MEASUREMENTS OF INTERFACIAL WAVES ON A FILM FLOWING DOWN WALL USING LASER FOCUS DISPLACEMENT METERS AND AN IMAGE-PROCESSING METHOD

摘要

Waves on a film flowing down a vertical wall show fascinating nonlinear phenomena, including solitary waves and complex disordered patterns. Many studies of the structure and dynamic characteristics of waves have therefore, been carried out to clarify the phenomena. In a previous study, we measured interfacial waves on a film flowing down a vertical plate wall using laser focus displacement meters (LFDs, Keyence Model LT-8100) which were developed to detect scratches on ICs or other electronic devices. The results showed that LFDs made possible accurate measurements of the structure and velocity of interfacial waves. Details of the development of the film flowing down a vertical plate were clarified using LFDs. In this study, simultaneous measurements of interfacial waves on a film flowing down a plate wall were carried out using the LFDs and an image-processing method in an entry region. Wave velocity was calculated in the LFD measurement from the time delay between two signals provided by LFDs, and in the image-processing method from the travel distance of the wave crest. As a result, we clarified the dynamic characteristics of the interfacial waves. The vertical wave velocities obtained by the image-processing method agreed well with those obtained by LFDs. A theoretical equation calculated by Nusselt's law accurately predicted the measured velocities in an entry region. Measurements of the horizontal wave velocity component were made possible by the image-processing method.