A grid convergence index study of mesh style effect on the accuracy of the numerical results for an indoor airflow profile

The Grid Convergence Index (GCI) method requires at least three systematic mesh refinements, each requiring the numerical solution to be in the asymptotic range. When the observed order of accuracy differs from the formal order of accuracy, a lack of numerical precision exists which may result in erroneous conclusions. The aim of the work in this paper is to evaluate the effect the mesh resolution for structured hexahedral, unstructured hexahedral and tetrahedral mesh has on the observed order of accuracy and the accuracy of the numerical solution of the mean air flow velocity profile in indoor environments. The GCI value was calculated based on the recommendation of the lower limit of the observed order of accuracy. For the structured hexahedral mesh, with successive grid refinements the observed order of accuracy converges close to the formal order of accuracy, while for the two other unstructured meshes it converges more gradually. The lowest GCI value was obtained when the observed order of accuracy has reached its highest level of accuracy. In this study the RNG k−ε turbulence model was adopted, and when the obtained numerical results were compared with another published numerical study, the comparison showed that the structured hexahedral mesh with RNG k−ε turbulence model produced a similar result to that produced from unstructured hexahedral mesh using the LES turbulence model.