Fig. 5 shows the static pressure distribution in a duct with a
rectangular leak (with an aspect ratio 3) and with an inlet velocity
of 2.0 m/s (Re 27,000). The static pressure drop along the length
of the duct decreases in the flow direction owing to frictional loss.
The static pressure drop in the duct at different cross sections in
the flow direction has been plotted in Fig. 6. The average static
pressure at each section was calculated as the area average of the
static pressure of the cells lying on that particular section. The slope
of the line AD is
−0.52 and that of line GI is
−0.3 in Fig. 6. The
change in the slope indicates that the flow is not completely developed
in the first section upstream of the leak and the slope of that
line decreases downstream of the leakage partially because the net
flow in the duct has decreased downstream and because the flow
is approaching it fully developed profile.