Thermal-hydraulic Simulations and Optimization (TSO)



  • Safety analysis of nuclear energy systems, both fission and fusion systems
  • Thermal-hydraulic analysis and optimization of components in energy engineering
  • Development of models for fundamental thermal-hydraulic processes in energy engineering



The research tasks of the group Thermal-hydraulic Analysis and Optimization (TSO) are mainly devoted to the numerical simulation and optimization of thermal-hydraulic systems, one part of the R&D activities of both the Program NUSAFE and Program FUSION and belong to the research field Energy of HGF.

The research activities are devoted to innovative nuclear systems, fusion reactor (EU DEMO) and other advanced energy systems. Research focus is put mainly on the development and validation of thermal-hydraulic models and simulation codes, which are applied to reliable simulation of thermal-hydraulic processes, analysis of safety performance and optimization of advanced energy systems.


 Expertise fields

  • Detailed numerical analysis of flow and heat transfer in complex components of energy engineering with Computational Fluid Dynamics (CFD) Programs such as ANSYS-CFX, OpenFOAM;
  • Safety analysis of advanced energy systems with system thermal-hydraulics (STH) codes such as RELAP-3D, MELCOR and ATHLET;
  • Analysis and optimization of fuel elements and reactor cores with the subchannel analysis code MATRA;
  • Development, validation and qualification of numerical codes and models for various thermal-hydraulic processes and systems;
  • Education and training of students and young researchers via R&D activities, lectures, scientific seminars and international collaboration.


 Research activities


  • Contribution to the EUROfusion WPSAE Project related to EU DEMO in the pre-conceptual design phase with the following tasks:
    • Assessment of the impact of design choices on fulfillment of the safety objectives and safety criterions;
    • Deterministic analysis of the selected accident sequences and assessment of their consequences;
    • Validation of system codes RELAP5-3D and MELCOR with the experimental data of the First Wall Mock-Up (FWMU) under LOFA conditions;
    • Application of the Best-Estimate Plus Uncertainty (BEPU) method to RELAP5-3D and MELCOR;
    • Accident analysis for the HCPB-PHTS-IHTS Model with RELAP5-3D;
  • Contribution to the EUROfusion WPDIV Project: Analysis of the jet flow and the local heat transfer in the HEMJ Diverter and its optimization;
  • CFD simulation of a Small Modular Reactor (SMR);
  • Investigation on thermal-hydraulic behavior in the fuel assembly with wire wraps using the CFD approach;
  • Numerical analysis of Sodium boiling behavior;
  • CFD studies on bubble behavior under pool scrubbing conditions and the impact on the wash down of aerosols in water pool (decontamination);
  • Extension of the subchannel analysis code MATRA and participation in the OECD/NEA benchmark program CANDU-TH-1;
  • Improvement of the critical flow model for the STH code ATHLET and participation in the OECD/NEA benchmark program PKL-IBLOCA;
  • Investigation and model development of post-dryout heat transfer and rewetting at high pressure conditions.


Education activities

  • Lectures and scientific seminars (see website
  • Supervision of Bachelor and Master thesis 


   Prof. Xu Cheng

   Phone: (+49) 721 608 45356 or -22561

   E-mail: xu cheng does-not-exist.kit edu