Thermo Scientific HB-S2000, User Manual

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Sarasota 2000 Ultrasonic Multipath
Flowmeter
Section 1 INTRODUCTION Page 1-4 Thermo Fisher Scientific
INTRODUCTION
1.2.5.1 Mid section method
In the mid section method, the slice boundaries are defined by lines mid way between the
paths. The slice velocity is taken as that determined by the path within the slice and the slice
area as the product of the slice height and the (average) width. The upper boundary of the top
slice is the water surface. At the bottom, an additional slice is defined between the bed and a
line half way between the bed and the bottom path. This bottom slice has a weighting factor,
K, normally between 0.4 and 0.8 to allow for the slow moving water near the bed. To reduce
the uncertainty of this factor, the bottom path should be positioned as close to the bed as
practical.
Illustration of the mid section method for 4 paths
Height H
S
Path 4 Height H
4
Water Surface
Width W
4
Bed Height H
0
Bottom panel
Top panel
½(H
4
+ H
3
)
Width W
3
Width W
2
Width W
1
Width W
Bed
Path 3 Height H
3
Path 2 Height H
2
Path 1 Height H
1
Height H
0
½(H
3
+ H
2
)
½(H
2
+ H
1
)
½(H
1
+ H
0
)
Q
S
= ½V
3
(H
4
– H
2
)W
3
Q
S
= ½V
2
(H
3
– H
1
)W
2
Q
S
= ½V
1
(H
2
– H
0
)W
1
Q
S
= ½kV
1
(H
1
– H
0
)W
Bed
Q
S
= V
4
{H
S
−
½(H
4
+ H
3
)}W
4