Multi-component two-phase flows in conjunction with fluid-structure interaction (FSI) problems can occur in a very large variety of engineering applications; amongst them, the hypothetical severe accidents postulated in Generation IV sodium and lead fast-breeder reactors (respectively SFR and LFR).
In SFRs, the worst postulated severe accident is the so-called hypothetical core disruptive accident (HCDA), in which the partial melt of the core of the reactor interacts with the surrounding sodium and creates a high-pressure gas bubble, the expansion of which generates shock waves and is responsible of the motion of liquid sodium, thus eventually damaging internal and surrounding structures.
The LFR presents the advantage that, unlike sodium, lead does not chemically react with air and water and, therefore, is explosion-proof and fire-safe. On the one hand, this allows a steam generator inside the primary coolant. On the other hand, the so-called steam generator tube ruptures (SGTR) should be investigated to guarantee that, in the case of this hypothetical accident the structure integrity is preserved. In the first stage of a SGTR, it is supposed that the steam-generator high-pressure high-temperature water penetrates inside the primary containment, thus generating a BLEVE (boiling liquid expanding vapor explosion) with the same behavior and consequences as the high-pressure gas bubble of a HCDA.
In both HCDA and STGR, there are situations in which the multi-component two-phase flows is in low Mach number regime which, when studied with classical compressible solver, presents problems of loss of accuracy and efficiency. The purpose of this PhD is
* to design a multiphase solver, accurate and robust, to investigate HCDA STGR scenarios.
* to design a low Mach number approach for bubble expansion problem, based on the artificial compressibility method presented in the recent paper 'Beccantini et al., Computer and fluids 2024'.
The aspect FSI will be also taken into account.