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@PHDTHESIS{Mller:960707,
      author       = {Müller, Henrik},
      othercontributors = {Allelein, Hans-Josef and Kneer, Reinhold and Laurien,
                          Eckart},
      title        = {{D}evelopment of a multivariate wall function approach for
                      momentum, heat and mass transfer in the wall condensation
                      regime},
      school       = {Rheinisch-Westfälische Technische Hochschule Aachen},
      type         = {Dissertation},
      address      = {Aachen},
      publisher    = {RWTH Aachen University},
      reportid     = {RWTH-2023-06349},
      pages        = {1 Online-Ressource : Illustrationen, Diagramme},
      year         = {2022},
      note         = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
                      University 2023; Dissertation, Rheinisch-Westfälische
                      Technische Hochschule Aachen, 2022},
      abstract     = {The use of numerical methods for the safety analysis of
                      nuclear power plants helps suppliers, operators and safety
                      authorities to justify the plant layout, understand the
                      plant behavior in different accident scenarios, to define
                      accident mitigation measures and to identify potentials for
                      the improvement of the plant safety. Complementary to the
                      well-established lumped parameter or system codes, there is
                      an increasing demand to use computational fluid dynamics
                      (CFD) codes for this task. CFD codes offer the ability to
                      gain additional insights into, for example, localized or
                      three-dimensional flow phenomena in the course of an
                      accident, especially the distribution of hydrogen and the
                      formation of combustible mixtures. One application of great
                      interest for the use of CFD-codes is the containment flow
                      during a loss of coolant accident (LOCA). Due to the
                      presence of phenomena such as wall condensation, the
                      analysis of the containment flow during a LOCA requires a
                      fine mesh resolution at the wall surface to accurately
                      predict the flow. However, with such a fine mesh, the
                      calculations require a prohibitive large amount of
                      computation time. Therefore, subgrid models, so called wall
                      functions, need to be employed to reduce the required grid
                      resolution and thus the computational time. Currently
                      available wall functions are not suitable for modeling
                      containment flows under LOCA conditions. In particular, they
                      do not include the effects of buoyancy and
                      condensation-induced wall normal velocity, commonly referred
                      to as the suction effect. The wall function approach
                      presented in this thesis consists of a set of empirical
                      functions based on experimental data supplemented by high
                      resolution numerical data. In addition to the effects
                      typically encountered in wall functions, the approach
                      includes the influence of buoyancy and wall normal flow. To
                      account for these effects, a covering set of non-dimensional
                      parameters is derived and the input data are combined into
                      multivariate algebraic functions using the concept of radial
                      basis functions. This allows an easy and computationally
                      fast integration of the wall function into different CFD
                      codes. An exemplary implementation in the CFD code ANSYS CFX
                      is presented. A first validation is performed based on
                      separate and integral effect tests. The separate effect test
                      validation demonstrates that the newly developed wall
                      function approach provides improved results compared to a
                      standard wall function, especially under containment-like
                      flow conditions. However, larger scale integral effect tests
                      do not show such improvement due to the limited application
                      range of the new model resulting from the limited amount of
                      available input data. Nevertheless, the results show that
                      the newly developed wall function approach has the potential
                      to enable computationally affordable CFD calculations of a
                      full containment under LOCA conditions with an accurate
                      prediction of the near wall momentum, heat and mass
                      transfer, although some work remains to be done.},
      cin          = {413110},
      ddc          = {620},
      cid          = {$I:(DE-82)413110_20140620$},
      pnm          = {BMWI-1501489 - Experimente und CFD-Modellentwicklung zu
                      Wandkondensationsvorgängen im Sicherheitseinschluss
                      (BMWI-1501489)},
      pid          = {G:(DE-82)BMWI-1501489},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.18154/RWTH-2023-06349},
      url          = {https://publications.rwth-aachen.de/record/960707},
}