Most large dams are designed with complex geometry in which physical models have been widely used. The overflow design guidelines were used for standard geometries, which are quite simple. For more complex geometries, the physical and numerical models studied here have proven useful. The disadvantages of physical models are high costs and the time required to obtain results. In this paper, we used a numerical method called volume of fluid (VOF) to calculate flow rates over three types of ogee weirs. The results were compared and these comparisons showed a good proximity between the numerical and experimental data. The results provided information on the accuracy with which a commercially available CFD computational fluid dynamics model can predict spillway flow. An Ogee-shaped spillway was used to control the height and volume of the water behind the dam. The geometric properties affecting the hydraulic variables were studied. The most common hydraulic overflow structure was analyzed to consider its optimal safety, operating and maintenance costs. Based on the analysis, geometry, flow rate, and construction cost were sensitive and affected the hydraulic properties of the system. A digital volume of fluid (VOF) method was considered for computational analysis of geometric and hydraulic variables for three types of spillways. The numerical results were compared to the experimental observations and the measurements made it possible to verify the performance of the model and the coding. The comparison showed that the numerical modeling was improved and accurately predicted the multi-variables and objective functions involved in the complex operation of a hydraulic structure. Keywords: Weir shape, numerical method, fluid volume, fl...... middle of paper ......stem. The authors considered this topic as an important topic of critical flow conditions in the analysis and design of water resources systems. The importance of technical implementation and maintenance is taken into account. Types of Weirs Used in This Study In this study, three types of weirs were used. Type I has a low bend radius, Type II has a medium bend radius, and Type III has a high bend radius. Three types of weirs are selected to study the effects of geometry on discharge rates. In 2001, Savege & Johnson worked numerically and experimentally on type II and in this case their results are used [9]. Type I has a small bend radius and requires fewer materials. So type II cheaper than the others. But type II has high curvature, requires more materials and will be the most expensive. In Table 1, three types of weirs and their design height (Hd) are presented.