Sensitivity Analysis for Discharge Coefficients of Piano Key Weirs

Abstract

Piano Key Weirs are relatively new weir structures that can be used as a flood release structure at the top of a dam or as a regular weir structure within a river system. The benefit of a PKW is an increased discharge capacity and, hence, lower free surface heads at the upstream reservoir. During the last few years, several experimental and numerical research investigations were carried out to analyze discharge coefficients for various PKW types. Therefore, numerical 3D CFD codes and small-scaled experimental models were used. To identify discharge coefficients, the Poleni formula can be used. By measuring the total discharge and the weir head, discharge coefficients can be calculated. However, results will be sensitive due to the weir head because basically the total energy head includes the velocity head. Hence, the position of the measuring point for the weir head and the associated velocity head must be selected carefully. To show the variation of results for discharge coefficients due to the measurement point and measurement accuracy, a sensitivity analysis for PKW discharge coefficients is given. Measurement data were collected from experimental models at Lubeck University of Applied Sciences’ Water Research Laboratory.