arXiv subjects

Andrey V Kuznetsov

Publications and source records attributed to Andrey V Kuznetsov.

2 recordsLinked to original sources

arXiv2026

Turbulence Kinetic Energy Distribution and Heat Transfer in a Porous Layer Induced by Bluff Body Vortex Shedding

When a turbulent vortex impinges on a porous layer, it creates a complex multiscale interaction: the wake structures that form in the free fluid engage with the intricate geometry of the pores, and this interplay governs both the turbulent energy budget and the rate of heat transfer. Here we use interface-resolved two-dimensional direct numerical simulations (DNS) to examine how a bluff-body wake impinges on an in-line porous array heated to maintain a constant wall temperature. The Reynolds number is fixed at Re = 10000, and the porosity is varied between $ϕ$ = 0.80 and $ϕ$ = 0.95. In all cases, the incoming von Kármán vortices undergo rapid breakdown at the porous/fluid interface and do not persist as coherent macroscale structures within the porous layer. The interface instead acts as a spectral filter: large-scale wake energy is strongly attenuated, while turbulence is regenerated locally within the matrix via shear layers and microscale vortex shedding around individual obstacles. Thermal statistics show that the lower-porosity medium produces higher local and surface-averaged Nusselt numbers across representative interface and interior locations. This is consistent with the stronger shear and enhanced fluid/solid thermal interaction associated with the larger surface-area-to-volume ratio. These results clarify the mechanisms by which wake-driven turbulence is converted into pore-scale motions and how porosity tunes the balance between turbulence attenuation and convective heat transfer in porous coatings and inserts.

physics.flu-dyn↗

arXiv2025

Symmetry-Breaking of Turbulent Flow in Periodic Porous Media at Intermediate Porosities

This paper presents a novel discovery of a symmetry-breaking effect in porous media with porosity between 0.8-0.9, which we are referring to as the intermediate porosity flow regime. Using large eddy simulation, we studied how heat transfer and turbulent convection occurs within these materials at a microscopic level. We observed symmetry-breaking in porous structures made of regularly spaced circular cylinders, a common design in heat exchangers, immediately following the laminar to turbulent flow transition between Reynolds numbers of 37 and 100. Asymmetric patterns persisted up to Reynolds numbers of 1,000. The initial breakdown of symmetry occurs through a Hopf bifurcation, creating an oscillating flow pattern as shear layers interact around the solid obstacles. When the flow becomes turbulent, random variations in the timing of vortex oscillations (caused by the secondary instability) create asymmetric distributions of fluid velocity and temperature throughout the porous space. This leads to the formation of alternating channels with high and low velocity fluid flow. At the macroscale level, this loss of symmetry creates residual transverse drag force components and asymmetric heat flux distribution on the solid obstacle surfaces. Interestingly, the oscillating flow pattern promotes attached flow on the circular cylinder surfaces, which enhances heat transfer from the cylinders to the fluid. We observe that this secondary flow instability is the primary mechanism of enhanced turbulent heat flux from porous media with circular cylinders compared to those with square cylinders.

physics.flu-dyn↗