dc.contributor.author Tyvand, Peder A. dc.contributor.author Nøland, Jonas Kristiansen dc.date.accessioned 2019-11-19T09:59:42Z dc.date.available 2019-11-19T09:59:42Z dc.date.created 2019-11-10T00:16:00Z dc.date.issued 2019 dc.identifier.citation Transport in Porous Media. 2019, PP (99), . nb_NO dc.identifier.issn 0169-3913 dc.identifier.uri http://hdl.handle.net/11250/2629246 dc.description.abstract The 4th order Darcy-Benard eigenvalue problem for the onset of thermal convection in a 3D rectangular porous box is investigated. We start from a recent 2D model for a rectangle with hand-picked boundary conditions defying separation of variables so that the eigenfunctions are of non-normal mode type. In this paper, the previous 2D model is extended to 3D by a Fourier component with wavenumber $k$ in the horizontal y-direction, due to insulating and impermeable sidewalls. As a result, the eigenvalue problem is 2D in the vertical xz-plane, with k as a parameter. The transition from a preferred 2D mode to 3D mode of convection onset is studied with a 2D non-normal mode eigenfunction. We study the 2D eigenfunctions for a unit width in the lateral y direction to compare the four lowest modes k_m = m \pi~(m=0,1,2,3), to see whether the 2D mode (m=0) or a 3D mode (m >= 1) is preferred. Further, a continuous spectrum is allowed for the lateral wavenumber $k$, searching for the global minimum Rayleigh number at k=k_c and the transition between 2D and 3D flow at k=k*. Finally, these wavenumbers k_c and k* are studied as functions of the aspect ratio. nb_NO dc.description.abstract A Non-normal-mode Marginal State of Convection in a Porous Box with Insulating End-Walls nb_NO dc.language.iso eng nb_NO dc.publisher Springer Verlag nb_NO dc.relation.uri https://link.springer.com/article/10.1007/s11242-019-01361-4 dc.title A Non-normal-mode Marginal State of Convection in a Porous Box with Insulating End-Walls nb_NO dc.type Journal article nb_NO dc.type Peer reviewed nb_NO dc.description.version acceptedVersion nb_NO dc.source.pagenumber 19 nb_NO dc.source.volume PP nb_NO dc.source.journal Transport in Porous Media nb_NO dc.source.issue 99 nb_NO dc.identifier.doi https://doi.org/10.1007/s11242-019-01361-4 dc.identifier.cristin 1745703 dc.description.localcode This is a post-peer-review, pre-copyedit version of an article published in [Transport in Porous Media] Locked until 9.11.2020 due to copyright restrictions. The final authenticated version is available online at: https://doi.org/10.1007/s11242-019-01361-4 nb_NO cristin.unitcode 194,63,0,0 cristin.unitname Fakultet for informasjonsteknologi og elektroteknikk cristin.ispublished true cristin.fulltext postprint cristin.qualitycode 2
﻿