May a Standard VOF Numerical Simulation Adequately Complete Spillway Laboratory Measurements in an Operational Context? The Case of Sa Stria Dam

Maria Grazia Badas,Michela Garau,Riccardo Rossi

doi:10.3390/w12061606

Abstract

The present work aims to assess whether a standard numerical simulation (RANS-VOF model with k − ϵ closure) can adequately model experimental measurements obtained in a dam physical model. The investigation is carried out on the Sa Stria Dam, a roller compacted concrete gravity dam currently under construction in Southern Sardinia (Italy). The original project, for which a physical model was simulated, included a downstream secondary dam. However, due to both economic and technical reasons, the secondary dam may not be built. Hence, it is important to assess the flood discharge routing and energy dissipation in the modified plan. Numerical validation is performed adopting the same laboratory configuration, in presence of the downstream dam, and results show a good agreement with mean experimental variables (i.e., pressure, water level). An alternative configuration without the downstream dam is here numerically tested to understand the conditions of flood discharge and assess whether its results can give relevant information for the design of mitigation measures. The topic is of interest also from a more general perspective. Indeed, the feasibility to integrate numerical models with existing laboratory measurements can be very useful not only for new constructions but also for existing dams, which may need either maintenance or upgrading works, such as in case of flood discharge increment.

Highlights

The design and safety assessment of the discharge structures of dams have always relied upon physical models, which are still irreplaceable for evaluating overflow discharge and flood energy downstream dissipation
The multiphase flow of air and water over the spillway and along the terrain downstream of the dam is modelled in the framework of unstructured finite-volume schemes with the help of the public-domain computational fluid dynamics (CFD) code OpenFOAM R and using Reynolds-Averaged Navier–Stokes (RANS) models to account for the turbulent nature of the flow and the volume of fluid (VOF) method to model the evolution of the air/water interface
The model is applied to the configuration without the downstream dam (Section 4.2), and the analysis is extended from the Sa Stria Dam to the flow along the riverbed

Summary

Introduction

The design and safety assessment of the discharge structures of dams have always relied upon physical models, which are still irreplaceable for evaluating overflow discharge and flood energy downstream dissipation. One of the first examples of numerical simulation applied to dam modelling was by [1] who computed the flow over a spillway with a 3D RANS (Reynolds Averaged Navier Stokes)model. Many studies have been devoted to both the development and testing of numerical models in this context (see the review article by [2] and references therein). Parallel to these methodological works, investigations on case studies are important to understand the feasibility to apply numerical methods to a field traditionally investigated only with physical modelling.

Methods

Results

Conclusion