Student Jobs

The Institut offers several opportinuties for student jobs.
Besides the jobs listed below, we are always interested in students with practical expericence for laboratory.

HiWi
2025

Large scale simulations of cemented sand samples using the finite cell method

(Gorji et al., 2023)

Cemented sands are important in soil mechanics and geotechnical applications. They consist of sand particles (Hamburger sand), embedded in a cement matrix (Portland cement mixed with water). Samples with different saturation degrees have been loaded under uniaxial compression, where experiments have been performed at the Laboratoire 3SR, Grenoble, France. The micromechanical behaviour is very complex and depends on the saturation degree 0 < S < 100%. Therefore, numerical simulations should be performed, in order to investigate the micromechanical effects and also predict fracture.

The geometries of the samples are very complex and irregular, and thus are described by computed tomography (CT) scans. In order to numerically model and simulate these structures in an automated fashion, we utilize the finite cell method (FCM) as a novel discretization method. In contrast to the finite element method (FEM), it used a simple Cartesian grid as a mesh, which is decoupled from the geometry. We also employ extensions to improve the FCM for composites, as described in [1]. At larger loads, fracture due to micro-cracks occurs, which we simulate using phase-field modeling [2]. The methods are implemented in our in-house C++ FCM code AdhoC++. Since these large problems require very high computing power, we use AdhoC++ together with Trilinos to perform hybrid MPI/OpenMP parallelization (MPI to distribute the simulations on multiple computers, OpenMP to use all cores of each computer) [3]. The simulations are carried out on supercomputers of the Zuse Institute Berlin (ZIB), National High Performance Computing (Nationales Hochleistungsrechnen – NHR) [4], or on the high-performance computer (HPC) cluster of the TUHH [5].

 

Tasks:

  • Support in performing linear elastic and phase-field simulations of cemented sand samples under uniaxial compression

  • Performing FCM simulations using our in-house C++ code AdhoC++ with Trilinos for hybrid MPI/OpenMP parallelization

  • Simulation of different samples

  • Post-processing of the results with ParaView [6]

  • Interpretation of the results and discussion with the supervisor

  • Cooperation with project partners (M.Sc. Elnaz Hadjiloo, elnaz.hadjiloo(at)tuhh.de)

  • Optional: Comparison with FEM results and experiments

 

Required skills:

  • Strong background in mathematics (partial differential equations) and mechanics (linear elasticity)

  • Solid background in the finite element method (FEM)

  • Good programming skills (experience with AdhoC++ & Trilinos is a plus)

  • Optional: Phase-field modeling for brittle fracture

  • Optional: Parallelization (OpenMP, MPI)

 

Ideally, you can start soon, with a duration of 3 months at up to 55 hours per month.

If you’re interested please contact M.Sc. Mahan Gorji (mahan.gorji(at)tuhh.de).

 

References

[1] M. Gorji, M. Komodromos, W. Garhuom, J. Grabe, and A. Düster. Geometry smoothing and local enrichment of the finite cell method with application to cemented granular materials. Computational Mechanics, 75:429–454, 2025.

[2] S. Nagaraja, M. Elhaddad, M. Ambati, S. Kollmannsberger, L. Lorenzis, and E. Rank. Phase-field modeling of brittle fracture with multi-level hp-fem and the finite cell method. Comput. Mech., 63(6):1283–1300, 2019.

[3] J. N. Jomo, F. de Prenter, M. Elhaddad, D. D’Angella, C.V. Verhoosel, S. Kollmannsberger, J.S. Kirschke, V. Nübel, E.H. van Brummelen, and E. Rank. Robust and parallel scalable iterative solutions for large-scale finite cell analyses. Finite Elements in Analysis and Design, 163:14–30, 2019.

[4] https://nhr.zib.de/en/

[5] https://www.tuhh.de/rzt/en/services/hpc

[6] https://www.paraview.org/