Full-width sharp-edged broad-crested rectangular weirs in the range 0.1 < h/L ≤ 0.3 situated in rectangular channels are frequently used in submerged flow conditions. To determine the discharge for the submerged flow, submergence coefficient and modular limit shall be known. This article deals with their determination upon a theoretic derivation and experimental research. The equation for modular limit has been determined from energy balance with simplifications. To validate it, extensive experimental research was carried out. However, the derived equation is too complicated for practical use which is why it was approximated by a simple equation applicable for the limited range. The equation for submergence coefficient was derived by modifying Villemonte’s application of the principle of superposition and its coefficients were determined using the data from experimental research of many authors. The new system of equations computes the discharge more accurately than other authors’ equations, with the error of approximately ±10% in full range of the measured data.

Ve vodohospodářské praxi se často využívají přelivy se širokou korunou, u kterých není použito přítokové koryto, ale přítoková šachta. V případě přítokové šachty není známý vliv rychlostní výšky na kapacitu přelivu, zvláště pak při různých výškách příčného profilu šachty. Dále pak není známý průběh hladiny nad šachtou a korunou přelivu a jeho relativní vyjádření. Článek popisuje experiment se svislou přítokovou šachtou, na základě kterého byl průběh hladiny nad šachtou a korunou přelivu v relativním vyjádření stanoven.

In the case of flow over rectangular broad-crested weir, where the inflow is realized by approach shaft, occurs influence of water surface level by approach flow velocity. The paper describes numerical model of flow including weir, approach and outlet shaft. Simulations of flow were created by 2D and 3D model with using three methods of turbulent modelling. In this paper a water surface level for each model setup is evaluated and then it is compared with measured values.