Manual – Starflow QSD Model 6527B and 6537A
Unidata Manual - 6527B and 6537A Starflow QSD User Manual 08 05 2023.docx
Page 100
In fast turbulent water, the peak
can be 500 mm/sec or wider
because of the range of velocities
present in eddies and swirls. The
following histogram is typical.
17.3.
Inherent Factors in Doppler Histograms
The width and shape of the peak displayed are
caused by a range of factors, all of which are
measured by the Doppler as a frequency shift.
Some of these factors are inherent in the method.
In flowing channels, there is always a range of
different velocities present, but even in “perfect”
conditions, with all water flowing at the same
velocity, the histogram displayed will still have a
characteristic “skinny bell” shape.
This is a composite of a variety of effects related to
using Dopplers to measure water velocity in
streams.
17.4.
Varying Angles as Particles Pass through the Main Beam
The acoustic beam
has a width or
spread, of about 3°.
The centreline of the
beam is aligned at
30° above horizontal
as a particle passes
horizontally through.