Xylem SonTek FlowTracker2, User Manual

Page: 73 / 308

SonTek – a Xylem brand
FlowTracker2 User’s Manual (January 2019)
72
b) Islands (multiple channels)
i). If a river is split into multiple channels, any internal island(s) must be
accounted for in the discharge calculation,
ii). The stations at each edge of the island(s) are treated as an Island Edge,
iii). Island edge calculations are handled the same as
71 with reference to the first
component of Equation 5:1,
iv). The mean velocity at the island edge is scaled from the adjacent station by a
user defined correction factor (CF),
v). Edge water depth of zero will result in zero flow for the edge calculation.
Mean-Section Equation 5.1.2.2
The Mean-Section method is based on a measurement section that is divided into
number of stations with panels created in between adjacent stations across the section.
The average velocity of a panel is assumed to be the average velocity of the two
adjacent stations velocities in the vertical calculated from point velocity measurements
made. The equation of the Mean-Section method is given in
Equation 5:2 .
Equation 5:2 - Mean-Section Method
𝑄 = �
(
𝑏
1
− 𝑏
0
)
�
𝑑
1
+ 𝑑
0
2
� �
𝑣
1
+ 𝑣
0
2
� + ( 𝑏
2
− 𝑏
1
)
�
𝑑
2
+ 𝑑
1
2
� �
𝑣
2
+ 𝑣
1
2
� + ( 𝑏
𝑛+1
− 𝑏
𝑛
)
�
𝑑
𝑛+1
+ 𝑑
𝑛
2
� �
𝑣
𝑛+1
+ 𝑣
𝑛
2
�
Edge Open water Open Water
where,
𝑣
is the average velocity in the vertical or at the station,
d is the water depth measured at the station,
b is the location of the station.
The application of the Mean-Section equation within a measurement section is
graphically shown in
Figure 5:3 . The principle of the Mean-Section method is shown in
the figure below where panel width (W) is calculated based on the station locations
between adjacent stations across the section.