
Figure 46f Schematic illustrating the relation between
flow velocity and pressure drop across a discrete obstruction. Proximal
to the obstruction, flow is laminar (parallel arrows) and velocity V1
is normal. At the level of the obstruction, and just beyond, flow remains
laminar and velocity V2 is increased. the pressure drop P1P2 across
the stenosis can be calculated from the velocities by the modified Bernoulli
equation. Since V1 usually is considerably smaller than V2, the instantaneous
pressure drop can be determined from the instantaneous velocity(V) in
the stenotic jet. 