Ricerca CERCA

RANS simulations of forced convection to a liquid metal flowing in a non-uniformly heated tube


Reference persons LAURA SAVOLDI

External reference persons Prof. Luca Marocco (PoliMi)
Ing. Rosa Difonzo (PoliTo)

Research Groups MAHTEP

Thesis type RESEARCH

Description For numerical simulation of nuclear engineering applications, such as rod bundles or gyrotrons, a RANS approach is predominantly adopted. At present, a variety of turbulence models are present in the literature and implemented in fluid dynamic calculation codes. There is no universal turbulence model that provides the most accurate results regardless of the application. For this reason, it is appropriate to evaluate which model to use, through proper validation and comparison with experimental data or numerical data obtained through LES or DNS simulations. In this regard, it is good practice to adopt accepted standards to quantify the degree of accuracy inferred from the comparison of a numerical solution and the available reference data.
Liquid metals are excellent cooling fluids, adopted in both nuclear and solar thermodynamic applications. Given the difficulty of experimental investigations of liquid metals, it would be advantageous to replace them with numerical simulations. These must be able to span a wide range of Reynolds numbers in addition to providing sufficiently accurate results with an acceptable computational cost. Therefore the Reynolds-Averaged Navier Stokes (RANS) approach is preferred over more time consuming LES/DNS simulations.
In this thesis the candidate will perform RANS simulations of the turbulent forced convection to a liquid metal flowing in a uniformly and non-uniformly heated tube. Both the heat transfer in the fluid as well as in the solid wall (Conjugate Heat Transfer - CHT) will be considered. The geometry is the same as the test section used by [1], for which accurate experimental data are available for a comparison. Moreover, the RANS results will be also compared with available accurate LES data. Different turbulence models should be investigated through simulations done with OpenFOAM. The models not already available within the distribution should be first implemented. The model error will be estimated according to the ASME V&V 20-2009 Standard [2].
The expected tasks for the thesis are:
- Implementation of the Lag EB k-eps and Lag EB k-omega turbulence models in OpenFOAM;
- RANS simulations at different Reynolds numbers and heat flux boundary conditions with OpenFOAM;
- Model error analysis according to ASME V&V 20-2009 Standard.

[1] T. Laube et al. "Turbulent heat transfer in a liquid metal tube flow with azimuthally inhomogeneous heat flux", Int. J. Heat Mass Transf., 189 (2022), p. 122734
[2] ASME V&V 20-2009 (R2016), "Standard for Verification and Validation in Computational Fluid Dynamics and Heat Transfer", ASME, New York

See also  proposta_tesi_luca_marocco3.pdf 

Required skills Basic knowledge of CFD. Prior experience with OpenFOAM, Linux and C++ is a plus.

Deadline 20/06/2023      PROPONI LA TUA CANDIDATURA

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