An Experimental Setup to Investigate Non-Newtonian Fluid Flow in Variable Aperture Channels

Alessandro Lenci,Luca Chiapponi

doi:10.3390/w12051284

Abstract

Non-Newtonian fluid flow in porous and fractured media is of considerable technical and environmental interest. Here, the flow of a non-Newtonian fluid in a variable aperture fracture is studied theoretically, experimentally and numerically. We consider a shear-thinning power-law fluid with flow behavior index n. The natural logarithm of the fracture aperture is a two-dimensional, spatially homogeneous and correlated Gaussian random field. An experimental device has been conceived and realized to allow the validation of the theory, and several tests are conducted with Newtonian and shear-thinning fluids and different combinations of parameters to validate the model. For Newtonian fluids, experimental results match quite well the theoretical predictions, mostly with a slight overestimation. For non-Newtonian fluids, the discrepancy between experiments and theory is larger, with an underestimation of the experimental flow rate. We bear in mind the high shear-rates involved in the experiments, covering a large range where simple models seldom are effective in reproducing the process, and possible interferences like slip at the wall. For all test conditions, the comparison between analytical and numerical model is fairly good.

Highlights

A number of engineering activities on geological formations involve the use of chemical solutions and mixtures of liquids and solid particles
In this paper we present experimental results on Ostwald–deWaele fluids, to validate the available models of power-law fluids in statistically varying fractures, including the recent extension to truncated power-law fluids recently proposed in Felisa et al [15]
A plate of Aluminum 1000 × 250 mm2 and 20 mm thick was machined with a computer numerical control (CNC) tool in order to shape the lower surface of the variable aperture fracture

Summary

Introduction

A number of engineering activities on geological formations (e.g., enhanced oil recovery, soil remediation, drilling operations) involve the use of chemical solutions and mixtures of liquids and solid particles. As well as heavy oil, stimulant fluids and cement mixtures, have particular rheological behavior: they can resemble yield-stress fluids for very low shear rates, and generally show shear-thinning or shear-thickening behavior. Drilling muds, which are ubiquitous in underground applications, are mixtures of water emulsified with oil, clay, weighting material, small amounts of salts and polymeric fluids, and at low cutting speed have a very high apparent viscosity [1], resembling Bingham fluids. A renewed interest towards aqueous foams and their flow in porous media, has stimulated the investigation of non-Newtonian fluids in heterogeneous media [2]. Foams, which can be modeled as shear-thinning fluids, are often used in hydraulic fracturing to saturate fractures, and allow the generation of high-gradient pressure to divert the

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Conclusion