Modelado computacional de dinámica de fluidos de flujos en aliviaderos de canal
- Autores: Lourenço Sassetti Mendes
- Directores de la Tesis: Javier López Lara (dir. tes.), Teresa Viseu (codir. tes.)
- Lectura: En la Universidad de Cantabria ( España ) en 2022
- Idioma: español
- Títulos paralelos:
- Computational Fluid Dynamics Modelling of Flows in Spillways Chutes
- Tribunal Calificador de la Tesis: Jorge Saldanha Matos (presid.), María Emilia Maza Fernández (secret.), Alessandro Romano (voc.)
- Programa de doctorado: Programa de Doctorado en Ingeniería de Costas, Hidrobiología y Gestión de Sistemas Acuáticos por la Universidad de Cantabria
- Materias:
- Enlaces
- Tesis en acceso abierto en: UCrea
- Resumen
- español
Esta tesis tiene el objetivo de evaluar y desarrollar modelos numéricos eficientes para la simulación de flujos aireados en aliviaderos, con aplicación a la investigación y a la ingeniería práctica. Utilizando el software OpenFOAM®, se ha desarrollado un modelo eficiente para flujos aireados para su uso en ingeniería. Las RANS y el método VOF se han acoplado a un modelo Sub-grid bubble population. Se ha realizado una evaluación exhaustiva de la eficacia, el coste computacional y la fiabilidad, incluso un análisis detallado de sensibilidad de los parámetros del modelo. Además, en un aireador de fondo en un aliviadero, el Two-Phase VOF se compara con el Complete Two-Phase Euler que ha demostrado eficiente en relación coste-beneficio y un valor extremo en los flujos aireados. En el final, se han demostrado las ventajas de un enfoque integrado del Two-Phase VOF con un modelo físico para evaluar dos aliviaderos en una presa real.
- español
Spillway design is key to the effective and safe operation of dams. Typically, the flow is characterized by high velocity and high turbulence levels. Furthermore, air-entrainment is common and must be considered in the design. At the prototype scale, the hydrodynamics observed in this type of structure is very complex and characterized by a two-phase air-water flow. Thus, the physical modelling is conditioned by the scale effects, especially the limitations in reproducing aeration. The numerical modelling also implies significant constrains due to the flow’s high turbulence levels and entrained air. Due to the large size of the prototype structures, it is infeasible to model individual air-bubbles. In the last two decades, advances in Computational Fluid Dynamics made available several numerical tools to aid hydraulic structures engineers. The most frequent approach is to solve the Reynolds-average Navier–Stokes equations using an Euler type model combined with the Volume-of-Fluid (VoF) method.
Three components constituted the PhD research, aiming the assessment and development of efficient numerical models for spillway chutes aerated flows in research and practical engineering.
First, using the OpenFOAM ® toolbox, an efficient model for aerated flows is developed for engineering purposes. The Two-Phase Volume-of-Fluid solver of the Reynolds-average Navier–Stokes equations is coupled with a Sub-grid bubble population model that simulates entrainment and transport. A comprehensive assessment of the effectiveness, computational cost, and reliability is performed. Local and continuum bubble entrainment are evaluated in two distinct flows: an impinging jet and along a spillway chute. A detailed sensitivity analysis of the model’s parameters is conducted. Calibration and validation are performed against experimental and prototype data. Good accuracy is found, meeting engineering standards, and the additional computation cost is marginal. Results depend primarily on the Volume-of-Fluid method ability to reproduce the interface. Calibration is straightforward in self-aeration but more difficult for local aeration.
Second, an assessment is performed in a spillway offset aerator, comparing the Two-Phase Volume-of-Fluid solver with the Complete Two-Phase Euler Reynolds-average Navier–Stokes equations solver, which is still considered to demand exorbitant computational resources. As expected, the Two-Phase Volume-of-Fluid results depend highly on the mesh, particularly the air-water interface tracking and the reproduction of air-pockets. The Complete Two-Phase Euler model exhibits the most accurate results and mesh convergence in the low-aeration. Surprisingly, intermediate mesh resolutions are sufficient to surpass the Two-Phase Volume-of-Fluid performance with reasonable calculation efforts. Moreover, compressibility, flow bulking, and several entrained air effects in the flow are comprehended. Hence, the Complete Two-Phase Euler solver demonstrated an efficient cost-benefit performance and extreme value in spillway aerated flows. Nonetheless, further developments are expected to enhance the efficiency and stability of this model.
Third, the benefits and efficiency gains of an integrated approach of the Two-Phase Volume-of-Fluid solver with a physical model to analyse the operation of a real dam spillways are demonstrated.Even in aerated flows, the differences between the models are not so expressive, allowing the Two-Phase Volume-of-Fluid to provide insights, optimizing the construction and operation of the physical model, and to be calibrated and validated with laboratory data.
- español
