  instead of `degrees'.
On a figure the axis label should be (deg.), though, rather than using the
symbol by each number.

\section{Abbreviations}

Only commonly accepted abbreviations can be used, and they must be
defined at first occurrence. There should be points between lower-case
letters in an abbreviation, but not between capital letters. There is no
point after a contraction, engng for example.

Do not use the following abbreviations: 2-D, 3-D, l.h.s., r.h.s., fig., eq.

\section{Spelling and capitalization}

Use British spelling conforming to the preferred spelling in the {\em
Shorter Oxford English Dictionary}. Examples include behaviour, colour,
centre, travelling, modelling, emphasize, zeroth, analyse.

Use initial capital letters for proper names and their derivatives, e.g.
Gaussian, Lagrangian, Cartesian, Pitot, Perspex, Plexiglas. Figure, table,
section should not be capitalized.

\section{Punctuation and hyphenation}

Hyphens should be used between compound adjectives, e.g. large-scale
region, low-frequency wave, solid-body rotation, first-order equation (but
only when preceding the noun, e.g. 'equation of first order' has no hyphen).
Self, cross and half are always followed by a hyphen (e.g.\ self-interaction,
cross-section, half-width), and a hyphen s follow `non', apart
from nonlinear. Nouns with prefixes and compound nouns should normally be one
word (e.g.\ coordinate, cutoff, breakup, predetermined, bandwidth, subgrid)
unless there is a repeated letter (e.g.\ semi-infinite, over-relaxation).
Other examples of nouns that are normally printed as one word include
wavenumber, wavelength, sidewall, arclength.

En rules (keyed as a double hyphen) should be used when replacing `and' or
`to', e.g.\ gravity--capillary, Navier--Stokes, 10--20 cm. A comma is not
needed after an abbreviating point, for example e.g.\ i.e.\ or cf.\ nor
between lists of adjectives, e.g.\ long thin slow-moving cylinder. When a
complete sentence is inside parentheses, then so is the final full stop.

\section{Some miscellaneous style points}

Avoid footnotes since they interrupt the reading of the text.

Separate lists of nomenclature are not normally permitted. Symbols should be
defined and explained on first appearance in the text.

Italics should seldom be used for emphasis, but may be needed in definitions
and for foreign words.

\end{document}

