Fluid Dynamics
Chapter 12
Chapter 12: Fluid Dynamics
377
12
1. Flow Analogy
1.1 Foreword on Flow
Many people have difficulty conceptualizing the parameters which
govern flow. Learning the equations which predict the relationships
between flow parameters usually seems daunting. Before you de-
spair, there are two important points you should consider:
• You know much more about flow and hemodynamics than
you realize.
• If viewed the correct way, much of what you need to know
is relatively intuitive and interesting.
With these two points inmind,the following analogy was written to
give you a way to conceptualize some of the flow parameters without
first discussing the complexities of the equations and the circula-
tory system. From this analogy, the foundation will be constructed
for a few of the fundamental equations that govern fluid dynamics.
1.2 Flow Analogy
Pretend you are a child once again. You and a very large group of
playmates are investigating the basement of an old, large, vacated
building. At the base of one of the walls is a dark hole which was
once covered by a grating which now lays on the floor. You, along
with most of your friends, are afraid of the dark.
Unfortunately, for you and your friends there is one extremely
powerful bully in the group who forces you into the tunnel to see
where it goes. You proceed to crawl down the tunnel. The bully,
unsatiated by making only you miserable, decides to keep forcing
more andmore of your playmates into the tunnel. The tunnel is very
long and just wide enough to allow four of you to squeeze through
at the same time.
At one point the tunnel narrows so that there is room only for one
person at a time to pass through. Since the bully is pushing a constant
stream of your friends into the tunnel behind you, all your friends
are pushing you to get through the narrowing as fast as possible so
that they don’t get squashed.
As the tunnel returns to its normal width,you would like to continue
traveling down the tunnel as a group again. As each of you gets
pushed through the narrowing so fast, you can imagine that you
will all be slightly discombobulated and that it will take a little effort
to regroup and return to an orderly flow down the tunnel. Finally,
you reach the end of the tunnel which dumps into the basement of
a connecting building. As you get out of the tunnel, you realize that
you are hot, sweaty, and tired.
1.3 Flow Analogy Exercises
Answers Pg. 572-573
1.
The bully is analogous to which structure in the body?
a) The arterial system
b) The venous system
c) The heart
d) The liver
2.
Match the following:
a) The bully
1. blood vessels
b) The tunnel
2. heart
c) You and your friends
3. stenosis
d) Narrowing of tunnel
4. blood
3.
Volumetric flow was represented by
a) The bully forcing people into the tunnel.
b) The fact that all the children were warm and tired after
exiting the tunnel.
c) The speed with which children went down the tunnel.
d) The number of children per time who went down the
tunnel.
