I am trying to make the following figure using pgfplots
.
\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{width=8cm,compat=1.5.1}
\usetikzlibrary{decorations.markings} % Arrows
\usepackage{caption}
\begin{document}
\noindent
\begin{minipage}{\linewidth}
\centering
\begin{tikzpicture}[scale=1]
\begin{axis}[ axis lines=left,
xmin=-.1, xmax=1.9, ymin=-1, ymax=22,
xlabel={$v$}, ylabel={$p$},
xtick =\empty, ytick=\empty,
]
% Compression (Work in)
\addplot[blue, domain=0.85:0.1, samples = 20, postaction={decorate},
decoration={markings, mark=at position 0.6 with {\arrow{>}}}
] { (0.85/x)^(1.4) }
[sloped, font=\small]
node[below, pos=0.7] {$s =$ const.};
% Heat addition
\addplot[ red, postaction={decorate},
decoration={markings, mark=at position 0.65 with {\arrow{>}}}
]
coordinates{ (0.1,20) (0.2,20)}
[ every node/.style={font=\small, text = black} ]
node[ left, pos = 0] {2}
node[right, pos = 1] {3};
% Expansion (Work out)
\addplot[ blue,domain=0.2:1.7, samples = 40, postaction={decorate},
decoration={markings, mark=at position 0.32 with {\arrow{>}}}
] { (1.7/x)^(1.4) }
[sloped, font=\small]
node[above, pos=0.3] {$s =$ const.};
% Heat removal
\addplot[ red, postaction={decorate},
decoration={markings, mark=at position 0.6 with {\arrow{>}}}
]
coordinates{ (1.7,1) (0.85,1) }
[ every node/.style={font=\small, text = black} ]
node[below, pos = 0] {4}
node[below, pos = 1] {1};
\draw[blue, -latex, line width = 1pt] (axis cs:0.15,5.5) -- (axis cs:0.35,7)
node[anchor = north east, pos=0.5, font=\footnotesize] {$\dot{W}_{\textrm{in}}$};
\draw[blue, -latex, line width = 1pt] (axis cs:0.4,5.5) -- (axis cs:0.6,7)
node[anchor = west, pos=0.9, font=\footnotesize] {$\dot{W}_{\textrm{out}}$};
\end{axis}
\end{tikzpicture}
\captionof{figure}{Ideal Brayton cycle}
\end{minipage}
\end{document}
- How can I get the annotation arrows (the one that indicate power e.g.
\dot{W}
to be of same length? - Right now I am specifying the start and end point co-ordiantes of the arrows. This means that if I need to move the arrow, I need to tweak the co-ordinates correctly. Is there a way to specify based on
pos
on the curve like that other annotations? - How can I adjust the spacing between the
s = const.
annotation and the corresponding curve? I would like to increase the spacing from the 3-to-4 path.
Best Answer
For 1. and 2.: using a technique exposed by Alain Matthes in one of his answers (that I cannot find right now), I placed a node with
south west
anchor along each one of the blue paths using thepos=
key; then I used those nodes to draw normal (orthogonal) lines; the length was increased using theshorten >=
andshorten <=
options. In this way, there's no need to use explicit coordinates and the length for both arrows is the same.For 3: you can use the
yshift=
option to the nodes control the spacing.