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Impact Of Porous-Media Topology On Turbulent Fluid Flow: Time-Resolved PIV Measurements

J. Härter, R. Poser, B. Weigand, G. Lamanna

Institute of Aerospace Thermodynamics, University of Stuttgart, Germany

An investigation of the interactions between a turbulent duct flow above a 3D porous medium with a periodic topology is reported. Both spatially and temporally resolved point measurements of velocity in the free flow and at the interface of the porous medium using the Particle Image Velocimetry (PIV) technique are presented. A Schwarz Primitive triply periodic minimal surface (TPMS) with a frequency of f = Π/20 printed from polyamide PA12 with a porosity of ϕ = 0.92 was investigated as a porous structure. The periodicity of the model results in two different topologies, hill- and valley-alignment, each of which represent a measurement plane. These different alignments show a strong influence on the turbulent flow above the porous me dium. In addition to the time-averaged velocity field for the two alignments, velocity profiles as well as turbulent kinetic energy profiles at selected positions in flow direction are also shown. The influence of the turbulent channel flow on the porous model is shown by a contour plot of the time-resolved velocity, where this represents the turbulent fluctuation at a point in t ime. For the time-resolved plot, the same influence of the different topology to the respective alignments is shown. With these time-resolved measurements, transient flow processes could be resolved, such as the detachment and attachment of the flow to the porous surface, which are also shown in this paper. These measurements provide an insight into the mechanism of energy, mass and momentum transfer at the interface between the free stream and the porous medium. The results presented are useful for further understanding of turbulent flows on flush mounted complex 3D structures and the influence of the periodic surface on the free flow.

20th Edition
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