Determining accurate weir discharge-water level relationships via CFD

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Aldo Tralli, Tommaso Boschetti, Francois Clemens

Tuesday 30 june 2015

8:30 - 8:45h at Africa (level 0)

Themes: (T) Water engineering, (ST) Experimental facilities and instrumentation

Parallel session: 4F. Engineering - Instrumentation

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This study documents the use of Computational Fluid Dynamics (CFD) to obtain accurate Q(h)-relations on two weir structures in the storm protection system in the municipality of Eindhoven , in the Netherlands. Being able to accurately determine weir discharges is of key importance in urban water management: the most common method is performing a level measurement and calculating the discharge using the standard weir equation. Since this equation is only valid in certain conditions, this can lead to large deviations from the actual discharge in a real-life situation: calibrated parameters, relevant for a specific weir, would be needed, but are rarely determined because of costs and practical reasons. As a consequence, large uncertainties exist in the determination of the flow near weirs, despite the availability of measurements. CFD has been proven to correctly reproduce the water flow over a weir ([1], [2]): accurate Q(h)-relationships can be derived from the CFD calculations, providing a much better description of the actual weir discharge, than the standard equation. The CFD methodology validated in [2] against experimental data, is further documented here and applied to two different non-standard weirs: the Q(h)-relations obtained via CFD are compared with the standard equations and the discrepancies are quantified. The end goal is to implement this enhanced information to the wastewater control system of the municipality. Bibliography: 1. S. Isel , M. Dufresne , J.B. Bardiaux , M. Fischer & J. Vazquez , Urban Water Journal (2013): Computational fluid dynamics based assessment of discharge-water depth relationships for combined sewer overflows, Urban Water Journal, DOI: 10.1080/1573062X.2013.806561 2. P.van Daal-Rombouts, A.Tralli, F. Verhaart, J. Langeveld, F. Clemens, 13th IAHR/IWA International Conference on Urban Drainage(2014) : Determining accurate weir discharge-water level relationships.