The
Venous
System
1
87
(6.3.1
1)
where
kQ
is
an empirical expression
<Q/Q,>
k-
’
-
[1+(Q/Qc)6]l-”6
(6.3.12)
where
Qc
is the critical flow when the plateau is reached.
It
is an
empirically derived function and is dependent
on
the values
of
pe-p2 only.
Otherwise, the whole relation reduce to that of a steady flow through
the tube with circular cross-section:
pi
-
~2
=
RQ
(6.3.14)
An
axially stretched Penrose tube showed no plateau (Brower and
Noordergraaf,
1978)
when Ap is plotted against flow.
30
.
-
P,-Pr’30
’I
-
25
.
20
15
10
5
Ro
5
10
15
20
cmK
Fig
6.3.3:
Pressure gradient (Ap =p1-p2) and flow (Q) relation in a collapsible Penrose
tube, while
pe-p2 is
varied. Ro
is
the equivalent Poiseuille resistance when tube is open
From Noordergraaf (1
978).
