4D Synchrotron X-Ray Multi Projection Imaging (XMPI) for studying multiphase flow dynamics and flow instabilities in porous networks

TL;DR

This paper introduces a novel synchrotron X-ray multi-projection imaging technique that captures four-dimensional multiphase flow dynamics in porous media at high spatial and temporal resolution, overcoming limitations of traditional tomography.

Contribution

The study demonstrates the first application of XMPI for real-time 4D imaging of flow in porous networks without high rotational speeds, enabling direct comparison with simulations and revealing current modeling limitations.

Findings

Successful 4D imaging of flow instabilities at 50 Hz

Qualitative agreement with multiphase simulations

Identification of discrepancies in contact-line dynamics

Abstract

Flow instabilities such as Haines jumps in porous media are common phenomena that occur on sub-second timescales. X-rays are particularly suitable for investigating these processes because they provide non-destructive three-dimensional insight into the network structure and the liquid distribution within porous media. Studying imbibition events in four dimensions (three spatial dimensions plus time) is inherently challenging with conventional tomography because the required rapid sample rotation imposes significant centrifugal forces that alter the flow. Here, we demonstrate synchrotron X-ray multi-projection imaging (XMPI) to capture four-dimensional flow in an additively manufactured, homogeneous spherical pore network at 1.3 $\mu$m effective pixel size and 50 Hz temporal resolution without the need for high rotational speeds. This enables in situ visualization of non-repeatable pore-scale events in both space and time, a capability unachievable with classical X-ray tomographic approaches. We compare the results to Shan-Chen multiphase Lattice Boltzmann simulations performed on the same geometry, finding both qualitative agreements and systematic differences in filling sequences and timescales. These discrepancies expose key limitations of current simulation methods in representing contact-line dynamics and realistic boundary conditions limitations that XMPI can directly overcome. By enabling high-resolution, real-time imaging of flow instabilities in opaque porous media, synchrotron XMPI provides a unique platform that bridges the gap between pore-scale experiments and simulations.