BNEN Master thesis: Development of a Reduced Order Model for Hydraulic Modeling of Unsaturated Soil

Title: Development of a Reduced Order Model for Hydraulic Modeling of Unsaturated Soil via MATLAB-COMSOL Livelink with Application in the Test Cover Project

1. Introduction

In the context of disposal of radioactive nuclear wastes, the typical three dimensional (3D) coupled Thermo-Hydro-Mechanical (THM) Full Order Model (FOM) remain computationally expensive due to its large spatial domain and long-term temporary scale, which severely limits its applications requiring repeated simulations, such as parametric sensitivity analysis, inverse analysis, optimization, and uncertainty quantification.

Reduced Order Model (ROM) techniques have been widely studied and successfully applied in various fields, which efficiently evaluate the system responses with significantly reduced degrees of freedom, and consequently at significantly lower computational cost while preserving both physical fidelity and solution accuracy.

Larion et al (2022) has developed ROM of coupled THM problem for saturated soil, however, since no specialized or robust solver was employed for the FOM in their studies, there remains significant potential to further reduce the offline computational cost associated with generating the optimal FOM snapshot solutions for ROM construction. Recently by using a robust FOM solver from COMSOL Multiphysics and LiveLink for MATLAB which connects the MATLAB scripting environment with COMSOL Multiphysics, we efficiently developed and used the ROM in the inverse analysis of 3D coupled THM problem.

Nasika et al (2023) developed and applied a ROM of coupled Hydro-Mechanical (HM) problem for unsaturated soils, and it would also be interesting and valuable to develop its ROM via COMSOL Multiphysics and Livelink for MATLAB.

2. Objective

As the first step of this work, this Master thesis proposal aims to develop the ROM for hydraulic problem of unsaturated soil with reference to Nasika et al (2023) and via COMSOL Multiphysics and Livelink for MATLAB. To test the efficiency and accuracy, the developed ROM will then be used in the hydraulic modeling of a large-scale mock-up of the engineered barrier system foreseen to be placed on the surface repository for low level and intermediate level short lived radioactive waste in Belgium (cAt-project, Dessel, Belgium).

3. Main References

Larion Y, Chen GJ, Zlotnik S, Díez P, Seetharam S, and Massart TJ, 2022. Using Reduced Basis Approximation for Efficient Surrogate-Based Inverse Identification of THM Parameters from an In Situ Heating Test. Rock Mechanics and Rock Engineering 55(9): 5739–5757.

Nasika C, Diez P, Gerard P, and Massart TJ, 2023. Discrete Empirical Interpolation for Hyper-Reduction of Hydro-Mechanical Problems in Groundwater Flow through Soil. International Journal for Numerical and Analytical Methods in Geomechanics 47(5): 667-693.