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Measurement of discharge in open channels is one of the main concerns in hydraulic engineering. The structures used for this aim should be accurate, economical and easy to use. Weirs are among the oldest and most convenient hydraulic structures that have been used in both laboratory and field for flow measurement in open channels. Due to limitations of simple sharp crested weirs, recently compound sharp crested weirs have attracted great attention of civil engineers. In general, use of compound sharp crested weirs can be an appropriate solution when the discharge should be measure accurately with a reasonable sensitivity over a wide range of flows. The aim of this research is three-dimensional simulation of flow on contracted compound arched rectangular sharp crested weirs by using FLUENT software. For multiphase flow simulation, VOF method is used and for simulation of turbulent flow, RNG k-ɛ turbulence model is used and the result of numerical model is compared with experimental data. The results of this study indicate that FLUENT simulate flow on contracted compound arched rectangular sharp crested weirs with high accuracy and we can use this software for determine the discharge coefficient on contracted compound weirs.