Environmental Engineering Reference
In-Depth Information
Minimum and maximum values of colorbar are calculated automatically by the
software.
The
gquiv
switch is related to a
quiver
call. For a given velocity field the
command depicts an arrow field. Input values are, aside from the mesh coordinates
x
and
y
, the velocity components
u
and
v
. The latter are obtained from the potential
by the
gradient
command:
[u,v] = gradient (-phi);
which corresponds to (
14.8
). In the example the arrows are plotted in yellow
(formal parameter
'y'
). Note that
quiver
can only be used for 2D flow fields
and equidistant meshes.
Figure
14.5
depicts the output of the groundwater flow example, as far as
developed to this point. The plot was obtained after zooming in the figure editor.
Flow towards the well is clearly visible. Visible also is the increase of velocity if the
well is approached.
Finally another graphic option is introduced. The
streamline
command
produces flowpaths, which are also based on the velocity field. Flowpaths trace
the flow of a particle within the flow field; for that reason the method is also called
particle tracing
. Flowpaths are identical to streamlines in steady state flow fields
and identical to contours of the streamfunction; see Chap. 15 for differences and
advantages/disadvantages compared to streamfunction plots.
5.4
10
5.3
5
5.2
0
5.1
5
-5
4.9
-10
4.8
-15
4.7
80
85
90
95
100
105
110
115
120
125
Fig. 14.5 Example graphic showing contours, colorbar and arrow field
