Thesis defense of Mikel Ezkurra Mayor

Thesis defense of Mikel Ezkurra Mayor

Title of the thesis: "Development of a numerical fluid-structure interaction methodology to model transient leakage phenomena". Obtained the SOBRESALIENTE CUM LAUDE qualification.

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• Title of the thesis: "Development of a numerical fluid-structure interaction methodology to model transient leakage phenomena.".
• Court:
  • President: Germán Castillo López (Universidad de Málaga)
  • Vocal: Davide Fugazza (Ansys)
  • Vocal: Diego Infante García (Universidad Carlos III)
  • Vocal: Iñigo Llavori Osa (Mondragon Unibertsitatea)
  • Secretary: Alain Martin Mayor (Mondragon Unibertsitatea)

Abstract

In applications that require the storage or transport of a fluid, ensuring leak-tightness is essential. The emergence of leaks can have serious consequences, both for the system and its environment. There exist critical applications which involve high pressures and temperatures, which do not permit the use of polymeric seals that are common in less demanding applications. In these critical cases, it is necessary to design seals based on metal-to-metal contact, where the geometry of the contact and the surface finish have a significant influence on leak tightness.

This dissertation presents the development of a new numerical methodology to simulate transient leak initiation and development phenomena, in systems based on metal-to-metal contact. As a result, the location and flow rate of leaks are identified, which are conditioned by both the structural part of the system and the contained fluid. For this reason, the proposed methodology is based on multiphysics models that consider fluid-structure interaction (FSI).

To determine the progression of leakage, the proposed methodology requires a criterion that must be experimentally characterised. To this end, a procedure is proposed that determines permeability as a function of contact pressures. This characterisation was performed on a system that presents uniform contact pressures, revealing that it is possible to define a leakage criterion independent of the contained fluid and the sealing force.

Finally, the developed numerical methodology was validated using a second system whose contact pressures were not uniform at closure. The results of this numerical model revealed leakage location, threshold pressure and flow rate in accordance with that observed experimentally.