Modeling the hydraulic performance of the aeration system in dam bottom outlets using the particle finite element method

Dam bottom are key elements to control the water surface elevation below the spillway crest level. As a consequence, they are essential in reservoir management, and play a vital role in dam safety. The convenience of installing an aeration system in dam bottom outlets is well known nowadays. Otherwise, damages due to cavitation and vibration are frequently serious, as could be observed in several dams built in the beginning of the 20th century. The intrinsic features of the phenomenon make it hard to analyze either in situ or in full scaled experimental facilities. As a consequence, most of the previous studies have been carried out in small-scale physical models. The results of these works have been used to develop empirical formulas which provide an estimation of the maximum air demand of the aeration system. The progress in the development of numerical methods allows addressing this problem using numerical modeling. The Particle Finite Element Method (PFEM) had been previously applied and validated for the analysis of the performance of other hydraulic structures. In this work, it has been used to simulate air-water interaction in free-flowing gated conduits. The objective is to avoid the scale effects of physical modeling and to study in detail the key parameters. The results clarify the behaviour of the involved fluids (air and water) and provide information about the influence of the main variables that affect their circulation. (C) 2011 CIMNE (Universitat Politecnica de Catalunya). Published by Elsevier Espana, S.L. All rights reserved.