Paper 28: Laminar Radial Flow between Parallel Plates and its Application to Viscosity Measurements
To supplement viscosity measurements of water made by the more conventional methods, for example by capillary or rotating cylinder viscometers, it was decided to make a ‘radial flow viscometer’ as outlined by H. Gümbel in Barr's ‘Monograph of viscosity’ (1)†. The radial flow viscometer consists principally of two flat discs separated by a known distance, the fluid being forced to flow radially inward and leaving the discs through a hole in the centre of one of the discs. Before the method could be adopted, it was essential to devise a formula which would account for the inertia term in the equation of motion, since disregard of the inertia term would render the final equation inaccurate. An equation has been developed from the Navier-Stokes equations, which gives a solution involving elliptic integrals. An attempt is made to compare the above solution with the well-known creeping flow solution and with experimental results. Preliminary tests for varying flows and varying widths of separation of the discs have shown discrepancies of under 2 per cent between experimental and theoretical values.