The paper deals with the determination of the basic characteristics of flow at the crest of a rectangular broad-crested weir and in detail with the characteristics of flow separation at the upstream edge of the weir crest. The determination of the characteristics is made on the basis of measurement of the water surface level, the pressure head and the velocity field using the Particle Image Velocimetry method. The characteristics are expressed dimensionless in relation to the energy overflow head and the critical depth.

Abstract. The article describes the processing of specific junior research FAST-J-11-51/1456 which dealt with physical and CFD of the velocity field during the flow around of bridge piers. Physical modelling has been carried out in Laboratory of water management research in Institute of Water Structures in Brno University of Technology -Faculty of Civil Engineering. To measure of the velocity field in profile of bridge piers were used laser measuring method PIV (Particle Image Velocimetry). The results of PIV served as a basis for comparing experimental data with CFD results of this type of flow in the commercial software ANSYS CFX.

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