Team advisors :Anne GADEKE &Tamas

KRAMER

Team leader :Ricardo SANTAELLA

February 2011February 2011

Weir characteristics and equations

Mike11 formulationsType of Weirs and equationsSensitivity of coefficients

ISIS formulations

Type of Weirs and equationsSensitivity of coefficients

Comparison of results: Mike11 vs. ISIS

Conclusions

Presentation OutlinePresentation Outline

Weir CharacteristicsWeir CharacteristicsBroad-crested weirs

Transversal structures to the flow

Control of donwstream water level

Flow over the structure

Critical conditions induced

Low velocities upstream, flow acceleration downstream.

Hydraulic discontinuity (Freeflow)

Critical energy – Critical depthDirect relation Discharge ->

Depth

Weir EquationsWeir Equations

Mike11 Weir FormulationMike11 Weir Formulation

Under this formulation:C1= (1.2 – 1.705)

Broad-crested Honma Formula

Mike11 Sensitivity analysisMike11 Sensitivity analysis

ISIS Weir FormulationISIS Weir Formulation

Free-flow condition

Drowned condition

Under this formulation:

Cv Cd= (0.7 – 0.95)

Under this formulation:

Cv Cd= (0.7 – 0.95)

ISIS Sensitivity analysisISIS Sensitivity analysis

Comparison Mike11 vs ISISComparison Mike11 vs ISIS

ConclusionsConclusions Every software defines weirs equations using specific formulas/coefficients.

The theory behind weir behavior is the same (Energy equation – critical conditions), thus coefficients are related between them.

Under free-flow conditions, changes in the weir coefficients influence only conditions upstream the structure.

In general a higher coefficient defines a more effective weir, therefore smaller water level to convey a given discharge.

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