Exploring the impact of unit cell size on fluid dynamics in lattice structures: Experimental and numerical insights

• Effect of the cell size and orientation on the pressure drops in lattice structure • The ratio of permeability and square of the hydraulic diameter is constant • The Forchheimer coefficient is not affected by the cell size • The friction factor is independent of the Reynolds number and the cell size. Advanced manufacturing techniques have made it possible to customize the geometry of solids unit cells, creating various architected materials. One type of such material is the strut or surface-based lattice. In this work, we investigated fluid flow through two lattice structure topologies, body-centered cubic ( bcc ) and face-centered cubic with vertical strut ( f 2 ccz ). The goal is to understand the effect of the unit cell size and cell orientation on pressure drops and permeability. By doing this, we aim to clarify how the scale of the unit cell influences the treatment of lattice structures as porous media. Through the experimental campaign, we characterized the pressure drops across these structures and performed dimensionless analyses of the measurements. The investigation involved a numerical model to simulate fluid flow behavior at low velocities and determine permeability using the Darcy equation. Finally, we coupled the experimental results with numerical simulations to assess the inertial coefficient in the Darcy-Forchheimer correlation. The results showed that, given the cell topology, porosity and flow direction, it is possible to uniquely determine the relationship between velocity and pressure losses as a function of hydraulic diameter. Additionally, the permeability ratio to the square of the hydraulic diameter, with fixed topology, porosity and flow direction, resulted in a constant.