Integrated Fluid Dynamic Gauge for Measuring the Thickness of Soft Solid Layers Immersed in Opaque, Viscous, and/or Non-Newtonian Liquids in Situ

Abstract

A new fluid-dynamic gauging (FDG) device for monitoring the thickness of soft solid layers immersed in liquid in real time and in situ is demonstrated. An inductive proximity sensor is incorporated in the FDG nozzle head to allow the distance between the head and the layer, and an underlying metal substrate, to be determined simultaneously. The concept is demonstrated for copper, mild and stainless steel substrates, for coated substrates, and for liquids spanning a range of opacity and viscosity including water; whole UHT milk and commercial washing-up liquid (both opaque); 1 and 3 wt% CMC solutions (exhibiting non-Newtonian behaviour). The resolution of the inductive sensor was ± 10 μm or better, and was unaffected by the liquid. Computational fluid dynamics simulations using OpenFOAM gave good agreement with experimental discharge coefficients for viscous and non-Newtonian fluids. A short study of the growth of ice crystals from skimmed UHT milk is presented.