Turbulent Flow Control in Composite Porous-Fluid Systems Through Graded Porosity

This paper presents our preliminary findings on the influence of graded porosity on the momentum exchange and heat transfer in a composite porous fluid system, utilizing pore-scale large eddy simulation. We examine two composite porous-fluid systems with identical overall porosity (Φ_Global) of 50%, differing only in local porosity (Φ_Local) configurations — bottom-up grading (20% to 80%) and top-down grading (80% to 20%). Through flow visualization, we observe fluid leakage from porous to non-porous regions across the porous-fluid interface in both cases. Graded porosity proves effective in regulating this phenomenon, introducing geometric constraints on the flow leakage — the primary mechanism governing momentum exchange and heat transfer across the porous-fluid interface. Additionally, distinct characteristics in the development of the turbulent boundary layer on the porous-fluid interface and the turbulent flow structures for the two examined cases, highlight the efficacy of graded porosity as a passive flow control strategy within porous-fluid systems. In conclusion, our research contributes valuable insights into the application of graded porosity for passive flow control in porous-fluid systems.