A scanning fluid dynamic gauging technique for probing surface layers

Abstract

Fluid dynamic gauging (FDG) is a technique for measuring the thickness of soft solid deposit layers immersed in a liquid environment, in situ and in real time. This paper details the performance of a novel automated, scanning FDG probe (sFDG) which allows the thickness of a sample layer to be monitored at several points during an experiment, with a resolution of ±5 μm. Its application is demonstrated using layers of gelatine, polyvinyl alcohol (PVA) and baked tomato purée deposits. Swelling kinetics, as well as deformation behaviour-based on knowledge of the stresses imposed on the surface by the gauging flow-can be determined at several points, affording improved experimental data. The use of FDG as a surface scanning technique, operating as a fluid mechanical analogue of atomic force microscopy on a millimetre length scale, is also demonstrated. The measurement relies only on the flow behaviour, and is thus suitable for use in opaque fluids, does not contact the surface itself and does not rely on any specific physical properties of the surface, provided it is locally stiff.

Using the Scanning Fluid Dynamic Gauging Device to Understand the Cleaning of Baked Lard Soiling Layers

“…5) was developed by Gordon et al [16]. The sFDG device collects sample thickness data continuously, to an accuracy of 15 m.…”

“…The scanning fluid dynamic gauge (sFDG) is an automated FDG device with computer-controlled movements, and uses a feedback loop to guide the nozzle to track the layer during swelling and cleaning at several locations [16]. The sFDG device has accuracy of 15 m and can operate at solution temperatures of up to 60 C [16].…”

“…The sFDG device has accuracy of 15 m and can operate at solution temperatures of up to 60 C [16]. The device can also study cleaning in situations where the substrate temperature is different from that of the bulk fluid.…”

“…Rigorous characterisation of the layer material was difficult, as it was insoluble in most solvents. Cleaning was studied using the scanning fluid dynamic gauging technique developed by Gordon et al (Meas Sci Technol 21:85–103, 2010), which provides non-contact in situ measurement of layer thickness at several sites on a sample in real time. Tests at 50 C with alkali (sodium hydroxide, pH 10.4–11) and three surfactant solutions indicated two removal mechanisms, related to the (1) roll-up and (2) dispersion mechanisms reported for oily oils, namely (1) penetration of solvent at the soil–liquid interface, resulting in detachment of the soil layer as a coherent film, observed with linear alkylbenzene sulfonic acid (LAS) and Triton X-100 and aqueous sodium hydroxide at pH 10.4–11; and (2) the breakdown promoted by the agent penetrating through the layer, observed with cetyl trimethyl ammonium bromide (CTAB), in which CTAB antagonised the cleaning action of LAS.…”

Dynamic Gauging of Soft Fouling Layers on Solid and Porous Surfaces

“…Der Massenstrom m ist im Allgemeinen im Bereich 0 < h/d t < 0,25 sensitiv zum Abstand h und ermöglicht somit dessen Berechnung. Die Dicke der Ablagerung d wird dann bestimmt mit d = h 0 -h. Eine computerunterstützte Ansteuerung der Düse ermöglicht die automatische Messung nacheinander an mehreren Positionen mit einer Genauigkeit von ±5 lm [3]. Dabei sind die Hauptquellen der Messunsicherheit die Volumenstrommessung (±1 %) und die Düsenposition des induktive Sensors (±1 lm).…”