Context:

Describing mathematically the hydraulic behavior in control structures leads to nonlinear coupled differential equations, which do not have analytical solution in the majority of engineering problems. However, it is possible to obtain approximate solutions from the finite volume method (FVM). This method converts a continuous medium with infinite variables into a discrete medium with established geometries and certain boundary conditions.

Methods:

Using the Ansys Fluent 17.0 software, a 1:70 scale 2D numerical model was developed without considering the effect of stacks and abutments on the weir under permanent flow conditions of the control structure and the radial gate system of the El Quimbo dam. The hydrodynamic analysis of the structure was carried out under free surface conditions and with different hydraulic loads, for openings of 704 meters above sea level, 706.9 meters above sea level, 709.4 meters above sea level, 712 meters above sea level and 724.6 meters above sea level. Subsequently, the numerical model was validated based on the comparison between the numerical results and the theoretical data made by both Ingetec and the tests in the physical model developed by the National University of Colombia in Manizales.

Results:

For a return period of 100 years, the numerical model estimated a sheet of 0.0306 m corresponding to 2,143 m in the El Quimbo structure. With this arrangement, 80.7996 Liters per second entered the control volume and 80.7324 Liters per second left, giving rise to a variation of 0.08316%. The largest water sheet variation of the numerical model with respect to the observed sheet is 3.1% (0.258 m), which corresponds to the increasing probable maximum for an opening of gates with elevation (724.6 m) and with a discharge of 290 L/s. Similarly, the higher speeds developed by the flow in the landfill originate at the exit of the deflector, corresponding to the abscissa K0 + 5,19 m. According to the numerical model, it was determined that the impact of the jet in the channel is made with a maximum speed of 6.15 m/s.

Conclusions:

The relation between the hydraulic load with respect to the design load must not exceed 1.33, which agrees with that recommended by the USBR. Also, the cavitation condition found in the fast can be considered incipient cavitation. In landfill design, the H/HD ratio directly affects the appearance of cavitation phenomena on the structure, the development of high velocities in the fast, the deflector, and the discharge capacity of the landfill.