Introduction to CFD — GNUPLOT HOWTO  
x-y plot
First create a post file suitable for gnuplot as follows (data interpolated along $y=0$):
INTROCFD.201325962:~> warp -r test.wrp -i data.01 -op post.01 -pt gnuplot -py 0.0
Open the gnuplot shell:
INTROCFD.201325962:~> gnuplot
Type the following within the gnuplot shell to plot density (column 7) versus $x$ (column 1):
plot 'post.01' using 1:7
If you want to compare two (or more post files), enter the following:
plot 'post.01' using 1:7, 'post.02' using 1:7
02.20.18
Grid plot
First create a post file suitable for gnuplot as follows:
INTROCFD.201325962:~> warp -r test.wrp -i data.01 -opg post.01 -pt gnuplot
Open the gnuplot shell:
INTROCFD.201325962:~> gnuplot
Type the following within the gnuplot shell:
reset

set view map; set key outside; unset key; set size ratio 0.8; set xlabel 'x, m'; set ylabel 'y, m'

splot 'post.01' using 1:2:2 with lines
Grid plot with contour levels
First create a post file suitable for gnuplot as follows:
INTROCFD.201325962:~> warp -r test.wrp -i data.01 -op post.01 -pt gnuplot
Open the gnuplot shell:
INTROCFD.201325962:~> gnuplot
Type the following within the gnuplot shell to plot the grid with the color of the grid lines matching the contour levels of property #7 (density):
reset

set view map; set key outside; unset key; set size ratio 0.8; set xlabel 'x, m'; set ylabel 'y, m'

splot 'post.01' using 1:2:7 with l lc palette
Vector plot
First create a post file suitable for gnuplot as follows:
INTROCFD.201325962:~> warp -r test.wrp -i data.01 -op post.01 -pt gnuplot
Open the gnuplot shell:
INTROCFD.201325962:~> gnuplot
Type the following within the gnuplot shell to make a plot of the velocity vector (with the vectors scaling with the variable “scale”):
reset

set key outside; unset key; set size ratio 0.8; set xlabel 'x, m'; set ylabel 'y, m'; set macros; with_vectors = "using 1:2:($3*scale):($4*scale) w vectors"; scale = 0.001

plot 'post.01' @with_vectors
Contour plot
First create a post file suitable for gnuplot as follows:
INTROCFD.201325962:~> warp -r test.wrp -i data.01 -op post.01 -pt gnuplot
Open the gnuplot shell:
INTROCFD.201325962:~> gnuplot
Type the following within the gnuplot shell to make a filled contour plot of the density (post file column number 7):
reset

unset key; unset surf; set view map; set contour base; set size ratio 0.8; set xlabel 'x, m'; set ylabel 'y, m'; set palette rgbformulae 22,13,10; set cntrparam levels 100

splot 'post.01' using 1:2:7 with l lc palette lw 1.5
Filled contour plot
First create a post file suitable for gnuplot as follows:
INTROCFD.201325962:~> warp -r test.wrp -i data.01 -op post.01 -pt gnuplot
Open the gnuplot shell:
INTROCFD.201325962:~> gnuplot
Type the following within the gnuplot shell to make a filled contour plot of the density (post file column number 7):
reset

set pm3d; unset surface; set view map; set key outside; unset key; set xlabel 'x, m'; set ylabel 'y, m'; set size ratio 0.8; set palette rgbformulae 22,13,10; set cntrparam linear; set pm3d interpolate 4,4

splot 'post.01' using 1:2:7
02.28.18
Color palettes
Traditional PM3D:
set palette rgb 7,5,15
Rainbow:
set palette rgbformulae 22,13,10
Hot:
set palette rgb 21,22,23;
Ocean:
set palette rgb 23,28,3
Grayscale:
set pal gray
Large Rainbow:
set palette model HSV; set palette rgb 3,2,2;
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