74

Dynamics

of

the

Vascular System

0

Fig.

3.3.5:

Illustration

of

laminar to turbulent flow transition as a function of Reynolds

number. Velocity transition from a parabolic profile to a blunt profile is also seen. From

Nichols and O’Rourke

(1998).

The most important observation and quantification made by Reynolds

is in the differentiation

of

turbulent flow from laminar flow.

This means

that the turbulence depends not only on the average velocity v

of

the

fluid, but also depending on the fluid property and the lumen diameter d.

The laminar to turbulent flow transition is shown in Fig.

Reynolds number

of

is assumed when turbulence begins.

The

Mach number is invariant among mammalian blood vessels, but the

Reynolds number is dependent on body size (Li,

2000).

Turbulence that

normally occurs with high Reynolds number is somewhat constrained in

a larger mammal’s aorta by the larger compliance (Li,

1988).