Aseptic Zero Discharge Fluid Dynamic Gauging for Measuring the Thickness of Soft Layers on Surfaces

A bench-top device that can be used to perform fluid dynamic gauging measurements of soft solid layers with zero net liquid discharge and potentially under aseptic (closed system) conditions is demonstrated. Test results are presented for Newtonian liquids with a range of viscosities: deionized water, sucrose solutions, glycerol/water solutions and paraffin oil. The experimental data for discharge coefficient Cd against clearance/nozzle throat diameter gave good agreement with CFD simulations and literature. The influence of surface roughness was studied by making measurements on a series of commercial sandpapers. The rough surfaces gave rise to systematic differences in Cd from those obtained with smooth substrates. Careful calibration is required when gauging rough surfaces.