Page 203 - Instrumentation Reference Book 3E

Doppler anemometry 187

I Beam \

1 lo Transm'itting \ /

I
E
1 1
Figure 12.21 Schematic illustration of the dual-fiber method for Doppler blood flow velocity measurement (Kajiya et al.
1988).

Fiber core Emission cone
Transmitting fiber, \ \/

/
M
/. ~ I u fbw medium
Receiving fiber
Fiber disturbed cone
flow region

Unshfted zero vebcity
"noise" signal
<: flow towards probe
Fbw away from Free flow velocity
Doppler signal-

I 4 nt % 8
# t
# 8
Frequency (Hz) +
0
Figure 12.22 Schematic of (a) the sampling volume for the dual-fiber method in the free flow velocity region, and (b) a
spectrum analyzer type output signal indicating a free-flow Doppler signal (Kajiyal et al. 1988).

orientation. The calibration was performed with used to make accurate flow velocity measurements
the fiber probe at an angle of 60" in a rotating even in disturbed flow fields.
turntable containing blood, and a good correlation
was observed between the Doppler frequencies and
the equivalent flow velocities, with correlation 12'4*4 Vibration monitoring
coefficients of r = 0.985 in the direction of flow There have been several successful examples of
and r = 0.998 when against the direction of flow. the application of optical fiber sensor systems to
This optical fiber measurement system can thus be the non-contact measurement of vibration and at