The
Venous
System
183
where p
is
the static pressure and po is the stagnation pressure and
p
is
density of the fluid and v
is
flow velocity. The volume flow rate is
obtained as the product of the cross-sectional area and the average
velocity, i.e.
A
is the cross-sectional area which is a function
of
p-pe. Conservation
of
mass states that
Q
remains constant along the tube, despite that p varies
with distance down the tube. If po-pe
is
fixed, then the flow rate changes
with p-pe:
(6.3.4)
Pulse wave velocity can be derived with modification of the Moens-
Korteweg formula. Area elasticity can be used instead
of
volume
elasticity. Phase velocity
of
propagation in terms
of
pressure-cross-
sectional area relation can be written as
or
Thus, equation (3) becomes:
(6.3.5)
(6.3.6)
(6.3.7)
Thus, flow will increase with decreasing p-pe, only if v<c. Flow reaches
its maximum and limitation occurs when v=c.
If
v>c, then
a
further
