Flow Calculation Rectangular Weir - Siemens Simatic RTU303xC Series Operating Instructions Manual

Program blocks
5.8 Counter and summation blocks
Parameters
Output parameters
Volumes
Error
5.8.6

Flow calculation rectangular weir

Function
The block calculates the amount of water (volume flow) flowing over a rectangular overflow
weir depending on the measured flow over height according to the formula of Poleni (see
also DIN 19557).
Q
μ
b
g
h
Figure 5-9
The formula applies only to the complete flow without influence of bottom water on the flow
amount (backwater).
The formula contains no reduction factor that takes into account influent speed, stream in
form and direction or constructions features. Note that such influences can result in
significant deviations between the calculated result and the actual flow.
306
Tag type / range of
values
Analog memory bit
configured as a float-
ing-point number:
±3.402823e-38 ..
±3.402823e+38
True / False
Flow amount [m /s]
3
Flow coefficient (without dimension without including g)
Width of the inflow [m]
Gravitational acceleration [m/s
Flow over height (water level in the head water - weir height) [m]
Formula from Poleni for flow calculation of rectangular weirs
Description
Tag in which the volume added together by the
block is output.
The volume unit at the input corresponds to the
volume unit at the output.
Overshoot or undershoot occurred.
]
2
Operating Instructions, 06/2019, C79000-G8976-C382-06
RTU303xC