Rheometry based on free surface velocity

Abstract

This paper explores the possibility of identifying the rheology of a fluid by monitoring how the free surface velocity field is affected by a perturbation in the flow. The dam-break problem is considered which results from the release of a gate initially separating two fluid pools of different depth. The flow velocity is measured by seeding the free surface with buoyant particles and using Particle Tracking Velocimetry. In parallel, a mathematical model based on the lubrication approximation for fluids with a power-law rheology is developed. The model is validated against a similarity solution which is obtained for the spreading of a gravity current under its own weight and neglecting surface tension. Minimizing the difference between the free surface velocity fields obtained numerically and measured experimentally enables the identification of rheological parameters. The methodology is tested on ideal and noisy synthetic data sets and experimental data obtained with aqueous glycerol.

Identification of Ellis rheological law from free surface velocity

“…Sellier (2016) reviewed earlier studies describing methods to infer the rheology of a fluid from free surface data. In a recent contribution, we have shown that it is possible to identify the two parameters of a power-law rheology by minimising the differ-ence between the measured and simulated free surface velocity field for the dam-break flow problem Al-Behadili et al (2018).…”

“…The power-law rheology is however quite restrictive and is un-20 able to describe the behaviour of many fluids, particularly for low shear values Myers (2005). In this paper, we therefore aim to demonstrate that it is possible to extend the methodology described in Al-Behadili et al (2018) to identify the parameters of an Ellis rheological law which is more versatile since it is and Schwartz (1994); Myers (2005) and for three-dimensional flow in Schwartz and Eley (2002); Kheyfets and Kieweg (2013).…”

Rheology of Un-Sieved Concentrated Domestic Slurry: A Wide Gap Approach

“…These non-conventional methods usually stem from the limitations of rheometric techniques, rheological measurements from the engineering application itself, and the need for inline measurements. Some of the non-conventional techniques to estimate the rheology are through free surface velocity of the fluid flow [5], flow from spreading of a fluid from gravity currents [6], flow in a narrow channel [7], and ultrasound image velocimetry of flow in pipes [8].…”