A Crump weir is a standard design weir for moderate flow rates.
Note: When the downstream level of water in the river should be taken into account for backwater correction, use the crumpWeirBackwater transformation instead of the crumpWeir transformation.
Input
- headLevel: is the upstream level of water in the river measured from the top of the crest.
- type: type can be 'simple' or 'crest_tapping'. With 'crest_tapping' the pressure tapping measurements are taken and used for the flow calculation.
Coefficient set
- pUpValue: is the distance in metres from the bottom of the river, or crest, to the top of the crest.
- width: is the width if the weir crest in metres.
- sSlope: is the side slope of the weir. Crump weirs that have side slopes are uncommon, and if present only possible on one crest. The slope is the ratio of the horizontal distance over the vertical distance one metre (1m) expressed as a number.
- dischargeCoefficient: weir discharge coefficient (default is equal to sqrt(g)).
- energyHeadCorrection: if true energy head correction is taken into account (default is true).
Furthermore, one to three crests can be defined. The first crest is mandatory and only contains the relativeLevel attribute. The relativeLevels are the required head level adjustments for each crest of the weir. Each relativeLevel is subtracted from the headLevel to give a true indication of what the actual head level is over each crest. This is required as each crest at a particular weir may have different heights.
The second and third crests also must contain the width attribute. User has the choice between entering one of the following:
- singleCrest: to define only crest1
- doubleCrest: to define crest1 and crest2
- tripleCrest: to define crest1, crest2 and crest3
Output
- discharge: discharge of the weir.
Description
Calculates discharge of a triangular profile or Crump weir. The flow calculations are done using measurements taken at the weir.
The following formula is used:
Parameters:
- P = height of weir or height of vertex above bottom
- b = width of weir opening of width of triangle
- h1 = upstream water level
- H1 = upstream energy level
- h2 = downstream water level
Q = Cg . Cd . b . H1^(3/2)
Cg = sqrt(g)
Cd = 0.633
The modular limit h2/h1 = 0.75.
If this value is exceeded a missing value will be entered for the discharge. Further limiting conditions are:
P >= 0.06 m
b >= 0.30 m
h1/P <= 3
b/h1 >= 2