Two hot-wire viscometers

Abstract

Instruments based on the convective cooling of an electrically heated wire, for giving the distribution of velocity across a liquid (a) flowing in a cylindrical tube, (b) flowing in the annular space between two concentric cylinders, one rotating and the other at rest, are described. As examples of their use, the velocity gradients in a number of liquids at various stages between stream-line and turbulent flow are shown, and compared with the forces producing the flow. The use of a hot wire and a string galvanometer to detect unsteady flow is illustrated.