Hemodynamics
of
Large Arteries
127
(4.5.27)
a parameter, now known as the Womersley’s parameter was introduced:
aW=r
-
/:
(4.5.28)
w
=
2$h
(4.5.29)
fh
=
heart rate/sec
(4.5.3
0)
p
(1.06
g/cm’) and
q
(0.03
poise or
3
centipoise) are the density and
viscosity of blood, respectively and r is the inner radius of the artery.
This parameter also represents the ratio of the relative contribution of
inertia component
to
viscous component of blood flow. In other words,
it describes the ratio of the movement of blood mass to the retardation of
flow or flow resistance due to blood viscosity.
a,
is also dependent on
arterial lumen radius, thus, the smaller the vessel, the smaller the value of
a,.
Morgan and Kiely made assumptions to arrive at wave velocity and
damping coefficient
(a),
for r
=
r, and
a,>>l:
(4.5.31)
And for for
a,<<]
r
(4.5.3 2)
For extremely low frequencies, or in the case of very small vessels,
these equations can be compared to those derived earlier.
