Numerical Investigation of the Three-Dimensional Flow around a Surface-Mounted Rib and the Onset of Unsteadiness

Vassilios N. Laskos, Thomas Kotsopoulos, Dimitrios Karpouzos and Vassilios P. Fragos ()
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Vassilios N. Laskos: Laboratory of Agricultural Structures & Equipment, Department of Hydraulics, Soil Science and Agricultural Engineering, School of Agriculture, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece
Thomas Kotsopoulos: Laboratory of Agricultural Structures & Equipment, Department of Hydraulics, Soil Science and Agricultural Engineering, School of Agriculture, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece
Dimitrios Karpouzos: Laboratory of Agricultural Structures & Equipment, Department of Hydraulics, Soil Science and Agricultural Engineering, School of Agriculture, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece
Vassilios P. Fragos: Laboratory of Agricultural Structures & Equipment, Department of Hydraulics, Soil Science and Agricultural Engineering, School of Agriculture, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece

Mathematics, 2023, vol. 11, issue 12, 1-18

Abstract: The incompressible laminar isothermal flow of a Newtonian fluid at steady state around a surface-mounted rib is studied in a three-dimensional (3D) numerical experiment. The dimensionless Navier–Stokes equations are solved numerically using the Galerkin finite element method for Reynolds numbers 1 to 800. The expansion ratio of the problem is 1:9.6, while the aspect ratio is 1:20. The transition from the steady to the unsteady state and the identification of the critical Reynolds number are investigated in this paper. Numerical results of the skin-friction lines at the bottom and streamlines throughout the computational field are presented. A comparison between the 2D and 3D flow is made to show the effect of the walls on the flow, which reaches the plane of symmetry and affects the flow there; hence, also affecting the stability of the flow. It is concluded that the flow is three-dimensional even for a Reynolds number equal to 10. The critical Reynolds number is 600, and the steady-state equations can be used for any calculations up to this value.

Keywords: Galerkin finite elements; 3D-rib; Navier–Stokes equations; streamlines; skin-friction lines (search for similar items in EconPapers)
JEL-codes: C (search for similar items in EconPapers)
Date: 2023
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