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 nonporous 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.