1998 Volume 12 Issue 1 Pages 81-84
A film flowing on a wall exhibits as many distinct wave features. The produced interfacial waves show fascinating non-linear phenomena, including solitary waves and complex disordered patterns. Abundant measurements have been made of these phenomena using electrical resistance or electrical-capacity methods, optical methods, and laser beam methods. In this paper, a new way of measurement of the interfacial waves is presented using laser focus displacement meters which allow accurate measurements of film thickness in real time with a sensitivity of 2 microns and 1 kilohertz. With this method, detailed information on the waves was obtained on a film flowing down a vertical wall in an entry region. The measured average film thickness and wave velocity agreed with that calculated using Nusselt's law, indicating the flow to be laminar in the entry region even at a high flow rate. Research on multifluid with progress and improvement in microscopic measuring is expected to be conducted increasingly in the future.