Air demand estimation in bottom outlets with the particle finite element method

Abstract

Dam bottom outlets play a vital role in dam operation and safety, as they allow controlling the water surface elevation below the spillway level. For partial openings, water flows under the gate lip at high velocity and drags the air downstream of the gate, which may cause damages due to cavitation and vibration. The convenience of installing air vents in dam bottom outlets is well known by practitioners. The design of this element depends basically on the maximum air flow through the air vent, which in turn is a function of the specific geometry and the boundary conditions. The intrinsic features of this phenomenon makes it hard to analyse either on site or in full scaled experimental facilities. As a consequence, empirical formulas are frequently employed, which offer a conservative estimate of the maximum air flow. In this work, the particle finite element method was used to model the air-water interaction in Susqueda Dam bottom outlet, with different gate openings. Specific enhancements of the formulation were developed to consider air-water interaction. The results were analysed as compared to the conventional design criteria and to information gathered on site during the gate operation tests. This analysis suggests B Fernando Salazar that numerical modelling with the PFEM can be helpful for the design of this kind of hydraulic works.

A State of the Art Review of the Particle Finite Element Method (PFEM)

“…The first works in this area [62,64,65] used a hybrid FEM-Eulerian approach to simulate overtopping and failure of rockfill dam and the related seepage phenomena. Salazar et al [118] studied a real dam geometry and modelled the 3D air-water interaction to estimate the air demand at the bottom outlets. On the other hand [119] focused on the water shock-waves that form at the exit of dam spillways.…”

Hydrodynamic Performance and Cavitation Analysis in Bottom Outlets of Dam Using CFD Modelling

“…Bottom outlets are utilized as one of the dam's hydraulic structures to control the reservoir impoundment, the reservoir evacuation in case of emergency, and the removal of the sediments entering the reservoir. Hence, they require careful design and harmful factors identification [1]. On the other hand, to ensure the channel's proper operation, its associated hydraulic and hydromechanical installations, including gates and valves, the flow discharge capacity should be carefully examined along with performing hydraulic model tests [2].…”

Shockwaves in spillways with the particle finite element method

“…PFEM has also been previously applied to solving 3-dimensional free-surface flows, particularly in hydraulic structures [10]. It has also been employed to estimate air flow demand in bottom outlets [28], [20]. This paper explores the possibilities of using PFEM in full-scale hydrodynamic analysis of spillways with geometric irregularities that generate shockwaves.…”