Verification of Laminar and Transitional Flow Simulations in Porous Media with Nek5000

Open Access
Author:
Holler, David Michael
Graduate Program:
Nuclear Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
None
Committee Members:
  • Kostadin Nikolov Ivanov, Thesis Advisor
  • Maria Nikolova Avramova, Thesis Advisor
Keywords:
  • verification
  • laminar flow
  • transitional flow
  • porous media
  • incompressible
  • Nek5000
  • computational fluid dynamics
  • CFD
  • open source
Abstract:
This thesis is a numerical study of laminar flow through a microscopic section of porous media using simulations performed by the computational fluid dynamics solver Nek5000. The theoretical origins of Nek5000 are discussed, as well as the methods utilized to compute solutions. Motivations for this research, including porous media model implementation and selected reactor core design, are discussed. A literature review was conducted in order to determine the current level of work being done in this field. Most of the current efforts are aimed towards understanding turbulence, since the laminar regime is much more understood. Laminar and transitional relations for porous media parameters are presented and evaluated for a unit cell created with Nek5000 using the already included meshing utility. The mesh contained 2,304 spectral elements, with a polynomial order of 7 and an integration order of 11 for the convective terms. All results show strong correlation to the applied Reynolds number, none of which are linear. The reduced pressure drop, permeability, and form coefficient were found to have strong correlations in the laminar region (Re < 0.1). All three parameters had weaker correlations in the regions of transition (Re > 0.1). The transition from viscous to form drag dominated flow is predicted to occur at a Reynolds number of 8, which is within an order of magnitude of the prediction of the onset of transition by the other three parameters. The results of this thesis are then compared with the solutions to potential flow, and show little departure from the expected velocity profiles. Conclusions and recommendations follow, where it is suggested that this study be redone with more geometry refining and also evaluated with a turbulence model.