Doctoral School

Reading date: 14/01/2026

• RODRÍGUEZ ROMERO, CARLOS EDUARDO: Analysis of coupled hydro-mechanical processes in double-structure geomaterials for nuclear waste storage
  
  Author: RODRÍGUEZ ROMERO, CARLOS EDUARDO
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN GEOTECHNICAL ENGINEERING
  Department: Department of Civil and Environmental Engineering (DECA)
  Mode: Normal
  Deposit date: 04/12/2025
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: VAUNAT, JEAN | GENS SOLE, ANTONIO
  Thesis abstract: The safe long-term isolation of high-level radioactive waste requires engineered barriers capable of maintaining low permeability and mechanical stability under complex thermo-hydro-mechanical (THM) conditions. Among candidate materials, compacted bentonite exhibits a distinctive double-structure behaviour, governed by the coexistence of micro- and macro-porous domains. This thesis focuses on the analysis of coupled hydro-mechanical processes in double-structure geomaterials, with particular attention to bentonite mixtures of blocks and pellets, as used in buffer systems for deep geological repositories. The research first reviews the geomechanical basis of double-structure soils and identifies the experimental evidence supporting their dual-porosity nature. A constitutive THM framework is then developed, extending the existing double-structure formulation to incorporate: (i) the parameter ακ to control microstructural deformation; (ii) a fabric-dependent structuration law to represent the memory and degradation of compression; and (iii) frictional resistance at block–pellet and block–wall interfaces.The model was implemented and calibrated using laboratory and mock-up experiments from the BEACON project, including the MGR22, MGR23, and MGR27 experiments, the EPFL path-dependent tests and the POSIVA test. Numerical simulations successfully reproduced the evolution of swelling pressure, void ratio, dry density, water content and water intake observed experimentally. The results confirmed that friction plays a decisive role in the redistribution of stresses between pellets and blocks, while microstructural evolution governs the long-term homogenisation process. The enhanced formulation captured partial density homogenisation and the persistence of microstructural porosity, in agreement with laboratory observations.Overall, the thesis provides an improved understanding of the coupled hydro-mechanical behaviour of double-structure bentonites and proposes a robust constitutive framework capable of reproducing their key features under repository-relevant conditions. The work highlights the necessity of considering both microstructural evolution and frictional effects in predictive models for bentonite barriers, thus contributing to the reliability of long-term safety assessments of deep geological repositories.
  

Reading date: 15/01/2026

• DEHGHANSOURAKI, DANIAL: Modeling Sediment Transport in Rivers and Reservoirs using an Accelerated Model
  
  Author: DEHGHANSOURAKI, DANIAL
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN CIVIL ENGINEERING
  Department: Department of Civil and Environmental Engineering (DECA)
  Mode: Article-based thesis
  Deposit date: 04/12/2025
  Reading date: 15/01/2026
  Reading time: 12:00
  Reading place: ETSECCPB Edificio C2 -212 - Sala Conferencias Campus Nord Barcelona
  Thesis director: BLADE CASTELLET, ERNEST | LARESE DE TETTO, ANTONIA
  Thesis abstract: Reservoir sedimentation is a critical, ongoing issue in managing water resources sustainably. While conventional two-dimensional models are computationally efficient, they miss key three-dimensional processes, such as thermal stratification. Three-dimensional models provide a more accurate physical representation but require extensive computational resources, making them impractical for large-scale applications. This research creates a computational framework that combines High-Performance Computing, Artificial Intelligence, and advanced 3D multiphysics simulation to bridge this gap.A two-dimensional hydro-morphodynamic model (R-Iber) was rebuilt for Graphics Processing Units, resulting in computational speed-ups of one to two orders of magnitude. The accelerated model supported training a Deep Neural Network surrogate, enabling a 100,000-run Monte Carlo analysis for robust model calibration and uncertainty quantification. In parallel, a comprehensive three-dimensional multiphysics model was developed in the Kratos framework to simulate the 3D fluid-thermal problem.The integrated approach was used for the Riba-roja reservoir system. It measured how thermal stratification affects sediment trapping efficiency. Results show that combining HPC, AI, and multiphysics modeling leads to practical and actionable methods for sustainable reservoir management.
  

• GIESEN LEÓN, JEREMY JENS: Modeling and Optimization of Timing Interference for Time Critical Systems on Multicore COTS Platforms
  
  Author: GIESEN LEÓN, JEREMY JENS
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN COMPUTER ARCHITECTURE
  Department: Department of Computer Architecture (DAC)
  Mode: Normal
  Deposit date: 27/11/2025
  Reading date: 15/01/2026
  Reading time: 11:00
  Reading place: C6-E101
  Thesis director: MEZZETTI, ENRICO | CAZORLA ALMEIDA, FRANCISCO JAVIER
  Thesis abstract: Critical Real-Time Embedded Systems (CRTES) underpin automotive, aerospace, medical devices, among others. They must guarantee deterministic, certifiable behavior under worst-case conditions. As functionality grows (sensor fusion, AI, etc), uniprocessors fall short, prompting adoption of COTS multicores. Yet shared resources induce timing interference that threatens predictability and complicates certification, especially in heterogeneous SoCs with crossbars, bridges, and hierarchical memory.This Thesis advances timing predictability on complex multicores through three linked pillars: standardized hardware observability, contention modeling, and system-level optimization. Together they form a coherent, auditable path from low-level measurements to design decisions.First, we introduce unified observability frameworks combining core-local counters with system-level tracing. They correlate hardware events with task phases, reconstruct scheduling and contention across cores and interconnects, and standardize configuration and interpretation across heterogeneous devices. Measurements are attributed to tasks (excluding OS activity), incur bounded overhead, and yield ordered access sequences preserving temporal structure. Along with latency tables for memories and bridges, these artifacts make timing phenomena measurable and calibrate conservative models.Second, we develop contention models grounded in realistic traces. Traditional Access-Count Contention Techniques (ACCT) are overly conservative for parallel crossbars. Sequence-Aware Techniques (SACT) exploit request ordering to prune infeasible overlaps and tighten bounds. We propose ASCOM, a scalable framework balancing accuracy through compositional pairing against contender sequences and segmentation of long traces. We derive explicit upper/lower bounds to quantify margins and add bridge awareness to capture inter-cluster traversals and remote-memory asymmetries. Across single- and multi-crossbar SoCs, sequence-aware analysis yields tighter, trustworthy bounds while remaining tractable on industrial-scale traces.Third, we examine how modeling informs code and data placement across heterogeneous memories. Feasibility considers capacity and compatibility; locality and non-uniform latencies are captured through calibrated SACT. Exploration reveals pronounced sensitivity to placement: with identical workloads and schedules, changing only the mapping can shift contention by over 100% of reference execution time, due to bridge traversals, device asymmetries, and port effects. Architectural factors thus directly shape worst-case interference, elevating placement to a first-order design parameter.An end-to-end workflow operationalizes these ideas. System-level traces are captured on an industrial target hardware. Traces are filtered into ordered access sequences retaining temporal structure and feeding SACT analysis. Empirical campaigns build latency tables for memories and bridges. With these calibrated inputs, the bridge-aware SACT model estimates contention and total delay for alternative placements.Results show robust contention analysis on COTS multicores is feasible when: (i) the right signals are observed with standardized, low-intrusion instrumentation; (ii) models are sequence- and bridge-aware with explicit margins; and (iii) insights drive placement where locality and capacity are addressed coherently. Because ordered sequences, latency tables, and task-scoped metrics come from the deployed hardware, conclusions are auditable and fit safety cases. Combining hardware-aware instrumentation, realistic modeling, and contention-driven mapping, the Thesis provides a practical framework for timing predictability in CRTES and narrows the gap between certification expectations: traceability, explainability, repeatability and the behavior of parallel interconnects and heterogeneous memories in contemporary multicore SoCs.
  

• SAYAD NOGHRETAB, BABAK: HYDRO-MECHANICAL MODELING OF GAS FLOW THROUGH CLAY-BASED ENGINEERED ISOLATION BARRIERS
  
  Author: SAYAD NOGHRETAB, BABAK
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN GEOTECHNICAL ENGINEERING
  Department: Department of Civil and Environmental Engineering (DECA)
  Mode: Normal
  Deposit date: 16/10/2025
  Reading date: 15/01/2026
  Reading time: 10:00
  Reading place: ETSECCPB.UPC, Campus NordBuilding C1. Classroom: 002C/Jordi Girona, 1-308034 Barcelona
  Thesis director: PUIG DAMIANS, IVAN | OLIVELLA PASTALLE, SEBASTIAN
  Thesis abstract: Safe management of high-level radioactive waste (HLRW) requires durable isolation from the biosphere over geologic time. Deep geological repositories (DGRs) rely on engineered and natural barriers, with bentonite as a key buffer and backfill material because it seals fractures, sorbs radionuclides, and develops swelling pressure during hydration. During operation and early post closure, resaturation and corrosion generate gas, so predicting system behavior requires coupled hydro gas mechanical models that represent double porosity, heterogeneity, and preferential pathways. This Thesis addresses that need by integrating explicit pathway mechanics in compacted buffers, double porosity constitutive laws for pellet/powder mixtures, and image-based statistics linked to finite element simulations in CODE_BRIGHT.First, a three-dimensional coupled hydro gas mechanical model of the large-scale gas injection test (LASGIT) is formulated with heterogeneous initial permeability, embedded fractures with dilatancy, and explicit gap closure states at the canister–buffer interface and is exercised through targeted sensitivity analyses. Second, the BENTOGAZ laboratory mixture of equal parts pellets and MX-80 powder is modeled with the Barcelona Expansive Model to couple microstructure and macrostructure; systematic parameter studies are complemented by a handmade heterogeneity setup that assigns distinct properties to randomly distributed pellet and powder domains. Third, an image to model workflow for SEALEX links micro-CT analysis to simulation: binarized slices yield macroporosity maps, directional variograms quantify anisotropy and correlation lengths, and the fitted statistics generate anisotropic porosity fields that enable automatic heterogeneity on the finite element mesh.Together, these methodologies constitute a set of methods that couple explicit fractures with dilatancy, dual structure behavior, and image informed spatial heterogeneity for repository relevant assessment of gas entry, resaturation, and sealing performance.
  

Reading date: 16/01/2026

• LU, YONGGANG: Research on Transient Flow Characteristics and Dynamic Behaviour of hydraulic Pumps in Support of Energy transition
  
  Author: LU, YONGGANG
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN MECHANICAL, FLUIDS AND AEROSPACE ENGINEERING
  Department: Department of Mechanical Engineering (EM)
  Mode: Article-based thesis
  Deposit date: 26/11/2025
  Reading date: 16/01/2026
  Reading time: 11:00
  Reading place: Aula I 28.8 Laboratori Hidràulica, Pavelló D, planta -1, ETSEIB
  Thesis director: PRESAS BATLLÓ, ALEXANDRE
  Thesis abstract: Amid the global shift to low-carbon energy, multi-energy complementary power systems are key to achieving carbon neutrality. Nuclear energy, pumped storage hydropower, and industrial waste energy recovery enhance energy system flexibility but increase demands on energy transfer and fluid transport. Hydraulic pumps, vital for energy conversion, face challenges: RCPs in Generation IV lead-cooled reactors suffer from corrosion and vibration; pumped storage units face stability issues; and industrial waste pressure recovery is inefficient under variable conditions. This study focuses on three core devices—RCPs, pump-turbines, and PATs—using analysis, simulation, and experiments to investigate their dynamics and propose optimizations.First, the transient fluid-structure interaction of lead-bismuth eutectic RCPs during startup was studied. A mathematical model for flow rate and rotational speed under various startup modes was developed. Bidirectional fluid-structure interaction analysis showed maximum stress at the impeller blade root and maximum deformation at the blade-hub/shroud junction. Higher startup torque increased acceleration and torsional shock, with peak stress linked to instantaneous rotational speed. These findings inform safer RCP startup design.Second, the dynamic characteristics of reversible pump-turbines under load rejection were studied using 3D transient simulations and entropy production theory to analyze energy loss. The study found the unit crosses the S-shaped region during load rejection, with complex flow under reverse pump conditions. When speed exceeded 110%, significant fluctuations in axial hydraulic thrust and torque were observed, and blade pressure loads became asymmetric. These findings improve understanding of pump-turbine transient behavior.Finally, a two-stage PAT system for high-pressure energy recovery in petrochemicals was studied, focusing on vortex evolution and pressure pulsations. Pulsations in the diffuser stemmed from rotor-stator interaction near the tongue, with strong inter-stage interference at the inlet impeller. Low-frequency pulsations from vortex shedding were detected at high flow rates, threatening system stability. Combined experiments and simulations clarified pulsation propagation, aiding inter-stage matching and efficiency improvements.The innovative results of this study have been published in leading fluid mechanics and energy journals. They advance the theoretical understanding of hydraulic pump dynamics and provide practical solutions for nuclear safety, grid flexibility, and industrial energy conservation. The main body of the dissertation details each research component, with three supporting JCR Q1 articles appended.