A non-contact apparatus and method for mapping the wave profile of capillary waves on a fluid surface to determine viscosity of the fluid. Two conducting blades coupled to a sine wave generator are positioned spaced laterally above and near the surface of the fluid to generate a standing capillary wave on the fluid surface between the blades. A laterally moveable fiber optic probe is coupled to a laser to transmit laser light toward the fluid surface and to receive reflected light from the fluid surface. Part of the laser light reflects from the end of the probe and creates an interference pattern with the light reflected from the fluid surface. The light reflected from the end of the probe and from the fluid surface are combined to form an interference signal which is analyzed to obtain the amplitude of the wave directly under the probe. By moving the probe laterally, nodes on the standing wave may be detected to find the wavelength of the capillary wave. One blade may be decoupled from the sine wave generator and the fiber optic probe moved laterally to determine the wave amplitude of a traveling wave as a function of distance which is then used to determine viscosity.
University of Northern Iowa Research Foundation
Behroozi, Feredoon, "Apparatus and method for measurement of fluid viscosity" (2003). Patents (University of Northern Iowa). 12.