Numerical study of the flow over a weir : verification of widely used design rules

From antiquity to the present day, humans have attached great importance to water. Many cities are installed along the rivers. Rivers provide food and drink, facilitate transportation, and can be a source of energy. However, they are also subject to the time and the weather changes. Humans have sought to tame rivers, making their use easier and more efficient. Weirs are therefore important structures with many uses. Indeed they can be used in rivers to maintain a certain level of water upstream for navigation or to know the flow of a watercourse thanks to the theory of hydraulics. They can also be used at the head of a spillway to regulate the quantity of water contained in the reservoirs. The rules currently used for sizing weirs and calculating their flow rate - water depth ratio are based on experimental studies in the field and in the laboratory. The objective of this thesis is to use a modeling software, OpenFOAM, in order to simulate the flows on a weir and to confirm the commonly used design rules. A digital model, produced using OpenFOAM software, is used to digitize the flows with various conditions. I will first study Creager's standardized model. I will then study the influence of an approach slope on the upstream side of the weir. Finally, I will be interested in the impact of a hydraulic jump downstream of the spillway on the water flow and height. The data collected are then compared with the data usually used, which results from an in situ measurement campaign carried out by the American institute "United States Bureau of Reclamation" or USBR. This thesis confirms the relationships describing the influence of the slope for the upstream face of the weir on the one hand. On the other hand, this thesis presents a numerical method to study the influence of a hydraulic jump on the flow of a weir, with preliminary results consistent with the theory of weirs.