Edit flow measurements
Flow Measurement Data
Flow measurements can be added with 'flow measurement data' function from the 'Edit and Entry' function map. The data entered or edited will not be stored in the HYMOS database but in separate files (extension *.flw).
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Add a flow measurement by filling in the text boxes and making your selection concerning the discharge computation method and units. Enter the number of verticals and per vertical the number of measuring points. After entering all values give a filename and press <Save> to save your data.
Types of measurements
HYMOS can treat two types of flow measuring methods:
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The computational results are presented in tables and graphs. The condensed results can be stored in the database.
Mean and mid-section methods
The flow velocity is measured in verticals at distances w~i~ , i=1,m from a reference point on the river bank. The water depth at vertical i is denoted by d~i~ and the average flow velocity in that vertical by , see the underneath figure.
Figure 8.1: Definition sketch
Discharge computation
The discharge q~i~ in section i-1 to i is computed from:
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- one-point method:
- two-point method:
- three-point method:
- four-point method:
- five-point method:
- six-point method:
- profile method, see Figure
Figure 8.2: profile
The last term in the equation assumes an extrapolation of the velocity profile to the bottom according to the power profile
Air- and wet-line correction
hymosallows you to include air- and wet-line corrections in case the depths are measured with a wire, see figure.
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bf = (ce - cd) (1 - a /100)
Moving boat method
In the moving boat method the combined boat- and river velocity is measured. To compute from this the actual river velocity either the angle between the current meter and the section line or the boat velocity is measured additionally.
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The stream velocity is measured at a constant depth wd below the water surface. This velocity is transformed into the average velocity in the vertical by assuming a power law velocity profile:
with:
= average stream velocity in vertical i
c = power of power law velocity profile (5 £c £7)
d~i~ = flow depth at vertical i
wd = current meter depth
Width adjustment
Since the sum of the segment widths B c may deviate from the actual river width B m the computed segment widths are adjusted by the ratio B m /B c in the calculations.
Layout of files
The Layout of the flow measurements file (.flw) is as follows
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