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Data treatment
b
c
a
x
c
y
b
a
z
y
Plane ⊥c
Plane ⊥b
b
v
c
a
x
Plane ⊥a
Figure 4.25: Schematic view of the projection of the measured velocity components a, b and c to obtain the final
velocity vector v
The so obtained velocity components cover the whole measurement depth. As is can be seen on
Figure 4.26, the bottom of the flume is clearly detectable. Due to the high amount of velocity profiles,
it would be useful to detect the bottom automatically. In the present study tests were performed
to detect the ground 1 . The bottom was fixed at the level for which the velocity as well as
the variance were close to zero (absolute value below a given threshold). This method was tested
with success.
1. There was not enough time to program an automatic velocity profile treatment; therefore the
ground was detected manually, based on the described criteria.
EPFL Ph.D thesis 2632 - Daniel S. Hersberger November 9, 2002 / page 95