Measurement and simulation of pressure drop across replicated porous aluminium in the Darcy-Forchheimer regime

Abstract

Experimental measurements of the pressure drop across porous metals have been compared with computational fluid dynamics simulations, for the first time, for structures typified by large pores with small interconnecting "windows". Structural information for the porous structures was obtained from X-ray computed tomography and a robust methodology for developing a representative volume element is described. The modelling approach used was able to reliably predict the pressure drop behaviour within the Forchheimer regime. The methodology was extended to simulate flow through geometrically-adapted, "semi-virtual" pore structures and this approach could prove to be an invaluable tool in the design of porous metal components for applications involving fluid flow.

The permeability of replicated microcellular structures in the Darcy regime

“…For laminar flow experimental measurements of fluid conducted on microcellular “bottleneck” aluminium foam structures (pore volume fractions from 0.66 to 0.86 and nominal pore size between 108 and 425 μm) made by replication‐casting processes, the permeability predicting theoretical “bottleneck” was extended to model flow beyond Darcy and to show that permeability ( k 0 ), Form drag ( C ), and dimensionless Forchheimer coefficient ( C F ) terms in the Darcy–Dupuit–Forchheimer model (Equation ) are preferentially influenced by the openings (connectivity) than pore diameter sizes. Computational fluid dynamics (CFDs)modeling and simulation of airflow across microcellular structures via tomography datasets in the Forchheimer regime have also been reported in the literature with reasonable fits to experimental data. Figure 2a presents close agreements between experimentally measured and CFD modeled data for samples of similar pore sizes (2.0–2.5) but differentiated by their applied differential pressures during casting; showing a varying degree in the sizes of their pore diameter openings.…”

“…Man‐made porous metallic structures such as steel, nickel, copper, aluminium, and alloys are characterized as sponge‐like shaped cellular materials consisting of a metal frame (solid matrix), air‐filled pores, and interconnecting pores, also known as “windows.” These interconnecting “windows” in cellular metals is considered as an open volume within the metal matrix network that allows a uniform length of passages and distribution. They are classified into open‐celled and close‐celled cellular structures and can be made by different technological processes like additive manufacturing, pressure‐less sintering, replication‐casting route, reactive processing, and gas entrapment techniques .…”

“…Computational fluid dynamics (CFDs)modeling and simulation of airflow across microcellular structures via tomography datasets in the Forchheimer regime have also been reported in the literature with reasonable fits to experimental data. Figure 2a presents close agreements between experimentally measured and CFD modeled data for samples of similar pore sizes (2.0–2.5) but differentiated by their applied differential pressures during casting; showing a varying degree in the sizes of their pore diameter openings. Table presents these changes in pore‐structure related properties and flow information in the inertial dominated flow.…”

“…Though, currently computed values of flow permeability of these structures in the Darcy regime are also presented in Table and would be discussed later. More so, combination of 3D advanced imaging tools and CFD modeling approach in reported in Otaru et al was extended to model the pore‐structure related properties and flow information of “structural‐adapted” bottleneck‐structures (Figure 2b). This enabled comprehensive understanding and an appreciation of the changes in pressure drop developed across these materials attributed to the changes in their pore structure‐related properties within the Forchheimer dominated regime.…”

“…Plots of (a) measured (EXPT) and X‐ray CT modeled (μCT) pressure drop per unit thickness against superficial air inlet velocity at Forchheimer flow regime (Adapted from Reference ) and (b) Plots of simulated pressure drop per unit length for semivirtual structures (structural domain erosion, 1–5 pixel removed) using CT images compared with simulations for near‐equivalent “real” samples (Y3 and Y4)…”