ABSTRACT:

This paper focuses on the simulation of acoustic signatures created by fluid flow through a porous material with the goal of learning physical flow characteristics from flow-generated acoustic signatures. A fluid-solid interaction solver (FSIS), as a part of a combined finite-discrete element (FDEM) software package, is used to perform the simulations. Acoustic signals were recorded at various locations throughout the fluid and solid domains for different inlet velocities. The observed differences in acoustic signals are discussed as a function of the imparted inlet velocity. We find promising observations regarding the relation of the acoustical signal and flow characteristics.

1. Introduction

Fluid flow through porous geomaterials is relevant to a wide variety of geotechnical research topics (e.g., hydrocarbon recovery, earthquake rupture, etc.). Fluid transport through subsurface systems can produce measurable acoustic signatures, and understanding these signatures is critical to improving characterization and prediction of subsurface processes. Previous numerical studies modelled acoustic wave propagation in randomly-packed, dry, granular material to investigate the mechanisms that control wave velocity, dispersion, and attenuation (Zhai et al., 2020). In addition, though indirectly related to this work, modelling of flow through granular beds is common in chemical engineering applications (Carman, 1997). The Discrete Element Method (DEM) has been combined with the fluid conservation equations to study how local microstructure affects energy loss (i.e., pressure drop) in a fixed bed reactor (Dorai et al., 2015). Comprehensive reviews of fixed-bed reactor modelling are provided by Dixon et al., 2006 and Jurtz et al., 2019. As evidenced by the literature, understanding acoustic measures associated with fluid-solid interactions is valuable in a wide range of applications. The ultimate goal of this research is to connect characteristics of fluid flow through a porous system, such as permeability, to the acoustic signals measured in the solid. As a first step, this study explores these relationships by simulating fluid flow through a porous geomaterial and recording changes in the resultant acoustic signature in a nearby solid material as a function of fluid inlet velocity.

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